TWI397942B - Excimer lamp - Google Patents

Description

Excimer lamp

The present invention relates to a discharge vessel comprising quartz glass, in which a pair of electrodes are provided in a state in which quartz glass having the discharge vessel is placed, and an excimer lamp in which excimer discharge occurs inside the discharge vessel is provided.

In recent years, a processed object formed by irradiating vacuum ultraviolet light having a wavelength of 200 nm or less on metal, glass, and other materials has been developed, and processed by the action of the vacuum ultraviolet light and the ozone generated thereby. The technique of the body is practical, for example, by a cleaning treatment technique for removing an organic contaminant attached 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.

As an apparatus for irradiating vacuum ultraviolet light, for example, an excimer molecule is formed by excimer discharge, and a light emitted from the excimer molecule, for example, an excimer lamp having a wavelength of around 170 nm is provided as a light source. In such an excimer lamp, many attempts have been made to emit higher intensity ultraviolet rays more efficiently.

Fig. 1 is a cross-sectional view for explaining the configuration of an excimer lamp, wherein (a) is a cross-sectional view showing a cross section along the longitudinal direction of the discharge vessel 2, and (b) is a line AA showing (a). Sectional view.

According to JP-A-2007-335350, the excimer lamp 1 is a discharge vessel 2 made of synthetic quartz glass that transmits ultraviolet rays, and electrodes 5 and 6 are provided inside and outside the discharge vessel 2, respectively. A part of the surface of the discharge space S exposed to the discharge vessel 2 forms the ultraviolet ray reflection film 8. The ultraviolet ray reflection film 8 is exemplified by only the cerium oxide particles and only the ultraviolet ray scattering particles containing the cerium oxide particles.

In the excimer lamp 1, in the discharge vessel 2, a light emitting portion 7 that emits ultraviolet rays generated in the discharge space S without forming the ultraviolet reflecting film 8 is formed.

According to the excimer lamp 1 having such a configuration, the surface of the discharge space S exposed to the discharge vessel 2 is provided in the discharge space S by providing the ultraviolet ray reflection film 8 in the field in which the ultraviolet ray reflection film 8 is provided. The ultraviolet rays are reflected by the ultraviolet reflecting film 8, and thus the attenuation by the transmission of the synthetic quartz glass is reduced. Further, since the ultraviolet ray reflection film 8 is reflected, the ultraviolet ray transmitting quartz glass is radiated to the outside only in the field constituting the light emitting portion 7, so that the ultraviolet ray generated in the discharge space S can be efficiently irradiated. Further, the ultraviolet ray reflection film 8 is composed mainly of cerium oxide particles, and high affinity is obtained for the discharge vessel 2 formed of synthetic quartz glass.

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

However, in recent years, the substrate of the liquid crystal panel display element to be irradiated has a large area, and the excimer lamp 1 has also been lengthened. For example, the excimer lamp 1 having a total length of more than 800 mm is required. However, in such a lengthened excimer lamp 1, the inconvenience of the discharge of the discharge vessel 2 occurs in the lighting.

The present invention has been made in an effort to solve the above problems, and an object thereof is to provide an excimer lamp that emits a vacuum ultraviolet light by generating an excimer discharge in a discharge space, and can solve an inconvenient excimer lamp in which a discharge capacitor is broken in a lighting.

According to a first aspect of the invention, there is provided a discharge vessel formed of quartz glass having a double tube structure in which an inner tube and an outer tube are disposed in a coaxial direction, and a pair of electrodes disposed in a state of quartz glass forming the discharge tube. An excimer lamp in which a quasi-molecular discharge is generated in a discharge space of the discharge vessel by enclosing a helium gas in the discharge space, wherein the inner tube is formed by fused silica glass, and the outer tube is It is formed by synthesizing quartz glass.

According to a second aspect of the present invention, in the first aspect of the invention, the discharge vessel is formed on the surface of the discharge space exposed to at least the outer peripheral surface of the inner tube, and is formed by the entire surface. An ultraviolet reflecting film composed of ultraviolet ray scattering particles of cerium oxide particles is characterized.

According to a third aspect of the present invention, in the second aspect of the invention, the inner tube is formed of electrically fused silica glass, and the ceria particle is formed by synthetic quartz glass. Its characteristics.

According to a fourth aspect of the present invention, in the second aspect of the invention, the thickness of the ultraviolet ray reflection film formed on the outer circumferential surface of the inner tube is 10 μm or more. .

