KR20090127215A - Excimer lamp - Google Patents

Abstract

PURPOSE: An excimer lamp is provided to control the extent of the illuminance degradation by including the ultraviolet radiation layer. CONSTITUTION: The discharge vessel(20) is made of the silica glass having the discharge space. The electric discharge gas is sealed in the discharge space(S). In a part of the lower surface of the discharge vessel, the ultraviolet radiation layer is formed. The ultraviolet radiation layer(30) comprises the accumulation structure A formed in one electrode. The ultraviolet radiation layer comprises the accumulation structure B at least formed in a part except the area corresponding to electrode. The accumulation structure A(31) comprises the silica including the OH group and the minute particle of high melting point. The OH group concentration of the silica particle is 10 wtppm or greater.

Description

Excimer lamp {EXCIMER LAMP}

TECHNICAL FIELD The present invention relates to an excimer lamp used for performing a surface treatment such as a washing treatment, an ashing treatment, a film forming treatment, or the like by irradiating ultraviolet rays.

A technique of treating a target object by the action of vacuum ultraviolet light and ozone generated thereby by irradiating a vacuum ultraviolet light having a wavelength of 200 nm or less to a target object such as a glass substrate or a semiconductor wafer of a liquid crystal display device; For example, the cleaning process technique which removes the organic contaminant adhering to the surface of a to-be-processed object, and the oxide film formation process technique which forms an oxide film on the surface of a to-be-processed object are developed and put into practice.

As an apparatus for irradiating vacuum ultraviolet light, for example, an excimer discharge is generated by enclosing a gas for discharge into a discharge container made of a dielectric material, applying an alternating current high voltage through the discharge container, and emitting excimer light emission that is vacuum ultraviolet light. One equipped with an excimer lamp is used. In such excimer lamps, many attempts have been made to efficiently emit higher intensity ultraviolet rays.

Specifically, an ultraviolet reflecting layer is formed on the inner surface of the discharge vessel of the excimer lamp, and the ultraviolet reflecting layer transmits ultraviolet rays, and fine particles such as silica only, or silica and other fine particles such as alumina And a technique formed by laminating magnesium fluoride, calcium fluoride, lithium fluoride, magnesium oxide and the like are disclosed (see Patent Document 1).

In the excimer lamp having such a configuration, ultraviolet rays which do not directly radiate toward the light emitting portion among the ultraviolet rays generated in the discharge vessel are incident on the ultraviolet reflection layer, and refraction and reflection are repeatedly performed on the surfaces of the plurality of fine particles constituting the ultraviolet reflection layer. By diffusing and reflecting by, it radiates from a light output part. Thereby, an ultraviolet-ray can be radiated efficiently.

In lamps that emit ultraviolet rays, for example, silica glass is widely used as a material constituting the discharge vessel. Therefore, as the fine particles constituting the ultraviolet reflecting layer, in order to eliminate the difference in thermal expansion coefficient with the silica glass constituting the discharging vessel, or to make it extremely small to increase the adhesion to the ultraviolet reflecting layer silica glass, It is preferable to comprise so that the silica particle of a material may be included.

The to-be-processed object of surface treatment has many things of the flat shape like the glass substrate of a liquid crystal panel, for example. Therefore, the excimer lamp which consists of a discharge container of the flat shape like a to-be-processed object can reduce the absorption of the ultraviolet-ray by oxygen by reducing the clearance of a light-emitting part and a to-be-processed object, and surface treatment is carried out efficiently. Can be carried out. As an excimer lamp which consists of such a discharge container, for example, patent document 2 discloses the excimer lamp which consists of a square discharge container.

As an excimer lamp which consists of a discharge container with a flat light output part, there exists a structure as shown in FIG. The excimer lamp 10 is composed of a flat rectangular discharge vessel 20 made of silica glass, and the discharge vessel 20 includes an upper wall plate 21 and a lower wall plate 22. And the side wall plate 23 and the end wall plate 24 are connected, and the gas for discharge is enclosed inside. In addition, the outer surface of the upper wall plate 21 is provided with a high voltage supply electrode 11 and the ground electrode 12 on the outer surface of the lower wall plate 22, and these electrodes 11 and 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 serving as the light exit portion.

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

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

However, in the excimer lamp provided with the ultraviolet reflecting layer which consists of microparticles containing a silica particle, when illuminating for a long time, illuminance retention will gradually fall gradually. For this reason, for example, in the case of performing surface treatment such as washing treatment, there is a problem that the processing capability of the excimer lamp changes depending on the lighting time even when the treatment is to be performed with a constant illuminance.

This invention is made | formed based on the above circumstances, Even if it is equipped with the ultraviolet reflecting layer which consists of microparticles containing a silica particle, and lighting it for a long time, the degree of illumination intensity fall is suppressed small and a vacuum ultraviolet light is emitted efficiently. It is an object of the present invention to provide an excimer lamp.

The excimer lamp of the first invention of the present application is provided with a discharge container made of silica glass having a discharge space, and a pair of electrodes are provided in a state where the silica glass forming the discharge container is interposed, and the discharge gas is discharged in the discharge space. Is an excimer lamp in which an ultraviolet reflecting layer is formed on a part of the inner surface of the discharge container, wherein the ultraviolet reflecting layer is formed of at least a portion of the deposit A formed in at least a part of the region corresponding to one electrode and the region corresponding to the electrode. Composed of at least a portion of deposit B formed, the deposit A is composed of silica particles containing OH groups and fine particles having a higher melting point than silica,

The deposit B is composed of fine particles containing silica particles containing OH groups, and the concentration of OH groups in the silica particles constituting the ultraviolet reflection layer is 10 wtppm or more.

Further, in the first invention of the present application, in the first invention of the present application, the installation area of the deposit body A is a (cm 2), the installation area of the deposit B is b (cm 2), and the specific surface area of the deposit B is c (cm 2). / g), when the inner surface area of the discharge vessel is d (cm 2),

^{b≥-5.0 × 10 -7 ac +} 0.35a, also, b> 0.02d

Characterized by satisfying.

