TWI435369B - Excimer lamp - Google Patents

Description

Excimer lamp

The present invention relates to an excimer lamp used for treating a surface to be processed by a surface treatment such as a cleaning treatment, an ashing treatment, a film formation treatment, or the like by irradiation with ultraviolet rays.

In the glass substrate of the liquid crystal display device, the object to be processed such as a semiconductor wafer, vacuum ultraviolet light having an ultraviolet ray having a wavelength of 200 nm or less is developed, and the vacuum ultraviolet light and the ozone generated thereby are processed. In the technique of the treatment body, for example, a cleaning treatment technique for removing an organic contaminant adhering to the surface of the object to be processed, or an oxide film formation treatment technique for forming an oxide film on the surface of the object to be processed, has been developed and put into practical use.

As an apparatus for irradiating vacuum ultraviolet light, for example, excimer light which emits vacuum gas by applying a discharge gas in a discharge vessel formed by a medium, and applying an alternating high voltage via a discharge vessel to generate an excimer discharge is used. Excimer lamp. In such an excimer lamp, many attempts have been made to efficiently emit higher intensity ultraviolet rays.

Specifically, it is disclosed that the ultraviolet reflecting layer is formed on the inner surface of the discharge vessel of the excimer lamp, and the ultraviolet reflecting layer is formed by laminating fine particles that transmit ultraviolet rays, such as only cerium oxide or cerium oxide. Other fine particles such as alumina, magnesium fluoride, calcium fluoride, lithium fluoride, magnesium oxide, and the like (see Patent Document 1).

In the excimer lamp of such a configuration, ultraviolet rays that are not directly emitted toward the light emitting portion in the ultraviolet rays generated in the discharge vessel are incident on the ultraviolet reflecting layer, and are formed by the plurality of fine particles constituting the ultraviolet reflecting layer. The surface is repeatedly refracted and reflected, diffused and reflected, and emitted from the light emitting portion. Thereby, ultraviolet rays can be efficiently emitted.

Among the lamps that emit ultraviolet rays, as the material constituting the discharge vessel, for example, ceria glass is widely used. Therefore, the fine particles constituting the ultraviolet ray reflection layer are prevented from being different from the thermal expansion coefficient of the cerium oxide glass constituting the discharge vessel, or are formed to be extremely small, and the adhesion of the ultraviolet ray reflection layer to the cerium oxide glass is increased. The bismuth oxide glass of the same material as the discharge vessel is preferred.

The surface-treated object is a flat shape of a glass substrate such as a liquid crystal panel. Therefore, the excimer lamp formed by the flat discharge vessel having the same light-emitting portion and the object to be processed reduces the gap between the light-emitting portion and the workpiece, thereby suppressing the absorption of ultraviolet rays by oxygen, and thus is efficient. The surface can be surface treated. As an excimer lamp formed by the discharge vessel of such a shape, for example, Patent Document 2 discloses an excimer lamp formed by a rectangular discharge vessel.

The excimer lamp formed as a discharge vessel having a flat light emitting portion has a structure as shown in Fig. 7. The excimer lamp 10 is composed of a flat rectangular discharge vessel 20 made of ceria glass, and the discharge vessel 20 has a structure in which the upper wall plate 21, the lower wall plate 22, the side wall plate 23, and the end wall plate 24 are joined. The discharge gas is sealed inside. Further, the upper surface of the upper wall plate 21 is provided with a high voltage supply electrode 11, and the outer surface of the lower wall plate 22 is provided with a ground electrode 12, and the electrodes 11, 12 are disposed to face each other. The excimer light emission generated in the discharge space S is emitted to the outside through the lower wall plate 22 having the light emitting portion.

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

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

However, in an excimer lamp having an ultraviolet reflecting layer, if the lighting is performed for a long time, the illuminance maintenance rate gradually decreases gradually. Therefore, for example, when surface treatment such as a washing treatment is performed, even if it is intended to be treated with a certain illuminance, there is a problem that the processing ability of the excimer lamp changes with the lighting time.

The present invention has been made in view of the above problems, and an object of the invention is to provide an ultraviolet reflecting layer which can suppress the decrease in illuminance even when lighting for a long period of time, and can efficiently emit vacuum ultraviolet light. Molecular lamp.