According to a fifth aspect of the present invention, in the second aspect of the invention, the ultraviolet ray scattering particles include alumina particles.

According to the excimer lamp of the first aspect of the present invention, the inner tube which is likely to be a high temperature is formed of fused silica glass, and the outer tube having a lower temperature than the inner tube is formed of synthetic quartz glass. The difference in shrinkage due to thermal expansion between the outer tube and the inner tube becomes small, and the inconvenience of breaking the discharge vessel in the lighting of the excimer lamp can be solved.

Further, according to the excimer lamp of the second aspect of the invention, even if the inner tube is formed of fused silica glass, the surface of the discharge space exposed to the outer peripheral surface of the inner tube is formed in a comprehensive manner. It is possible to prevent the vacuum ultraviolet light from being irradiated on the inner tube, and the deterioration of the discharge tube can be suppressed. Therefore, even if an excimer lamp that emits vacuum ultraviolet light in the discharge space generates excimer light, the inner tube constituting the discharge vessel can be formed of fused silica glass.

Further, in the excimer lamp according to the third aspect of the present invention, the outer peripheral surface of the inner tube formed of the electrically fused silica glass is formed by forming ultraviolet ray scattering particles containing cerium oxide particles formed of synthetic quartz glass. The ultraviolet reflecting film, whereby the inner tube containing the oxygen-deficient type defect (Si-Si) reacts with the ultraviolet reflecting film containing the OH group, and is chemically coupled in the Si-H form, thereby improving the inner tube and the ultraviolet reflection The adhesion of the adhesion interface of the film can effectively prevent the ultraviolet reflective film from being peeled off.

Further, according to the excimer lamp of the present invention, the ultraviolet ray reflection film is formed on the outer peripheral surface of the inner tube to have a film thickness of 10 μm or more, and the ultraviolet ray is almost completely blocked by the ultraviolet ray reflection film, so that it can be irradiated as vacuum ultraviolet light. Go to the inner tube. Therefore, it is possible to prevent the energy of the ultraviolet rays from being accumulated in the inner tube, and it is possible to suppress deterioration due to distortion due to ultraviolet rays.

Further, according to the excimer lamp of the fifth aspect of the invention, the ultraviolet ray-reflecting film contains alumina particles, thereby preventing the cerium oxide particles and the alumina particles which are adjacent to each other by being coupled to each other while being maintained. At the grain boundary, the reflectance of the ultraviolet reflective film can be suppressed from being lowered.

Fig. 1 is a cross-sectional view for explaining the configuration of the excimer lamp 1, and Fig. 1(a) is a cross-sectional view showing a cross section along the longitudinal direction of the discharge vessel 2, and Fig. 1(b) is a view A cross-sectional view taken along line AA of Fig. 1(a).

The excimer lamp 1 is a discharge vessel 2 having a cylindrical outer tube 3 and a cylindrical inner tube 4. The discharge vessel 2 has a length of, for example, 800 to 1600 mm in the tube axis direction, a diameter of 25 to 40 mm in the outer tube 3, and a diameter of 15 to 30 mm in the inner tube 4.

The diameter of the inner tube 4 is smaller than the diameter of the outer tube 3, and the inner tube 4 is disposed inside the outer tube 3. Since the inner tube 4 is disposed along the tube axis of the outer tube 3, the discharge tube 2 has a double tube structure in which the outer tube 3 and the inner tube 4 are disposed in the coaxial direction. The side end portion 9 is formed by welding the end portions of the outer tube 3 and the inner tube 4, and the inner peripheral surface 3a of the outer tube 3 and the outer peripheral surface 4b of the inner tube 4 become an airtight space, so that it is hermetically sealed. The hermetic annular discharge space S is formed inside the discharge vessel 2.

The discharge vessel 2 is composed of quartz glass that transmits vacuum ultraviolet light well, except that the outer tube 3 and the side wall portion 9 are composed of synthetic quartz glass having a low concentration of metal impurities, and the inner tube 4 is composed of a concentration of metal impurities. It is composed of fused silica glass which is higher than synthetic quartz glass.

The outer tube 3 is in close contact with the outer peripheral surface 3b, and is provided with a mesh outer electrode 5 made of a conductive material such as a metal mesh. The outer electrode 5 is a mesh-like shape in which the discharge vessel 2 is inserted into a seamlessly woven metal wire, and light is emitted from the mesh.