By incorporating fine particles having a melting point higher than that of silica into the ultraviolet reflecting layer, it is possible to prevent the grain boundaries from adhering to each other adjacent to each other and to lose the grain boundary, and to suppress the decrease in the reflectance of the ultraviolet reflecting layer. In particular, since the deposit A formed in the area | region corresponding to an electrode is easy to receive the heat of a plasma, it is necessary to mix microparticles with a melting point higher than silica, and to suppress the fall of the reflectance of an ultraviolet reflecting layer.

In addition, the inclusion of OH groups in the silica particles constituting the ultraviolet reflecting layer suppresses the generation of internal defects in the silica particles included in the ultraviolet reflecting layer, prevents the absorption of light of the wavelength in the ultraviolet region by the ultraviolet reflecting layer, and reflectance of the ultraviolet reflecting layer. , The degree of decrease in illuminance of the excimer lamp can be suppressed to be small, and the vacuum ultraviolet light can be efficiently emitted. In particular, when the concentration of OH groups in the silica particles constituting the ultraviolet reflecting layer is 10 wtppm or more, the reflection retention rate and illuminance retention rate can be maintained high, and the effect of remarkably excellent illuminance retention when turned on for a long time is exerted.

The ultraviolet reflecting layer formed on the inner surface of the discharge vessel corresponding to the position where the electrode is provided is exposed to the discharge plasma when OH group is contained, and emits an impure gas containing water as a main component. When impurity gas containing water as a main component is combined with the gas for discharge, the illuminance of excimer light emission falls. However, by forming an ultraviolet reflecting layer on a part of the inner surface of the discharge vessel corresponding to the position where the electrode is not provided, the ultraviolet reflecting layer adsorbs the water released and simultaneously the oxygen generated by the decomposition of water in the plasma, thereby excimer light emission. Can reduce the roughness of the. Therefore, even when the excimer lamp is turned on for a long time, the degree of illuminance decrease can be suppressed small and the vacuum ultraviolet light can be emitted efficiently.

Considering the specific surface area of the deposit B, the installation area of the deposit A is a (cm 2), the installation area of the deposit B is b (cm 2), the specific surface area of the deposit B is c (cm 2 / g), the discharge vessel When the inner surface area of is d (㎠),

^{b≥-5.0 × 10 -7 ac +} 0.35a, also, b> 0.02d

By satisfying this, it is possible to prevent the impurity gas from remaining in the discharge space without the amount of impurity gas emitted from the deposit A exceeding the amount of the impurity gas that the deposit B can adsorb. Therefore, it is possible to suppress the lowering of illuminance of excimer light emission by combining oxygen atoms contained in the impurity gas with the gas for discharge, and even when the excimer lamp is turned on for a long time, the lowering of illuminance can be suppressed and the vacuum ultraviolet light can be efficiently You can exit.

1 is a cross-sectional view illustrating the outline of a configuration in an example of an excimer lamp 10 of the present invention. (a) is sectional drawing which shows the cross section along the longitudinal direction of the discharge container 20, (b) is sectional drawing of the line A-A 'in (a).

This excimer lamp 10 is provided with the hollow elongate discharge container 20 of cross-sectional square shape in which the both ends were hermetically sealed and the discharge space S was formed inside. The discharge vessel 20 includes a pair of side wall plates 23 connected to the lower wall plate 22 and the upper wall plate 21 and the lower wall plate 22 that face the upper wall plate 21 and the upper wall plate 21. And a pair of end wall plates 24 provided to seal both ends of the rectangular cylindrical body formed of these upper wall plates 21, lower wall plates 22, and a pair of side wall plates 23. The discharge vessel 20 is formed of silica glass, for example, synthetic quartz glass, which transmits vacuum ultraviolet light well.

The gas for discharge is enclosed in the discharge container 20 by the pressure of 10-80 kPa, for example. Although any gas selected as the gas for discharge does not affect the continuous change in the emission intensity, the center wavelength of excimer light emitted is different depending on the type of discharge gas. For example, excimer light emission with a center wavelength of 172 nm occurs in an excimer lamp containing xenon (Xe), and 175 nm of a excimer lamp containing a mixed gas of argon (Ar) and chlorine (Cl) as a center wavelength. Excimer light emission occurs, and in the excimer lamp in which a mixed gas of krypton (Kr) and oxo (I) is enclosed, excimer light emission with a center wavelength of 191 nm occurs, and a mixed gas of argon (Ar) and fluorine (F) Excimer light emission with a wavelength of 193 nm is generated in the encapsulated excimer lamp, and excimer light emission with a wavelength of 207 nm occurs in an excimer lamp in which a mixed gas of krypton (Kr) and cancellation (Br) is enclosed. In the excimer lamp in which the mixed gas of krypton (Kr) and chlorine (Cl) is enclosed, the excimer light emission with a center wavelength of 222 nm occurs, and in the excimer lamp in which the mixed gas of xenon (Xe) and chlorine (Cl) is enclosed Excimer light emission with a center wavelength of 308 nm occurs.

The outer surface of the upper wall plate 21 in the discharge vessel 20 may be provided with the high voltage supply electrode 11 and the ground electrode 12 on the outer surface of the lower wall plate 22, and these electrodes 11 and 12. Are arranged to face each other. These electrodes 11 and 12 have a network structure and are formed to transmit light from between the meshes. As a material, aluminum, nickel, gold, etc. are used, for example, and are formed by means of screen printing or vacuum deposition, for example. In addition, each of the electrodes 11 and 12 is connected to a suitable high frequency power supply (not shown).