The excimer lamp according to the first aspect of the present invention is a discharge vessel including a cerium oxide glass having a discharge space, and a pair of electrodes are provided in a state in which the bismuth oxide glass forming the discharge vessel is interposed, and An excimer lamp in which a discharge gas is sealed in a discharge space and an ultraviolet reflection layer is formed on an inner surface of the discharge vessel, wherein the ultraviolet reflection layer is made of cerium oxide containing an OH group. The OH group concentration in the cerium oxide particles constituting the ultraviolet ray reflecting layer higher than the particles and the melting point is 10 wtppm or more.

According to a second aspect of the present invention, in the first aspect of the invention, the cerium oxide particles constituting the ultraviolet ray reflective layer have a OH group concentration of 502 wtppm or less.

By mixing fine particles having a melting point higher than that of cerium oxide in the ultraviolet reflecting layer, it is possible to prevent the fine particles adjacent to each other from being bonded to each other and to disappear the grain boundary, thereby suppressing the decrease in the reflectance of the ultraviolet reflecting layer.

In addition, the cerium oxide particles constituting the ultraviolet ray reflecting layer contain an OH group, thereby suppressing generation of internal defects in the cerium oxide particles contained in the ultraviolet ray reflecting layer, thereby preventing light absorption in the ultraviolet region due to the ultraviolet ray reflecting layer. The reflectance of the ultraviolet reflecting layer is maintained, the degree of illuminance reduction of the excimer lamp is suppressed, and the vacuum ultraviolet light is efficiently emitted.

In addition, when the concentration of the OH group in the cerium oxide particles constituting the ultraviolet ray-reflecting layer is 10 wtppm or more, the reflection retention ratio and the illuminance maintenance ratio can be maintained at a high value, and the illuminance maintenance at the time of long-time lighting is excellent in advance. Effect.

When the concentration of the OH group in the cerium oxide particles constituting the ultraviolet ray reflecting layer is 502 wtppm, the oxygen atoms generated from the OH group are excessively present in the discharge space, and the oxygen atoms react with the rare gas atoms. The formation of molecules hinders the illuminance maintenance rate of the excimer lamp, and the vacuum ultraviolet light can be efficiently emitted.

1 is a cross-sectional view for explaining an outline of an example of an example of the excimer lamp 10 of the present invention. Fig. 1(a) is a cross-sectional view showing a cross section along the longitudinal direction of the discharge vessel 20, and Fig. 1(b) is a cross-sectional view showing a line A-A' of Fig. 1(a).

The excimer lamp 10 is a hollow-length discharge vessel 20 having a rectangular cross section in which both ends are hermetically sealed and a discharge space S is formed inside. The discharge vessel 20 is composed of an upper wall plate 21 and a lower wall plate 22 opposite to the upper wall plate 21, and a pair of side wall plates 23 connected to the upper wall plate 21 and the lower wall plate 22, and the upper wall The plate 21, the lower wall plate 22, and the pair of side wall plates 23 are formed by sealing a pair of end wall plates 24 provided at both ends of the rectangular tubular body. The discharge vessel 20 is formed of cerium oxide glass, such as synthetic quartz glass, which transmits vacuum ultraviolet light well.

Inside the discharge vessel 20, a discharge gas is sealed by press-fitting at, for example, 10 to 80 kPa. Even if any gas is selected as the discharge gas, there is no influence on the temporal change of the radiation intensity, but the center wavelength of the emitted excimer light emission is different by the type of the discharge gas. For example, in an excimer lamp sealed with xenon (Xe), excimer light emission with a center wavelength of 172 nm is generated, and an excimer lamp sealed with a mixed gas of argon (Ar) and chlorine (Cl) is generated. Excimer light having a center wavelength of 175 nm, and an excimer lamp sealed with a mixed gas of krypton (Kr) and iodine (I), emits excimer light having a center wavelength of 191 nm, and argon (Ar) and fluorine are enclosed therein. The excimer lamp of the mixed gas of (F) generates an excimer wavelength having a wavelength of 193 nm as a center wavelength, and an excimer lamp in which a mixed gas of krypton (Kr) and bromine (Br) is enclosed, and 207 nm is generated as a center. Excimer light having a wavelength of excimer light, excimer light having a mixed gas of krypton (Kr) and chlorine (Cl) is generated, and excimer light having a center wavelength of 222 nm is generated.