The inner tube 4 is in close contact with the inner peripheral surface 4a, and is provided with a tubular inner electrode 6 made of aluminum. The inner electrode 6 is formed along the tube axis direction of the inner tube 4, but a gap in which the inner electrode 6 is not provided is formed in a range of about 20 mm from both ends in the tube axis direction. Further, the inner electrode 6 may have a C shape (groove shape) having a partial cut in a cross section.

The outer electrode 5 and the inner electrode 6 are placed in a state of being opposed to each other via the quartz glass constituting the discharge vessel 2. With such a configuration, the quartz glass constituting the discharge vessel 2 can also function as a medium.

Further, in the discharge space S of the discharge vessel 2, helium gas is sealed as a discharge gas. Here, the helium gas is formed to have a pressure in a range of, for example, 10 to 60 kPa (100 to 600 mbar) at a normal temperature.

When a high-frequency voltage is supplied between the outer electrode 5 and the inner electrode 6, a discharge vessel 2 of quartz glass functioning as a medium is interposed to generate a discharge between the electrodes. In order to prevent leakage of the surrounding member, the outer electrode 5 disposed outside the excimer lamp 1 is used as a ground electrode, and the inner electrode 6 disposed inside the excimer lamp 1 is preferably used as a supply electrode.

Since the discharge gas is sealed in the discharge space S, excimer molecules are formed by discharge between the outer electrode 5 and the inner electrode 6, and excimer discharge of vacuum ultraviolet light from the excimer molecule occurs. When helium gas is used as the discharge gas, vacuum ultraviolet rays having a peak at a wavelength of 172 nm are released.

When the excimer lamp 1 is turned on, the power supply is formed on the surface outer electrode 5 and the inner electrode 6 of the discharge vessel 2, and thus heat is transferred to the discharge vessel 2 to be warmed. The area of the outer peripheral surface 4b of the inner tube 4 exposed to the discharge space S is smaller than the area of the inner peripheral surface 3a of the outer tube 3. Since the outer electrode 5 and the inner electrode 6 are connected to the same amount of electric power, the electric power per unit area of the outer peripheral surface 4b of the inner tube 4 having a small area is larger than that of the outer tube 3. The power per unit area of the circumferential surface 3a is also large.

Further, the outer peripheral surface 3b of the outer tube 3 is exposed to the outside air and is easily dissipated, but the inner tube 4 is surrounded by the discharge space S, so that it is easy to cool the inner peripheral surface 4a of the inner tube 4 without actively cooling the inner tube 4 Heat storage. The double-structured discharge vessel 2 is constructed by the fact that in the lighting of the excimer lamp 1, the inner tube 4 is at a higher temperature than the outer tube 3.

Not limited to quartz glass, the substance has a property of increasing swelling as the temperature becomes higher. In the discharge tube 2 of the double pipe structure, the inner tube 4 is heated at a higher temperature than the outer tube 3 at the time of lighting, and is more expanded, so that the discharge of the discharge vessel 2 is inconvenient. Thus, it has been found that the outer tube 3 is composed of a member which is thermally expanded, and the inner tube 4 is constituted by a member having a small thermal expansion.

According to the glass engineering manual (Japan Chaohui Bookstore), page 488, in synthetic quartz glass, the expansion coefficient at 150 ° C is 0.54 × 10 ^-6 . K ^-1 , and the expansion coefficient at 310 ° C is 0.59 × 10 ^-6 . K ^-1 . On the one hand, in fused silica glass, the expansion coefficient at 310 ° C is 0.55 × 10 ^-6 . K ^-1 . From these values, it is known that in quartz glass, fused silica glass is less thermally expanded than quartz glass.

The inner tube 4 which is easy to be high temperature is composed of fused silica glass, and the outer tube 3 whose temperature is maintained lower than the inner tube 4 is composed of synthetic quartz glass, thereby being between the outer tube 3 and the inner tube 4 The difference in shrinkage due to thermal expansion becomes small, and the inconvenience of breaking the discharge vessel 2 in the lighting of the excimer lamp 1 can be solved.

Further, since synthetic quartz glass and fused silica glass are one type of quartz glass containing cerium oxide (SiO ₂ ) as a main component, it is easy to form a member having a different expansion ratio even if the outer tube 3 and the inner tube 4 are formed. Processing.