In the excimer lamp 10, in order to use the vacuum ultraviolet light generated by the excimer discharge with good efficiency, the ultraviolet reflecting layer 30 made of fine particles on the inner surface facing the discharge space S of the discharge vessel 20. Is installed. The ultraviolet reflecting layer 30 is composed of the deposit A 31 and the deposit B 32. The deposit A 31 is a part of the inner surface facing the discharge space S of the discharge vessel 20 in which the high voltage supply electrode 11 is installed, that is, the high voltage supply electrode on the inner surface of the upper wall plate 21 ( It is formed in part of the area corresponding to 11). The deposit B 32 is a part of the inner surface facing the discharge space S of the discharge vessel 20 in which the high voltage supply electrode 11 or the ground electrode 12 is not provided, that is, the electrodes 11 and 12. The inner surface of the upper wall plate 21 and the lower wall plate 22 and the inner surface of the side wall plate 23 and the end wall plate 24 which are out of the area | region corresponding to (circle) are formed. That is, the ultraviolet reflecting layer 30 formed in the area | region corresponding to the high voltage supply electrode 11 of the inner surface of the upper wall plate 21 is called the deposit body A31, and the surface of the inner surface of the discharge container 20 is called The ultraviolet reflecting layer 30 formed in the outer region is called the deposit B 32.

On the other hand, since the ultraviolet reflecting layer 30 is not formed in the inner surface corresponding to the ground electrode 12 of the lower wall plate 22 in the discharge vessel 20, the light output part is comprised.

The deposit A 31 has a thickness of, for example, 5 to 1000 µm, and is composed of silica particles and fine particles having a higher melting point than silica and transmitting ultraviolet rays. The fine particles having higher melting point than silica and transmitting ultraviolet rays are, for example, alumina, lithium fluoride, magnesium fluoride, calcium fluoride, barium fluoride and the like.

When vacuum ultraviolet light enters such a deposit A 31, part of it is reflected at the surface of the microparticles, and part of it is refracted to transmit to the inside of the particle, and then reflected or refracted at another surface. By repeating such reflection and refraction in a plurality of fine particles, 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 are lost, and the vacuum ultraviolet light cannot be diffusely reflected and the reflectance sometimes decreases. In particular, the deposit A 31 formed in the region corresponding to the high voltage supply electrode 11 is susceptible to the heat of plasma, and the silica particles constituting the deposit A 31 are easy to melt. On the other hand, fine particles having a higher melting point than silica do not melt even when exposed to heat by plasma. Therefore, by incorporating the fine particles having a melting point higher than that of silica into the deposit body A31, the particles adjacent to each other are bonded to each other to prevent loss of grain boundaries and the reduction of the reflectance of the deposit body A31 can be suppressed. have.

The deposit B 32 is 10-1000 micrometers in thickness, for example, and is comprised from the microparticles containing a silica particle. The microparticles constituting the deposit B 32 may be formed of a mixture of insulating microparticles containing a substance which combines with oxygen and a substance which transmits ultraviolet rays, even though it is composed of only silica particles. For example, alumina, lithium fluoride, magnesium fluoride, calcium fluoride and barium fluoride may be used.

Even when vacuum ultraviolet light enters the deposit B 32, the vacuum ultraviolet light is diffusely reflected by reflection and refraction repeatedly occur in a plurality of fine particles. Moreover, since the deposit B 32 is formed in the inner surface of the discharge container 20 other than the area | region corresponding to the electrodes 11 and 12, it is hard to be influenced by the heat by a plasma. Therefore, even if the deposit body B 32 is comprised only from silica particles, the loss of the grain boundary due to the bonding of adjacent microparticles hardly occurs.

The fine particles have a particle diameter defined as follows, for example, in the range of 0.01 to 20 µm, and the central particle size (maximum value of the particle size distribution on the basis of the number) is, for example, in the deposit A 31. For example, it is preferable that it is 0.1-10 micrometers, More preferably, it is 0.1-3 micrometers, and it is preferable that it is 0.1-20 micrometers similarly in the deposit body B similarly.

Here, the "particle diameter" referred to is a scanning electron microscope (SEM) using approximately its intermediate position in the thickness direction at the fracture surface when fractured in the vertical direction with respect to the surface of the ultraviolet reflective layer 30. An enlarged projected image is obtained, and the Feret diameter which is an interval of the said parallel line when the arbitrary particle | grains in this enlarged projected image are sandwiched between two parallel lines of a fixed direction is called.

In addition, a "central particle diameter" means the range of the particle diameter of the maximum value and the minimum value with respect to the particle diameter of each particle obtained as mentioned above in the range of 0.1 micrometer, for example, 15 division into several divisions, for example, 15 divisions. It divides to the extent and says the center value of the division in which the number (the frequency) of particle which belongs to each division becomes maximum.

In this excimer lamp 10, when lighting power is supplied to the high voltage supply electrode 12, excimer discharge is generated in the discharge space S between the positive electrodes 11 and 12 via the discharge vessel 20. As a result, excimer molecules are formed, and vacuum ultraviolet light is emitted from the excimer molecules. A part of the vacuum ultraviolet light generated in the discharge space S is directly emitted to the outside through the lower wall plate 22 serving as the light emitting portion. In addition, some of the vacuum ultraviolet light is radiated in the direction of the upper wall plate 21, but is diffusely reflected by the ultraviolet reflecting layer 30, and is emitted to the outside through the light output unit.

The fine particles constituting the ultraviolet reflecting layer 30 have a particle diameter the same as the wavelength of the vacuum ultraviolet light, so that the vacuum ultraviolet light can be efficiently diffusely reflected.

However, when the excimer lamp 10 including the ultraviolet reflective layer 30 is turned on for a long time, the initial illuminance cannot be maintained and the illuminance gradually decreases with the lighting time. The inventors examined the cause of the lowering of the illuminance from all aspects, and considered that the reflectance of the ultraviolet reflecting layer 30, which is one of the factors, may be reduced.