The outer surface of the upper wall plate 21 of the discharge vessel 20 is provided with a high voltage supply electrode 11, and the outer surface of the lower wall plate 22 is provided with a ground electrode 12, and these electrodes 11, 12 are disposed to face each other. Such electrodes 11 and 12 have a mesh structure and are capable of transmitting light from between the meshes. As the material, for example, aluminum, nickel, gold, or the like is used, for example, by screen printing or vacuum evaporation. Further, each of the electrodes 11 and 12 is connected to an appropriate high-frequency power source (not shown).

In the excimer lamp 10, in order to efficiently utilize the vacuum ultraviolet light generated by the excimer discharge, the ultraviolet reflective layer 30 formed by the particle deposition body is provided on the inner surface of the discharge space S with respect to the discharge vessel 20. . Specifically, it is formed in the field of the high voltage supply electrode 11 corresponding to the inner surface of the upper wall plate 21, and on the inner surface of the upper wall plate 21 and the lower wall plate 22 which are deviated from the fields corresponding to the electrodes 11, 12. And an area in the inner surface of the side wall panel 23 and the end wall panel 24, the ultraviolet reflecting layer 30 is formed.

On the other hand, the lower wall plate 22 of the discharge vessel 20 constitutes a light emitting portion by not forming the ultraviolet reflecting layer 30 corresponding to the inner surface of the ground electrode 12.

The ultraviolet ray reflection layer 30 is composed of, for example, 5 to 1000 μm thick particles composed of cerium oxide particles and fine particles having a melting point higher than that of cerium oxide and transmitting ultraviolet rays. The fine particles having a melting point higher than that of cerium oxide and transmitting ultraviolet rays are, for example, alumina, lithium fluoride, magnesium fluoride, calcium fluoride, barium fluoride or the like. Further, as a material for absorbing ultraviolet rays, for example, titanium or zirconium is used, and such compounds are not used as fine particles. However, as the impurity of the ultraviolet ray reflection layer 30, titanium or zirconium may be mixed.

The ultraviolet ray reflection layer 30 formed by the vacuum ultraviolet light incident on the fine particles transmitting the ultraviolet ray is partially reflected on the surface of the fine particles, and a part is refracted and transmitted to the inside of the particles, and is re-reflected or refracted on the other surface. In the plurality of fine particles, the vacuum ultraviolet light is diffused and reflected by repeating such reflection and refraction.

However, the cerium oxide particles are melted by the heat of the plasma generated in the excimer lamp 10, the grain boundaries are eliminated, and the vacuum ultraviolet light cannot be diffused and reflected, and the reflectance is lowered. On the one hand, the fine particles whose melting point is higher than that of cerium oxide are not melted even when exposed to heat depending on the plasma. Therefore, in the ultraviolet ray reflection layer 30, by mixing fine particles having a higher melting point than cerium oxide, the mutually adjacent fine particles are bonded to each other to prevent the grain boundary from disappearing, and the reflectance of the ultraviolet ray reflection layer 30 can be suppressed. The reduction.

The fine particles included in the ultraviolet ray reflection layer 30 are particle diameters as defined below, and are, for example, in the range of 0.01 to 20 μm, the center particle diameter (the maximum value of the number-based particle size distribution), and in the ultraviolet ray reflection layer 30, For example, it is preferably 0.1 to 10 μm, more preferably 0.1 to 3 μm.

Here, the "particle diameter" means that an approximately intermediate position in the thickness direction of the cross section when the surface of the ultraviolet ray reflection layer 30 is cut in the vertical direction is used as an observation range, and an enlarged projection is obtained by a scanning electron microscope (SEM). For example, the Freit diameter of the parallel line when the arbitrary particles of the projected image are enlarged by two parallel lines in a certain direction.

In addition, the "central particle size" is a range of the particle diameters of the maximum and minimum particle diameters of the particle diameters obtained as described above, for example, in a range of 0.1 μm, and is divided into, for example, 15 It is distinguished that the number of particles (degrees) belonging to each division becomes the center value of the largest division.

In the excimer lamp 10, when the lighting power is supplied to the high voltage supply electrode 12, excimer discharge occurs in the discharge space S between the electrodes 11 and 12 via the discharge vessel 20. Thereby, while the excimer is formed, vacuum ultraviolet light is emitted from the excimer molecule. A part of the vacuum ultraviolet light generated in the discharge space S is directly emitted to the outside through the lower wall 22 having the light emitting portion. Further, a part of the vacuum ultraviolet light is radiated in the direction toward the upper wall plate 21, but the ultraviolet ray reflection layer 30 is diffused and emitted, and is emitted to the outside through the light emitting portion.