The excimer lamp 1 is for efficiently utilizing vacuum ultraviolet light generated by excimer discharge, and may be provided on the surface of the discharge space S of the discharge vessel 2, and an ultraviolet ray reflection film 8 formed by ultraviolet ray scattering particles may be disposed. In particular, on the outer peripheral surface 4b of the inner tube 4, the ultraviolet reflecting film 8 is entirely formed on the entire surface of the surface of the discharge space S. On the other hand, the outer tube 3 is formed of a light-emitting portion 7 that is provided with an ultraviolet ray reflection film 8 so as to be irradiated with vacuum ultraviolet rays generated in the discharge space S to the outside of the discharge vessel 2. Moreover, the ultraviolet ray reflection film 8 is formed in a part of the inner peripheral surface 3a or the outer peripheral surface 3b of the outer tube 3, and the utilization efficiency of vacuum ultraviolet light can also be improved.

The fused silica glass constituting the inner tube 4 is vacuum ultraviolet light having a wavelength of 150 nm to 380 nm which is easy to absorb light than synthetic quartz glass. The energy of the absorbed ultraviolet rays is accumulated in the discharge vessel 2, causing distortion and being easily deteriorated. However, by forming the ultraviolet ray reflection film 8 over the entire surface of the discharge space S exposed to the outer peripheral surface 4b of the inner tube 4, it is possible to prevent the vacuum ultraviolet light from being irradiated onto the inner tube 4, and the deterioration of the discharge tube 2 can be suppressed.

The ultraviolet ray reflection film 8 is composed of fine particles made of a ceramic having a high refractive index and a vacuum ultraviolet light transmission, and is specifically composed of ultraviolet ray scattering particles containing cerium oxide particles. The ultraviolet ray scattering particles are made of ceramics, thereby reducing the amount of impure gas generated from the ultraviolet ray reflection film 8, and having the characteristics of incident discharge. A part of the vacuum ultraviolet light that reaches the ultraviolet ray scattering particles is reflected on the surface of the particle, and the other part is refracted and incident on the inside of the particle, and a large amount of light incident on the inside of the particle is transmitted (partially absorbed), and then It is refracted when it is emitted. It has the function of "diffusion reflection (scattering reflection)" which repeats such reflection and refraction.

As the ultraviolet ray scattering particles constituting the ultraviolet ray reflection film 8, for example, cerium oxide particles in which fine particles of synthetic quartz glass are formed into fine particles are used. When the cerium oxide particles are composed of synthetic quartz glass and the particle diameter is, for example, in the range of 0.01 to 20 μm, the central particle diameter (peak of the number average particle diameter) is preferably 0.1 to 10 μm, more preferably 0.3. ~3.0μm. In addition, the distribution of the particle size of the cerium oxide contained in the ultraviolet ray-reflecting film 8 is preferably such that the diffusing agent is not widely distributed, and the cerium oxide particles having a particle diameter of a central particle diameter are selected to be half or more. The cerium oxide particles are preferred.

Generally, light hits a particle with a larger particle size, but if the particle size becomes smaller, the light will not reflect when it hits the particle, and scattering will occur. The scattering of light is classified into three types according to the size of the particles. When the particle diameter is smaller than the wavelength, Rayleigh scattering is generated. When the particle diameter is the same as the wavelength, the Mei scattering and the particle diameter are generated. When it is larger than the wavelength, non-selective scattering occurs.

In particular, Rayleigh scattering is characterized by the intensity of the scattered light depending on the wavelength of the light. Specifically, when the wavelength of the incident light is short, the intensity of the scattered light becomes small, and if the wavelength of the incident light is long, the intensity of the scattered light becomes small. When the Rayleigh scattering occurs in the ultraviolet ray reflection film 8, short-wavelength light of ultraviolet light or vacuum ultraviolet ray can be made into scattered light having a large light intensity.

Since the wavelength of light generated inside the discharge vessel 2 of the excimer lamp 1 is in the range of 150 nm to 380 nm, the particle diameter of the cerium oxide particles and the alumina particles is in the range of 0.01 μm to 20 μm, and When the center particle diameter is made 0.3 μm to 3.0 μm, Rayleigh scattering can be caused in the ultraviolet ray reflection film 8. Further, even if the cerium oxide particles are made smaller than the above range and the Rayleigh scattering is likely to occur, the sintering of the cerium oxide particles proceeds, and the grain boundary is eliminated, and the light scattering performance is lost.