Therefore, the reflection intensity spectrum of the ultraviolet reflection layer 30 of the excimer lamp 10 of lighting initial stage and the reflection intensity spectrum of the ultraviolet reflection layer 30 of the excimer lamp 10 after long-time lighting were measured, and both were compared and analyzed. From this result, it was found that in the ultraviolet reflecting layer 30 of the excimer lamp 10 after the long-time lighting, an absorption band was generated in the ultraviolet region, and a decrease in the illuminance occurred when a part of the ultraviolet light was absorbed by the ultraviolet reflecting layer 30.

The absorption band in the ultraviolet region generated in the ultraviolet reflecting layer 30 is subjected to radiation damage by the silica particles constituting the ultraviolet reflecting layer 30 being exposed to ultraviolet rays or plasma during discharge, thereby receiving light having a wavelength in the ultraviolet region. It is thought that the internal defect to absorb arises, and a diffuse reflection is suppressed by an ultraviolet-ray absorbed by an internal defect. An internal defect is Si-Si defect which has an absorption edge near wavelength 163 nm which arises when the Si-O-Si bond of a silica particle is exposed to ultraviolet-ray or a plasma, or E'center which has an absorption band near wavelength 215 nm. (Si ·).

For the same reason as above, it is considered that an internal defect that absorbs light of a wavelength in an ultraviolet region is generated by silica particles, and absorption of light of a wavelength in an ultraviolet region that causes a decrease in illuminance is considered to depend on an internal defect of silica particles. Moreover, radiation damage does not occur in microparticles which permeate ultraviolet rays other than silica particles which consist of alumina, lithium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, etc., even if exposed to an ultraviolet-ray or a plasma. Therefore, by preventing the internal defects from occurring in the silica particles constituting the ultraviolet reflecting layer 30, it is considered that the lowering of the illuminance can be suppressed and the high illuminance retention can be maintained even if it is turned on for a long time.

In order to prevent an internal defect from generating in a silica particle, it is effective to contain an OH group in a silica particle. By containing an OH group, it can suppress that internal defects generate | occur | produce in the silica particle contained in the ultraviolet reflecting layer 30, and the fall of the reflectance of the ultraviolet reflecting layer 30 can be prevented.

Next, the formation method of the ultraviolet reflecting layer 30 which consists of microparticles containing the silica particle containing an OH group is demonstrated. As for the ultraviolet reflecting layer 30, the particle | grain deposition layer containing a silica particle is formed in the predetermined | prescribed area | region in the inner surface of a discharge container formation material by the method called "flow method." For example, microparticles are mixed and the dispersion liquid is adjusted to the solvent which has a viscosity which combined water and PEO resin (polyethylene oxide: polyethylene oxide), and this dispersion liquid is poured into a discharge container formation material. Then, the dispersion is attached to a predetermined region on the inner surface of the discharge vessel forming material, followed by drying and firing to evaporate water and the PEO resin, whereby a particle deposition layer can be formed. Here, baking temperature becomes 500 degreeC-1100 degreeC, for example.

As an example of a method in which OH groups are contained in the silica particles, silica particles containing a large amount of OH groups may be produced by heating the silica particles not containing OH groups with electricity (eg, 1000 ° C.) while supplying water vapor. By using the silica particle which carried out such a process, the ultraviolet-ray reflection layer 30 which consists of microparticles containing the silica particle containing an OH group can be formed.

As another method, silica particles containing no OH group may be used to adhere to a predetermined region on the inner surface of the discharge vessel forming material and then fired while supplying water vapor, whereby the silica particles may contain OH groups. In addition, after firing using silica particles not containing OH groups to form the ultraviolet reflecting layer 30, the OH groups can be included in the silica particles by heating with electricity while supplying steam again.

In addition, although the silica particle which can be obtained by purchasing may contain the product containing OH group by the manufacturing method, there exist some products with low OH group concentration in it, It is preferable to contain a high concentration of OH group once by the said method. Do.

The density | concentration of the OH group contained in a silica particle can adjust the OH group concentration contained in the silica particle which comprises the ultraviolet-ray reflection layer 30 to arbitrary values by selecting various warm-exhaust conditions. For example, even if the holding temperature is constant, as the holding time is lengthened, more OH groups can be removed. Considering the amount of OH groups previously included in the silica particles, and preparing the amount of OH groups to be removed by the warm exhaust, the ultraviolet reflecting layer 30 made of fine particles containing silica particles of any OH group concentration is formed. can do.

The first experiment on the excimer lamp is shown.

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

[Basic structure of excimer lamp]

The discharge vessel is made of silica glass, and the dimension is 15 mm x 43 mm x 350 mm in thickness of 2.5 mm.

The dimensions of the high voltage supply electrode and the ground electrode are 30 mm x 300 mm.

The ultraviolet reflecting layer is composed of a mixture of silica particles having a particle diameter of 1.5 μm and alumina particles having a component diameter of 90 μm and a component ratio of 10% by weight of a component having a central particle diameter of 1.5 μm, respectively. did.

Xenon was sealed at 40 kPa in a discharge vessel as a gas for discharge.

About the excimer lamp which has the said structure, OH group concentration in a silica particle, reflection retention, and roughness retention were measured. The ultraviolet-ray reflection layer was scraped off from a discharge container, and it measured using the temperature-exit gas analysis method, and calculated the OH group concentration in the silica particle contained in an ultraviolet-ray reflection layer. Moreover, the component ratio of the silica particle contained in the ultraviolet-ray reflection layer cut out was calculated | required, and the weight of the OH group with respect to the weight of a silica particle only was computed and calculated from the component ratio. Moreover, the reflection retention and illumination intensity retention of the ultraviolet-ray reflection layer after 500 hours of continuous lighting about the initial state were measured using the vacuum ultraviolet light spectroscopy apparatus (VUV) or an ultraviolet illuminometer.

The measurement results of lamps 1 to 5 are shown in Table 1.

TABLE 1

FIG. 2: is a graph which plotted the values of lamps 1-5 with OH group concentration (wtppm) in a silica particle on the horizontal axis, and reflection retention (%) on the vertical axis | shaft with respect to the measurement result shown in Table 1. FIG.