The cerium oxide and other fine particles constituting the ultraviolet ray reflection layer 30 have a particle diameter which is the same as the wavelength of the vacuum ultraviolet light, and can efficiently diffuse and reflect the vacuum ultraviolet light.

However, when the excimer lamp 10 including the ultraviolet ray reflection layer 30 was turned on for a long period of time, the initial illuminance could not be maintained, and it was confirmed that the illuminance was gradually lowered with the lighting time. The inventors have reviewed the cause of the decrease in illuminance from all aspects, and have considered whether or not the reflectance of the ultraviolet ray reflection layer 30 which is one of the main causes is lowered.

Here, the reflection intensity spectrum of the ultraviolet-ray reflection layer 30 of the excimer lamp 10 at the initial stage of lighting and the reflection intensity spectrum of the ultraviolet-ray reflection layer 30 of the excimer lamp 10 after long-time lighting are measured, and both are comparatively analyzed. As a result, in the ultraviolet ray reflection layer 30 of the excimer lamp 10 after the long-time lighting, the absorption band generates an ultraviolet region, and it is understood that a part of the ultraviolet ray is absorbed in the ultraviolet ray reflection layer 30 to cause a decrease in illuminance.

The absorption band generated in the ultraviolet region of the ultraviolet ray reflection layer 30 is such that the cerium oxide particles constituting the ultraviolet ray reflection layer 30 are exposed to ultraviolet rays or plasma during discharge, and are subjected to radiation damage to generate wavelengths absorbing ultraviolet rays. The internal defects of light, while the ultraviolet rays are absorbed in internal defects, so that the diffuse reflection is suppressed. The internal defect refers to the Si-O-Si bond of the cerium oxide particles exposed to ultraviolet rays or plasma, the Si-Si defect having an absorption end near a wavelength of 163 nm, or the E'center having an absorption band at a wavelength of 215 nm (Si‧ ).

For the reason described above, the internal defect that generates light that absorbs the wavelength in the ultraviolet region is cerium oxide particles, and the light absorption at the wavelength in the ultraviolet region, which causes illuminance reduction, may depend on the internal defects of the cerium oxide particles. In addition, fine particles of ultraviolet rays other than cerium oxide particles formed by transmitting alumina, lithium fluoride, magnesium fluoride, calcium fluoride, or cesium fluoride do not cause radiation damage even when exposed to ultraviolet rays or plasma. . Therefore, by preventing internal defects from occurring in the cerium oxide particles constituting the ultraviolet ray reflection layer 30, it is possible to suppress a decrease in illuminance, and it is possible to maintain a high illuminance maintenance ratio even when lighting for a long period of time.

In order to prevent internal defects in the cerium oxide particles, it is effective to contain OH groups in the cerium oxide particles. By containing an OH group, it is possible to suppress the occurrence of internal defects in the ceria particles contained in the ultraviolet ray reflection layer 30, and it is possible to prevent the reflectance of the ultraviolet ray reflection layer 30 from being lowered.

Hereinafter, a method of forming the ultraviolet ray reflection layer 30 formed of fine particles containing OH group-containing cerium oxide particles will be described. The ultraviolet ray reflection layer 30 is formed by a method called a "flow down method" in which a particle deposition layer containing cerium oxide particles is formed in a predetermined region of the inner surface of the discharge vessel forming material. For example, in a solvent having a viscosity in which water and a PEO resin (polyethylen oxide) are combined, fine particles are mixed to adjust the dispersion, and the dispersion is introduced into the discharge vessel forming material. Further, after the dispersion liquid is adhered to a predetermined region of the inner surface of the discharge vessel forming material, the water and the PEO resin are evaporated and dried to form a particle deposition layer. Here, the baking temperature is, for example, 500 ° C to 1100 ° C.

As an example of a method in which the cerium oxide particles contain an OH group, the cerium oxide particles not containing an OH group are supplied with water vapor while being heated by an electric furnace (for example, 1000 ° C) to prepare a OH group containing a large amount of OH groups. The case of cerium oxide particles. By using the cerium oxide particles thus treated, the ultraviolet ray reflection layer 30 composed of fine particles containing OH group-containing cerium oxide particles can be formed.