The "particle diameter" constituting the ultraviolet ray reflection film 8 is an approximate intermediate position in the thickness direction of the cross section when the ultraviolet ray reflection film 8 is cut in the vertical direction, and is used as a viewing range by a scanning electron microscope (SEM). The expanded projection image is obtained, and the Freit's diameter of the interval of the parallel lines when the arbitrary particles of the projection image are expanded by two parallel lines in a certain direction.

In addition, the "central particle diameter" of the ultraviolet ray-reflecting film 8 is a range of the particle diameters of the maximum value and the minimum value of the particle diameters of the respective particles obtained as described above, for example, in a range of 0.1 μm. For example, it is divided into approximately 15 divisions, and the number of particles (degrees) belonging to each division is the center value of the largest division.

The cerium oxide particles constituting the ultraviolet ray scattering particles are attached to the discharge vessel 2 by local melting or the like. Generally, the values of the linear expansion coefficients are equal or similar, and have the property of being easy to follow. The cerium oxide particles are the discharge vessel 2 made of quartz glass, and the coefficient of linear expansion coefficient is approximately equal, so that the function of improving the adhesion to the discharge vessel 2 is obtained.

The inner tube 4 is preferably made of fused silica glass, especially composed of electrically fused silica glass (type 1). The electrically fused silica glass (type 1) is characterized in that the OH concentration contained in the material is extremely as low as 10 ppm or less and has an anoxic type defect (Si-Si). The electrically fused silica glass (type 1) is composed of almost cerium oxide coupled with oxygen (Si-O), but has a part of oxygen-deficient defects (Si-Si).

On the one hand, the cerium oxide particles composed of synthetic quartz glass are composed almost by coupling cerium oxide and oxygen (Si-O), but the OH group is present in a part, and the anaerobic defect (Si-Si) is Almost no. The OH group has a feature that it is easy to break the chemical coupling between atoms, and hydrogen (H) is easily made into a single feature. The cerium oxide particles composed of synthetic quartz glass have a concentration of OH contained in the material of about 300 ppm, and break the chemical coupling between the atoms, and easily become hydrogen (H) alone.

When the cerium oxide particles of the synthetic quartz glass constituting the ultraviolet ray reflection film 8 are at a high temperature of 600 ° C or higher, chemical coupling between the OH group atoms is broken, and the hydrogen gas (H) is separated so that the hydrogen gas (H) diffusion. When the ultraviolet ray reflection film 8 is adhered to the outer peripheral surface 4b of the inner tube 4 made of fused silica glass and fired at a high temperature of 600 ° C or higher, the chemical reaction of the following formula occurs.

Hydrogen gas (H) generated by the ultraviolet ray reflection film 8 diffuses and reacts with Si on one side of the oxygen-deficient type defect (Si-Si) contained in the inner tube 4, thus splitting Si-Si coupling and Si The form of -H is chemically coupled.

The oxygen-deficient defect (Si-Si) contained in the electric fused silica glass is less stable than the coupling of cerium oxide and oxygen (Si-O). Here, the OH group included in the ultraviolet ray reflection film 8 breaks the chemical bonding between the atoms to become a monomer, so that the hydrogen gas (H) gives a helping hand to the anoxic type defect (Si-Si) and splits the Si-Si coupling. Chemically coupled in the form of Si-H, which is more stable than the oxygen-deficient defect (Si-Si).

In the outer peripheral surface 4b of the inner tube 4, when the ultraviolet ray-reflecting film 8 made of the ultraviolet ray-scattering particles containing the cerium oxide particles formed of the synthetic quartz glass is formed on the surface formed by the electric fused silica glass, the inner tube is formed. 4 The interface with the ultraviolet ray reflection film 8 is such that the inner tube 4 containing the oxygen-deficient type defect (Si-Si) and the ultraviolet ray reflection film 8 containing the OH group undergo the above reaction, and are chemically coupled in the form of Si-H. Thereby, in the interface between the inner tube 4 and the ultraviolet ray reflection film 8, not only the cerium oxide particles constituting the ultraviolet ray reflection film 8 but also the fused silica glass constituting the inner tube 4 are chemically formed in the form of Si-H. Since the ground coupling is performed, the adhesion between the inner tube 4 and the ultraviolet ray reflection film 8 can be improved, and the ultraviolet ray reflection film 8 can be prevented from being peeled off.