3 is a graph which plotted the values of lamps 1-5 with OH group concentration (wtppm) in a silica particle on the horizontal axis, and roughness retention (%) on the vertical axis | shaft with respect to the measurement result shown in Table 1. FIG.

In addition, the graph shown to FIG. 2 and FIG. 3 is the one logarithmic graph whose horizontal axis is a logarithmic scale.

From the above results, when the OH group concentration in the silica particles is less than 10 wtppm, the reflection retention ratio and the roughness retention ratio remain low, and it can be read that 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, the reflection retention rate and the roughness retention rate are 90% or more, and it can be read that the processing capacity can be maintained even if the excimer lamp is turned on for a long time. As shown in Fig. 2 and Fig. 3, when the OH group concentration becomes 10 wtppm or more from less than 10 wtppm, the reflection retention rate and the roughness retention rate increase rapidly, so that a remarkable difference is recognized when the OH group concentration in the silica particles is 10 wtppm or more. It has been found that the effect of maintaining the illuminance when lighting for a long time is quite excellent.

However, even when the OH group concentration in the silica particles constituting the ultraviolet reflecting layer 30 is 10 wtppm or more, the illuminance of excimer light emission having 172 nm of the excimer lamp as the center wavelength has occurred. In addition, during the lighting of the excimer lamp 10 in which xenon is sealed as a gas for discharge, the color of the discharge generated in the discharge space S sometimes becomes green, and a molecule (XeO) in which a xenon atom and an oxygen atom are bonded is generated. From the results, it was confirmed that green light having a center wavelength of around 550 nm was emitted.

In addition, when exposed to the discharge plasma generated in the discharge space, the OH group contained in the silica particles constituting the ultraviolet reflecting layer 30 is heated to emit an impurity gas containing water (H20) as a main component in the discharge space S. It is thought to be. Oxygen atoms generated by the decomposition of the impurity gas containing water as a main component in the plasma are released into the discharge space S from the OH group contained in the silica particles constituting the ultraviolet reflecting layer 30.

In the case where the ultraviolet reflecting layer 30 made of microparticles is formed on the inner surface of the discharge vessel 20, there are irregularities of the microparticles, so that the flat discharge vessel 20 without the ultraviolet reflecting layer 30 is formed. The surface area is larger than the surface. Since the impurity gas is emitted from the ultraviolet reflection layer 30 exposed to the discharge plasma, more impurity gas is generated when the ultraviolet reflection layer 30 is formed. In addition, the microparticles constituting the ultraviolet reflecting layer 30 have a small volume of one particle and have a smaller heat capacity than the discharge vessel 20. For this reason, even if heated in a short time of about 10 ns which discharge plasma generate | occur | produces, it becomes high temperature and it is easy to discharge impurity gas.

Since the deposit A 31 is formed in the area | region corresponding to the high voltage supply electrode 11 of the inner surface of the upper wall board 21, since it is directly exposed to the discharge plasma which generate | occur | produces between the electrodes 11 and 12, it heats. As a result, the impure gas is discharged into the discharge space S. FIG.

On the other hand, the deposit B 32 is an inner surface of the upper wall plate 21 deviating from the high voltage supply electrode 11 or the lower wall plate 22 deviating from the ground electrode 12, or the side wall plate 23 or a single wall plate. Since it is formed in any region of the inner surface of (24), it faces the discharge space S, but is not directly exposed to the discharge plasma which generate | occur | produces between the electrodes 11 and 12. FIG. For this reason, it is considered that almost no impurity gas is generated from the deposit B 32. In contrast, deposit B 32 is considered to adsorb impurity gas and he is demonstrated by the following experiment.

As a 2nd experiment object, the excimer lamp which forms only the deposit B and does not form the deposit A in the inner surface of the discharge container 20 was produced. When encapsulating the gas for discharge using xenon as a gas for discharge, oxygen was also mixed and the excimer lamp which oxygen was previously sealed as an impurity gas was made into the experiment object. The oxygen concentration enclosed in the discharge space S was 160 wtppm, and the pressure of the gas for discharge was 40 kPa. When oxygen is mixed as the impurity gas, it is easy to determine that oxygen is mixed in the discharge space S by reacting with the rare gas and having a large effect on the lowering of illuminance and generating light of a discharge having a wavelength of 550 nm.

Three kinds of excimer lamps were provided on the inner surface of the discharge vessel provided with the deposit B having different component ratios of the particles constituting the fine particles. The lamp 1 is provided with the deposit B which consists only of a silica particle, the lamp 2 is provided with the deposit B which consists of a silica particle and an alumina particle, and the lamp 3 is the deposit body which consists of a silica particle and calcium fluoride particle. B is provided. Moreover, the lamp 4 in which the deposit body B was not formed was prepared as a comparative example. About each lamp, the light emission intensity of 550 nm 15 minutes after continuous lighting until the excimer discharge was stabilized was measured, and it was called "550 nm light emission intensity lighting initial stage." Then, lighting of an excimer lamp was continued, 550 nm light emission intensity after 5 hours of continuous lighting was measured, and it was called "5 hours after 550 nm light emission intensity lighting."

TABLE 2

Table 2 shows the results of the second experiment. The value of "5 hours after 550 nm light emission intensity lighting" is represented by the relative value when the value of "550 nm light emission intensity lighting initial stage" is set to 100. In the lamps 1 to 3 provided with the deposit B, the value after 5 hours of 550 nm emission intensity lighting decreased to 100 or less, and compared with the initial stage of lighting, the molecules (XeO) in which xenon atoms and oxygen atoms were bonded The number decreased. That is, oxygen previously mixed in the discharge space is reduced. On the other hand, in the lamp 4 in which the deposit body B is not formed, it turns out that the value after 5 hours of 550 nm light emission intensity lighting is maintained at 100, and there is no change in the quantity of oxygen previously mixed in the discharge space. Thereby, by providing the deposit B on the inner surface of the discharge vessel of the excimer lamp, it is confirmed that the light of 550 nm is reduced, and it is understood that oxygen is adsorbed on the deposit B. FIG. In addition, since the deposit B is not exposed to the discharge plasma, it is considered that the adsorbed impurity gas is not discharged to the discharge space.