Further, as another method, after the cerium oxide particles not containing an OH group are attached to a predetermined region of the inner surface of the discharge vessel forming material, the cerium oxide particles may be contained in the cerium oxide particles by firing while supplying water vapor. base. Further, after the ultraviolet ray blocking layer 30 is formed by firing the cerium oxide particles not containing an OH group, the cerium oxide particles may be contained in the cerium oxide particles by heating the electric furnace while supplying water vapor.

Further, since the commercially available cerium oxide particles are obtained by the production method, and the OH group is also contained therein, it is preferable to have a high concentration of OH groups by the above method. .

The concentration of the OH group contained in the cerium oxide particles can be adjusted by changing the temperature and exhaust conditions. The excimer lamp 10 is produced by reheating and slowly cooling to remove the deformation of the discharge vessel 20 and removing the warm exhaust gas for the impure gas contained in the heat release space S. The OH group concentration of the cerium oxide contained in the ultraviolet ray reflecting layer 30 can be adjusted to an arbitrary value by selecting various kinds of such temperature exhausting conditions. Here, the warm exhaust gas refers to a case where a discharge vessel material having a branch pipe capable of being evacuated is connected to an exhaust station, and while the inner space is evacuated from the branch pipe to a vacuum, the electric furnace is kept at a high temperature. For example, the temperature is maintained at 800 ° C, and the holding time is taken as 1 hour, or 5 hours, or 10 hours, or 20 hours, and as the time is longer, more OH groups can be removed. Considering the amount of OH groups previously contained in the cerium oxide particles, by modulating the amount of OH groups removed by warm exhaust gas, ultraviolet reflections of fine particles containing cerium oxide particles having an arbitrary OH group concentration can be formed. Layer 30.

An experimental example of the excimer lamp of the present invention is shown.

<Experimental Example 1>

An excimer lamp having an ultraviolet reflecting layer was produced in accordance with the configuration shown in the first (a) and (b) drawings.

[Basic composition of excimer lamps]

The discharge vessel is made of cerium oxide glass and has a size of 15 mm × 43 mm × 350 mm and a thickness of 2.5 mm.

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

The ultraviolet ray reflection layer is composed of a cerium oxide particle having a center particle diameter of 1.5 μm as a component ratio of 90% by weight, and an alumina particle having a center particle diameter of 1.5 μm as a component ratio of 10% by weight. It was formed, and the firing temperature was 1000 °C.

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

With respect to the excimer lamp having the above configuration, 10 types of lamps 1 to 10 having different temperature and exhaust conditions were prepared. Two pieces of each of the excimer lamps for each condition were produced. One is the reflectance of the ultraviolet ray reflection layer at the initial stage of the measurement, and the OH group concentration in the cerium oxide particles. On the other hand, the tube wall load was set to 0.8 W/cm ² for continuous lighting for 500 hours, and after measuring the illuminance, the reflectance of the ultraviolet ray reflection layer was measured.

The reflectance of the ultraviolet-ray reflective layer is a portion in which an ultraviolet-ray reflective layer is formed on the inner surface of the fracture piece of the discharge vessel, and any three sheets are selected, and the three sheets are used as test pieces. Vacuum ultraviolet light having a wavelength of 172 ± 5 nm was irradiated to three test pieces using a vacuum ultraviolet spectroscopic device, and the reflectance was determined from the intensity ratio of the intensity of the irradiated light to the intensity of the reflected light. The average value of the reflectance of the three test pieces was taken as the reflectance of the ultraviolet reflective layer.

The OH group concentration in the cerium oxide particles is an excimer lamp for measuring the reflectance, and the ultraviolet ray reflection layer is completely cut off from the discharge vessel, and the ultraviolet ray reflection layer which is cut off from the one excimer lamp is divided into three. . The three ultraviolet reflective layers that were cut off were measured by a temperature-rise gas separation method. The average value of the three measurement results was taken as the OH group concentration in the cerium oxide particles.

Here, the principle of measurement of the OH group concentration in the gas analysis method at the temperature rise will be briefly described. When the cerium oxide particles containing an OH group are heated in a high vacuum, a chemical reaction represented by the following formula is produced.

[Chemical 1]

2≡SiOH→H ₂ O(g)+2SiO ₂

In the temperature-exclusive gas analysis, by quantifying the H ₂ O, the weight of the OH group contained in the cerium oxide particles (measured weight) can be determined, and the concentration of the OH group contained in the cerium oxide particles can be determined.

Further, the concentration of the OH group in the cerium oxide particles means that the internal defects are caused by the cerium oxide particles contained in the ultraviolet ray reflecting layer, and thus the OH group for the cerium oxide particles contained in the ultraviolet ray reflecting layer. concentration. The component ratio of the cerium oxide particles contained in the ultraviolet ray reflection layer to be removed was determined, and the weight of the OH group based only on the weight of the cerium oxide particles was calculated from the component ratio.

A method for calculating the concentration of OH groups in the cerium oxide particles will be described by way of an example. The weight of the ultraviolet-ray reflective layer which was cut off was 0.20 g, and when the component ratio of the cerium oxide particles was 90% by weight, the weight of the cerium oxide particles was 0.18 g. In the temperature-rise desorption gas analysis method, as shown in the chemical formula of the formula 1, a molecule of H ₂ O is formed from two OH groups. Therefore, when the amount of H ₂ O released as a result of the measurement is 1.6 × 10 ¹⁸ molecules, the number of OH groups is 3.2 × 10 ¹⁸ molecules. The molecular weight of OH was 17, and thus the weight of the OH group of 3.2 × 10 ¹⁸ molecules was found to be 9.04 × 10 ^-5 g. Since 0.18 g of cerium oxide particles contained OH groups of 9.04 × 10 ^-5 g, the OH group concentration in the cerium oxide particles was calculated to be 502 wtppm.

As shown in Fig. 2, the illuminance measurement is such that the excimer lamp 10 is fixed to the ceramic support table 41 disposed inside the aluminum container 40, and the ultraviolet illuminance is fixed at a position 1 mm from the surface of the excimer lamp 10. In the state where the internal atmosphere of the aluminum container 40 is replaced with nitrogen, the measuring device 42 is discharged by applying an alternating high voltage of 5.0 kV between the electrodes 11 and 12 of the excimer lamp 10 in the state of the excimer lamp 10. A discharge is generated inside the container to measure the illuminance of the x-ray excimer light in the wavelength range of 150 nm to 200 nm emitted through the mesh of the ground electrode 12.

The illuminance after 15 minutes of continuous lighting was used as the initial illuminance, and the illuminance when the continuous lighting was performed for 500 hours was expressed as a relative value with respect to the initial illuminance, and this value was used as the illuminance maintenance ratio. In other words, the "illuminance maintenance rate" is calculated as [(illuminance after 500 hours of lighting) / (illuminance after lighting)] (%).

The excimer lamp after crushing the lamp for 500 hours was prepared and the reflectance of the ultraviolet ray reflection layer was measured in the same manner as described above. The reflectance after 500 hours of lighting for the initial reflectance was used as the reflection maintenance ratio. The "reflection maintenance rate" was calculated as [(reflectance after 500 hours of lighting) / (initial reflectance)] (%).

The measurement results of the lamps 1 to 10 are shown in Table 1.

Fig. 3 is a graph showing the results of the measurement shown in Table 1, in which the horizontal axis is the OH group concentration (wtppm) in the cerium oxide particles, and the vertical axis is the reflection maintaining ratio (%), and the values of the lamps 1 to 10 are indicated. Chart.

In addition, Fig. 4 is a measurement result shown in Table 1, and the OH group concentration (wtppm) in the horizontal axis is used as the cerium oxide particle, and the illuminance maintenance rate (%) is plotted on the vertical axis, and the lamps 1 to 10 are marked. Numerical chart.

Further, in the graphs of FIGS. 3 and 4, the horizontal axis is a single logarithmic graph which is a logarithmic scale.

From the above results, it can be read that the concentration of the OH group in the cerium oxide particles is less than 10 wtppm, and specifically, when the concentration is 5 wtppm or 7 wtppm, the reflection retention ratio and the illuminance maintenance ratio are both about 80% or less, and the lighting is performed for a long time. Excimer lamps have the ability to reduce processing power. On the other hand, when the concentration of the OH group in the cerium oxide particles is 10 wtppm or more, the reflection retention ratio and the illuminance maintenance ratio are both 90% or more, and the processing ability can be maintained even when the excimer lamp is turned on for a long time. As shown in Fig. 3 and Fig. 4, when the OH group concentration is less than 10 wtppm and 10 wtppm or more, the reflection retention ratio and the illuminance maintenance ratio are rapidly increased, and it is considered that the OH group in the cerium oxide particles is determined. When the concentration is 10 wtppm or more, there is a significant difference, and there is an effect that the illuminance at the time of long-time lighting is maintained.