Next, the third experiment was conducted to confirm whether or not the phenomenon in which the oxygen confirmed in the second experiment was adsorbed onto the deposit B was caused by the lighting of the excimer lamp. The lamps 5-7 which have the same structure as the lamps 1-3 which are 2nd experiment objects were made into 3rd experiment objects. Moreover, the lamp 8 in which the deposit body B was not formed was prepared as a comparative example. About each lamp, the light emission intensity of 550 nm after 15 minutes of continuous electric lights was measured, and it was called "550mn light emission intensity lighting initial stage." Thereafter, the sample was left to stand for 48 hours without being lit, and the lamp was turned on after standing, and the light emission intensity at 550 nm after 15 minutes of continuous lighting was measured, and it was referred to as "after 550 nm light emission intensity after 48 hours." Then, lighting of an excimer lamp was continued, 550 nm light emission intensity after 5 hours of continuous lighting was measured, and it was called "after 5 hours of lighting after 48 hours of 550 nm light emission intensity."

TABLE 3

Table 3 shows the results of the third experiment. The value of "after 48 hours of 550 nm emission intensity illumination" and "after 5 hours of lighting after 48 hours of 550 nm emission intensity illumination" is represented by the relative value when the value of "550 nm emission intensity illumination initial stage" is set to 100. Lose. In the lamps 5 to 7 provided with the deposit B, the value after 48 hours of 550 nm light emission intensity is 100, whereas the value after 5 hours of lighting after 48 hours 550 nm light emission intensity decreases to 10-11. It turns out that oxygen is reduced only by turning on an excimer lamp. As a principle that oxygen adsorbs on the deposit B, it is thought that the chemisorption which oxygen adsorbs by adsorb | sucking by the ultraviolet-ray generate | occur | produced by lighting on the surface of the microparticles of the deposit B generate | occur | produces.

On the other hand, in the lamp 8 in which the deposit body B is not formed, the value remains 100 even after 48 hours of 550 nm light emission intensity even after 48 hours of 550 nm light emission intensity. It turns out that there is no change in the amount of oxygen mixed.

Since the fine particles constituting the deposit B adsorb impurity gas on the surface exposed to the discharge space, the larger the surface area facing the discharge space can adsorb more impurity gas. Therefore, the larger the "specific surface area", that is, the total sum of the surface areas of all the particles contained in the unit weight of powder, the more the impure gas is adsorbed. A specific surface area is measured using the measuring method called BET method which adsorb | sucks molecular gas (for example, nitrogen) which occupies a known area on a surface of microparticles previously, and calculates a specific surface area from the quantity. . When the specific surface area of the microparticles constituting the deposit B is measured, the surface exposed to the discharge space of the deposit B is exposed to molecular gas and adsorbed, and the specific surface area is obtained from the amount.

Below, the 4th experiment performed in order to confirm the effect of this invention is shown.

<Experimental object>

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

[Basic structure of excimer lamp]

The discharge vessel is made of silica glass, having dimensions of 15 mm x 43 mm x 540 mm and thickness of 2.5 mm.

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

The dimension of the light output portion corresponding to the region where the deposit B was not formed in the lower wall plate was 2 mm larger than the ground electrode and 36 mm x 504 mm.

Deposit A and deposit B were each formed by the falling method, and the baking temperature was 1000 degreeC.

After carrying out the warming and exhausting under conditions of 800 ° C. for 1 hour (time after temperature rise), xenon was encapsulated in a discharge vessel. The encapsulation amount is 40k㎩.

The OH group content of the deposit A of the produced lamp is 500 wtppm.

As shown in Table 4, four types of the structure (1-1), the structure (1-2), the structure (1-3), and the structure (1-4) were prepared about the structure of the deposit A. FIG. Each of the four types of structures is common for the material, particle diameter, center particle size, and component ratio, but the installation area of the deposit A formed in the region corresponding to the high voltage supply electrode on the inner surface of the upper wall plate is 160 cm 2, 128 cm 2, 107 cm 2 and 40 cm 2. Since the amount of impurity gas discharged into the discharge space depends on the installation area of the deposit body A, as in the configuration (1-1), the larger the installation area of the deposit body A is, the larger the amount of impurity gas is. As described above, the smaller the installation area of the deposit A is, the less the amount of impurity gas is. Moreover, in the structure (1-2), the structure (1-3), and the structure (1-4), since the installation area in which the deposit body A is formed is smaller than the area in which the high voltage supply electrode is formed, 160 cm <2>, The deposit A is formed not in all the regions of the inner surface of the discharge vessel provided with the high voltage supply electrode.

TABLE 4

Moreover, as shown in Table 5, also about the structure of the deposit body B, four types of the structure (2-1), the structure (2-2), the structure (2-3), and the structure (2-4) were prepared. . The structure (2-1), the structure (2-2), and the structure (2-3) consist only of a silica particle, and the structure (2-4) consists of a silica particle and an alumina particle. The structure (2-1), the structure (2-2), and the structure (2-3) have a specific surface area of 16 × 10 ⁴ cm 2 / g, 4 × 10 ⁴ cm 2 / g, by changing the particle diameter of the silica particles. 1 x 10 ⁴ cm 2 / g. In addition, the specific surface area of the structure (2-4) is 4 * 10 <^4> cm <2> / g. Since the larger the specific surface area of the deposit B, the more impurities are adsorbed. Since the larger the specific surface area of the deposit B, the larger the surface area faces in the discharge space as in the configuration (2-1), the amount of impurity gas incorporated into the discharge space. This lighting decreases, and the smaller the specific surface area of the deposit B as in the configuration (2-3), the smaller the amount decreasing with lighting of the impure gas mixed in all the spaces.