On the one hand, when the concentration of the OH group in the lamp 10, that is, the cerium oxide particles is 658 wtppm, the reflection maintenance ratio is maintained high, but for the illuminance maintenance rate, it is known that OH in the cerium oxide particles with the lamp 9 When the base concentration is 502 wtppm, the phase is greatly reduced. The illuminance maintenance ratio when the OH group concentration in the cerium oxide particles of the lamp 10 is 658 wtppm is maintained at 81%, and the illuminance maintenance ratio when the OH group concentration in the cerium oxide particles of the lamp 2 is 7 wtppm is 79%. The same degree. In other words, the excellent effect of maintaining the illuminance obtained by setting the OH group concentration in the cerium oxide particles to 10 wtppm or more is not exhibited when the OH group concentration is 658 wtppm.

This may be because if the concentration of the OH group in the cerium oxide particles is too high, the oxygen atoms generated by the OH group react with the rare gas atoms, which hinders the formation of the excimer molecules and lowers the illuminance maintenance ratio. When the concentration of the OH group in the cerium oxide particles is too high, it is exposed to the discharge plasma for heating, and when excited by light, the OH group in the cerium oxide particles is released as water (H ₂ O) to the discharge space. The released water (H ₂ O) is decomposed in the discharge plasma, and in the excimer lamp in which xenon (Xe) is enclosed as a discharge gas, a molecule (XeO) in which a deuterium atom is bonded to an oxygen atom is generated, and Green light having a central wavelength of around 550 nm is emitted from the molecule. As described above, when an oxygen atom reacts with a rare gas, formation of an excimer molecule is hindered, and an illuminance maintenance ratio of excimer light emission having a center wavelength of 172 nm is lowered.

In order to achieve the above phenomenon, even if the reflection maintenance ratio of the ultraviolet ray reflection layer can be maintained, the illuminance maintenance rate may be lowered. Therefore, it is suppressed that excessively existing oxygen atoms generated by the OH group are excessively present in the discharge space, and formation of excimer molecules that react with oxygen atoms and rare gas atoms is prevented, and the illuminance maintenance rate of the excimer lamp is suppressed from being lowered. In order to maintain the effect of maintaining the illuminance obtained by setting the OH group concentration in the cerium oxide particles to 10 wtppm or more, it is also known that the OH group concentration of the cerium oxide particles contained in the ultraviolet ray reflecting layer must be 502 wtppm or less.

<Experimental Example 2>

The same measurement as in Experimental Example 1 was carried out for changing the center particle diameter or the composition ratio of the cerium oxide particles and the alumina particles of the constituent material of the ultraviolet ray reflecting layer.

[Basic composition of excimer lamps]

Except for the specifications of Experimental Example 1, the quasi-molecular lamp produced under the same conditions was prepared except that the ceria particles of the constituent material of the ultraviolet-ray reflective layer and the central particle diameter or the composition ratio of the alumina particles were composed of various modifiers.

Light 11

Alumina particles: center particle size 1.5 μm, composition ratio 20% by weight

Cerium oxide particles: center particle size 1.5 μm, composition ratio 80% by weight

Light 12

Alumina particles: center particle size 1.5 μm, composition ratio 30% by weight

Cerium oxide particles: center particle size 1.5 μm, composition ratio 70% by weight

Light 13

Alumina particles: center particle diameter 0.3 μm, composition ratio 10% by weight

Cerium oxide particles: center particle size 0.3 μm, composition ratio 90% by weight

Light 14

Alumina particles: center particle size 3.5 μm, composition ratio 40% by weight

Cerium oxide particles: center particle size 0.3 μm, composition ratio 60% by weight

Light 15

Alumina particles: center particle size 4.0 μm, composition ratio 10% by weight

Cerium oxide particles: center particle size 0.5 μm, composition ratio 90% by weight

With respect to the excimer lamps (lamps 11 to 15) having the above configuration, the OH group concentration, the reflection retention ratio, and the illuminance maintenance ratio in the cerium oxide particles were measured in the same manner as in Experimental Example 1. The measurement results of the lamps 11 to 15 are shown in Table 2.