TABLE 5

About the thing which made sediment A into structure (1-1), the thing which made sediment B into structure (2-1)-structure (2-4) prepared for the experiment. Moreover, about each combination, five kinds of things which changed the installation area of the deposit B were prepared. Similarly, what set deposit B into structure (2-1)-structure (2-3) about what set deposit A into structure (1-2), structure (1-3), structure (1-4) Prepared.

About each excimer lamp comprised in this way, it is made to light on the conditions which the pipe wall load of a discharge container becomes 0.6 W / cm <2>, and illuminance of the xenon excimer light of the wavelength range of 150 nm-200 nm of wavelength 15 minutes after continuous lighting. And illuminance of the xenon excimer light in the wavelength range of 150 nm to 200 nm after continuous lighting for 500 hours under constant tube wall load. The illuminance after 15 minutes of continuous lighting is the initial illuminance, and the illuminance after illuminating the light continuously for 500 hours is the relative value of the initial illuminance as the illuminance retention rate. Roughness)] (%). The reason for 500 hours is as follows. Since the decrease in illuminance caused by the impurity gas continues for up to 500 hours, the illuminance thereafter does not decrease, because all of the impurity gas contained in the ultraviolet reflecting layer is released for up to 500 hours and is not released thereafter. to be.

Since roughness maintenance of 80% or more may be required as a standard of the product, when the roughness maintenance ratio becomes 80% or more for 500 hours as a judgment, the time when the roughness maintenance ratio becomes 80% or less for 500 hours is determined as "x." I did it.

As shown in FIG. 4, the illuminance measurement is fixed from the surface of the excimer lamp 10 while fixing the excimer lamp 10 on the support 41 made of ceramic disposed inside the aluminum container 40. In the position away from the mm, the ultraviolet illuminometer 42 is fixed so as to face the excimer lamp 10, and in the state where the internal atmosphere of the aluminum container 40 is replaced with nitrogen, the electrodes 11, By applying an alternating current high voltage of 5.0 kV between 12), a discharge was generated inside the discharge vessel 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 this result, in each combination of the structure of the deposit A and the structure of the deposit B, the combination which extracted the smallest installation area of the deposit B was extracted among the excimer lamps with which illumination intensity retention becomes 80% or more for 500 hours. For example, the lamp 3 corresponds to a combination in which the structure of the deposit A is "constitution (1-1)" and the structure of the deposit B is "constitution (2-1)." Similarly, the lamp 8, the lamp 13, the lamp 18, and the like correspond.

In this way, Table 6 shows the structure of the deposit A, the structure of the deposit B, the specific surface area of the deposit B, and the installation area of the deposit B.

TABLE 6

7 is a graph showing the results in Table 6. FIG. The horizontal axis was made the specific surface area (* 10 <^4> cm <2> / g) of the deposit body B, the vertical axis was made the installation area (cm <2>) of the deposit body B, and the value was plotted for every structure of the deposit A. FIG.

Table 6 and FIG. 7 show that the larger the specific surface area, the smaller the installation area required for suppressing roughness reduction. For each structure of the deposit A, that is, the structure (1-1), the structure (1-2), and the structure (1-3), the installation area is proportional to the specific surface area, respectively. However, in the excimer lamp which has the structure (1-4) as the deposit body A, even if a specific surface area increases, the installation area did not become a value lower than 10 cm <2>.

In the excimer lamp having the constitution (1-4) as the deposit body A, since the installation area of the deposit body B is too small with respect to the internal volume of the discharge vessel, the probability that the impurity gas diffused in the discharge space reaches the deposit body B is reached. It is thought that this is because it is lowered and the effect of adsorption does not appear. That is, it can be said that it is the area of the deposit B which minimum requires the magnitude | size of discharge space. When 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 approximately 500 cm 2, whereas the installation area of the deposit B is 10 cm 2. Therefore, the minimum required installation area of the deposit B is 0.02 times the inner surface area of the discharge vessel.

Next, the respective inclinations and intercepts of the approximate straight lines of each structure of the deposit A in FIG. 7, that is, the structure (1-1), the structure (1-2), and the structure (1-3) are derived. did. Table 7 shows the intercepts of the composition of the deposit A, the installation area of the deposit A, the slope of the relationship between the specific surface area and the installation area of the deposit B, and the relationship between the specific surface area and the installation area of the deposit B. Shown in

TABLE 7

Fig. 8 shows the results of Table 7 in which the abscissa represents the installation area (cm 2) of the deposit A, and the ordinate represents the slope (× 10 ⁻⁴ g) of the relationship between the specific surface area of the deposit B and the installation area. Plotted.

From the graph, it can be seen that the slope of the relationship between the specific surface area of the deposit B and the installation area is in a proportional relationship having a negative slope with respect to the installation area (cm 2) of the deposit A. FIG. When setting the installation area of the deposit A as a (cm <2>), the inclination of the relationship between the specific surface area and the installation area of the deposit B can be represented by -5.0x10 <^-7> a.

FIG. 9 plots the values as the intercepts (cm 2) of the relationship between the specific surface area and the installation area of the deposit B, with the abscissa being the installation area (cm 2) of the deposit A.

In the graph, it can be seen that the intercept of the relationship between the specific surface area of the deposit B and the installation area is in a proportional relationship having a positive slope with respect to the installation area (cm 2) of the deposit A. FIG. When setting the installation area of the deposit A as a (cm <2>), the intercept of the relationship of the specific surface area and the installation area of the deposit B can be represented by 0.35xa.