The ultraviolet ray reflection layer of the lamps 11 to 15 is one in which the OH group concentration in the cerium oxide particles is in the range of 10 wtppm or more and 502 wtppm or less. Moreover, the reflection retention ratio or the illuminance maintenance ratio of these ultraviolet reflective layers was confirmed to be 90% or more. As a result of the above, it is understood that the OH group concentration in the cerium oxide particles constituting the ultraviolet ray reflecting layer is changed by changing the center particle diameter or the component ratio of the cerium oxide particles and the alumina particles of the constituent material of the ultraviolet ray reflecting layer. When it is in the range of 10 wtppm or more and 502 wtppm or less, a sufficiently high reflection maintenance ratio or illuminance maintenance ratio can be maintained.

Although the embodiment of the present invention has been described above, it is not limited to the above excimer lamp, and can be applied to the double tube type excimer lamp 50 as shown in Fig. 5. An ultraviolet reflecting layer 54 is formed on the inner surface of the outer tube 52 of the discharge vessel 51 of the excimer lamp 50 shown in Fig. 5 and the outer surface of the inner tube 53. The outer tube 52 has an inner diameter of 24 mm, the inner tube 53 has an outer diameter of 16 mm, a total length of 350 mm, and a thickness of 1 mm, and both of them are composed of cerium oxide glass. An outer electrode 55 made of a mesh metal is provided on the outer surface of the outer tube 52, and an inner electrode 56 of a plate metal is provided on the outer surface of the inner tube 53.

Further, it is also applicable to the square excimer lamp 60 as shown in Fig. 6. The excimer lamp 60 shown in Fig. 6 is formed by a discharge vessel 61 having a rectangular cross section formed by, for example, cerium oxide glass, and a pair of metal is disposed on the outer surface of the discharge vessel 61 facing each other. The outer electrodes 62 and 63 extend in the tube axis direction of the discharge vessel 61. A helium gas in which a discharge gas is sealed is placed in the discharge vessel 61. The inner surface of the discharge vessel 61 is provided with an ultraviolet reflecting layer 64. Further, on either surface of the outer surface of the discharge vessel 61 where the outer electrodes 62 and 63 are not formed, a light exit window 65 in which the ultraviolet ray reflection layer 64 is not formed is formed. The size of the discharge vessel 61 is 14 x 34 x 150 mm and the thickness is 2.5 mm.

10. . . Excimer lamp

11. . . High voltage supply electrode

12. . . Ground electrode

20. . . Discharge capacitor

twenty one. . . Upper wall

twenty two. . . Lower wall

twenty three. . . Side wall panel

twenty four. . . End wall

30. . . Ultraviolet reflective layer

40. . . Aluminum container

41. . . Support table

42. . . Ultraviolet illuminance tester

S. . . Discharge space

Fig. 1 is a cross-sectional view showing the outline of an example of an excimer lamp of the present invention, and Fig. 1(a) is a cross-sectional view showing a cross section along the longitudinal direction of the discharge vessel, first (b) is a cross-sectional view taken along line A-A' of Fig. 1(a).

Fig. 2 is a cross-sectional view showing a method of measuring the illuminance of the excimer lamp of the experimental example.

Fig. 3 is a graph showing the measurement results of the experimental examples.

Fig. 4 is a graph showing the measurement results of the experimental examples.

Fig. 5 is a schematic explanatory view showing a schematic configuration of an example of the excimer lamp of the present invention.

Fig. 6 is a schematic explanatory view showing a schematic configuration of an example of the excimer lamp of the present invention.

Fig. 7 is a cross-sectional view showing the outline of a configuration of a conventional excimer lamp.

10. . . Excimer lamp

11. . . High voltage supply electrode

12. . . Ground electrode

20. . . Discharge capacitor

twenty one. . . Upper wall

twenty two. . . Lower wall

twenty three. . . Side wall panel

twenty four. . . End wall

30. . . Ultraviolet reflective layer

S. . . Discharge space

Claims (1)

An excimer lamp is a discharge vessel comprising a ceria glass having a discharge space, and a pair of electrodes are provided in a state in which ceria glass forming the discharge vessel is interposed, and a discharge is sealed in the discharge space. An excimer lamp formed of a gas and having an ultraviolet reflecting layer formed on an inner surface of the discharge vessel, wherein the ultraviolet reflecting layer is composed of: cerium oxide particles containing an OH group, and a melting point ratio The cerium oxide particles having a high cerium oxide content are composed of fine particles, and the OH group concentration in the cerium oxide particles constituting the ultraviolet ray reflecting layer is a calculated value for quantifying H 2 O in the temperature-rise desorption gas analysis method, and is 10 wtppm or more and 502 wt ppm or less.