In addition, in FIG. 7, the installation area of the deposit B is "the slope of the relationship between the specific surface area of the deposit B and the installation area" with respect to the specific surface area of the deposit B, and the "specific surface area and installation area of the deposit B" is shown. It is a proportional relationship of "intercept of relationship". Thereby, the relationship between the installation area of the deposit body B and the specific surface area of the deposit body B in FIG. 5 shows that the installation area of the deposit body B is b (cm <2>), and the specific surface area of the deposit body B is c (cm <2> / g). when doing,

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

It can be represented as

8 and 9, when the deposition area A is set to a (cm 2), the slope of the relationship between the specific surface area of the deposition B and the installation area is represented by -5.0 × 10 ⁻⁷ × a. Since the intercept of the relationship between the specific surface area of the deposit B and the installation area can be represented by 0.35 × a, the relationship between the installation area of the deposit B and the specific surface area of the deposit B can be expressed as follows. have.

b = -5.0 × 10 ^-7 ac + 0.35a

Moreover, from the experiment result of FIG. 5 and FIG. 6, when the installation area b of the deposit body B is larger than the quantity shown by the relationship between the installation area of the deposit body B and the specific surface area of the deposit body B in FIG. It can be read that the retention rate is 80% or more, and the judgment becomes ○.

From the above results, in the excimer lamp provided with the deposit A containing OH group, in order to suppress the fall of illuminance, the installation area of the deposit B should just satisfy the following relationship.

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

b ≧ −5.0 × 10 ⁻⁷ ac + 0.35a.

In addition, in FIG. 7, in the excimer lamp which has the structure (1-4) as a deposit A, even if the specific surface area of the deposit B increases, the installation area of the deposit B does not become a value lower than 10 cm <2>, The relationship between the specific surface area of the deposited body B and the installation area did not become the same as when the structure A had the structure (1-1), the structure (1-2), and the structure (1-3). Therefore, in Table 7 and FIG. 8, FIG. 9, the case where the structure 1-4 is provided as the deposit body A is not considered. That is, the conditions which the installation area of the said deposit body B should satisfy are taken as the case where the structure (1-4) is provided as the deposit body A. Therefore, on the condition that the installation area of the deposit B should be satisfied, the case where the structure 1-4 is provided as the deposit A should be excluded.

When the structure (1-4) is provided as the deposit body A, since the installation area of the deposit body B is too small with respect to the inner volume of a discharge container, the effect of adsorption is not exhibited. In other words, the installation area of the deposit B is about 0.02 times the inner surface area of the discharge vessel. Therefore, about the relationship of the installation area b (cm <2>) of the deposit body B in order to suppress a fall of roughness, when the inner surface area of a discharge container is set to d (cm <2>), it is necessary to satisfy | fill the following conditions.

b ＞ 0.02d

From the above results, in the excimer lamp provided with the deposit A containing OH group, in order to suppress a fall of illuminance, it turned out that the structure of the deposit B needs to satisfy the following relationship. The installation area of the deposit A was a (cm 2), the installation area of the deposit B was b (cm 2), the specific surface area of the deposit B was c (cm 2 / g), and the inner surface area of the discharge vessel was d (cm 2). time,

^{b≥-5.0 × 10 -7 ac +} 0.35a, also, b> 0.02d

It is necessary to satisfy.

By satisfying the above relationship, it is possible to prevent the impurity gas from remaining in the discharge space without the amount of impurity gas emitted from the deposit A exceeding the amount of the impurity gas that can absorb the deposit B. Therefore, when the oxygen atom contained in the impurity gas is combined with the gas for discharge, the lowering of illuminance of excimer light emission can be suppressed, and even when the excimer lamp is turned on for a long time, the lowering of illuminance can be suppressed and the vacuum ultraviolet light can be efficiently You can exit.

In addition, the installation area a (cm <2>) of the deposit A and the installation area b (cm <2>) of the deposit B were measured, assuming that the surface of the deposit A or the deposit B was smooth without considering the irregularities of the fine particles. Say the value. Moreover, the internal surface area d (cm <2>) of a discharge container also means the value measured assuming that the surface is smooth.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory sectional drawing which shows the outline of the structure in an example of an excimer lamp of this invention, (a) sectional drawing which shows the cross section along the longitudinal direction of a discharge container, (b) A-A 'line in (a). It is a cross section.

2 is an experimental result of the excimer lamp.

3 is an experimental result of the excimer lamp.

4 is a cross-sectional view for explaining a method for measuring illuminance of an excimer lamp in an experimental example.

5 is an experimental result of the excimer lamp.

6 is an experimental result of the excimer lamp.

7 is an experimental result of an excimer lamp.

8 is an experimental result of the excimer lamp.

9 is an experimental result of the excimer lamp.

10 is an explanatory perspective view illustrating an outline of a configuration of a conventional excimer lamp.

[Description of Symbols for Main Parts of Drawing]

10 excimer lamps 11 high voltage supply electrode

12 grounding electrode 20 discharge vessel

21 Upper Wall 22 Lower Wall

23 side wall plate 24 single wall plate

30 Ultraviolet Reflective Layer 31 Deposit A

32 container B 40 aluminum

41 Support 42 UV Light Meter

S discharge space

Claims (2)

A discharge container made of silica glass having a discharge space, a pair of electrodes are provided in a state in which the silica glass forming the discharge container is interposed, and a discharge gas is enclosed in the discharge space; An excimer lamp having an ultraviolet reflecting layer formed on a portion of an inner surface of a container, The ultraviolet reflecting layer is composed of a deposit A formed in at least part of a region corresponding to one electrode, and a deposit B formed in at least a part of the region other than the region corresponding to the electrode, The deposit A is composed of silica particles containing OH groups and fine particles having a higher melting point than silica, The deposit B is composed of fine particles containing silica particles containing OH groups, An excimer lamp, characterized in that the concentration of OH groups in the silica particles constituting the ultraviolet reflecting layer is 10wtppm or more. The method according to claim 1, The installation area of the deposit A is a (cm 2), the installation area of the deposit B is b (cm 2), the specific surface area of the deposit B is c (cm 2 / g), and the inner surface area of the discharge vessel is d (cm 2). When we do, each relationship ^{b≥-5.0 × 10 -7 ac +} 0.35a, also, b> 0.02d Excimer lamp, characterized in that to satisfy.

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