On the other hand, the cerium oxide particles are melted by the plasma heat generated in the discharge space S of the excimer lamp 1, and the grain boundary is eliminated, so that the vacuum ultraviolet light cannot be diffused and reflected, and the reflectance is lowered. The ultraviolet ray scattering particles include not only the cerium oxide particles but also the alumina particles, so that even when exposed to the heat of the plasma, the alumina particles having a higher melting point than the cerium oxide particles are not melted. It is possible to prevent the reflectance of the ultraviolet ray reflection film 8 from being lowered by the case where the particles of the cerium oxide particles and the alumina particles adjacent to each other are coupled to each other.

The alumina particles have a particle diameter of, for example, 0.1 to 10 μm, and a central particle diameter (a peak of the number average particle diameter), for example, preferably 0.1 to 3.0 μm, more preferably 0.3 to 1.0 μm. Further, the particle size distribution of the alumina particles contained in the ultraviolet ray reflection film 8 is preferably not extended to a wide range, and the alumina particles having a particle diameter of a central particle diameter are selected to be more than half of the alumina particles. good.

The ratio of the alumina particles contained in the ultraviolet-ray reflective film 8 is, for example, 1% by weight or more, more preferably 5% by weight or more, and most preferably 10% by weight, based on the total of the cerium oxide particles and the alumina particles. Moreover, the ratio of the alumina particles contained in the ultraviolet ray reflection film 8 is preferably 70% by weight or less, and more preferably 40% by weight or less, based on the total of the cerium oxide particles and the alumina particles.

The cerium oxide particles and the alumina particles are formed by the ultraviolet ray reflection film 8 at the above-described mixing ratio, and it is possible to surely suppress the cerium oxide particles from being melted and reflect the reflectance of the ultraviolet ray absorbing film 8 even when it is lit for a long time. In the case where the ultraviolet ray reflection film 8 is adhered to the discharge vessel 2 (adhesiveness), the ultraviolet ray reflection film 8 is surely prevented from being greatly reduced. The situation of peeling off.

In addition, when the ultraviolet ray scattering particles include not only cerium oxide particles but also alumina particles, the "particle diameter" and the "central particle diameter" are not distinguished from cerium oxide particles and alumina particles, and all the measurements are used as ultraviolet scattering. particle.

The production of the cerium oxide particles and the alumina particles used as the ultraviolet ray scattering particles can be any method using a solid phase method, a liquid phase method, or a gas phase method, but in these cases, submicron is surely obtained. Granular, micron sized particles are preferred by gas phase processes, especially chemical vapor deposition (CVD).

Specifically, for example, the cerium oxide particles are reacted by reacting cerium chloride with oxygen at 900 to 1000 ° C, and the alumina particles are heated by reacting the aluminum chloride of the raw material with oxygen at 1000 to 1200 ° C. It can be synthesized, and the particle diameter can be adjusted by controlling the concentration of the raw material, the pressure of the reaction field, and the reaction temperature.

The ultraviolet ray reflection film 8 can be formed, for example, by a method called "flow down method". First, the coating liquid flowing into the discharge vessel forming material is blended. The coating liquid is composed of ultraviolet scattering particles, a binder, a dispersing agent, and a solvent. The ultraviolet ray scattering particles are, for example, ultraviolet ray scattering particles and cerium oxide particles, and the binder is a decane coupling agent containing tetraethyl orthosilicate and a dispersing agent, and the solvent is ethanol.

By containing a dispersing agent in the coating liquid, the coating liquid is gelled to easily adhere to the discharge vessel forming material, and the ultraviolet scattering particles uniformly dispersed in the coating liquid can be fixed.

The concentration of the ultraviolet ray scattering particles of the coating liquid can be adjusted by including a solvent in the coating liquid.

The coating liquid flows into the inside of the discharge vessel forming material and adheres to a predetermined field.

Thereafter, when the discharge vessel forming material to which the coating liquid adhered is heated to 1,100 ° C for 1 hour in an oxygen atmosphere, the dispersing agent is heated and disappears, leaving only the ultraviolet ray scattering particles and the binder. Since the purity of the fused silica glass is not as high as that of the synthetic quartz glass, the melting point is higher than that of the synthetic quartz glass, and heating can be performed until it is heated to 1,100 ° C.

Further, in the above, the excimer lamp 1 having the discharge tube 2 having the double tube structure in which the annular side wall portions 9 are sealed at both ends will be described. However, as shown in FIG. 2, only one side is provided. The end portion is sealed to form the annular side wall portion 9, and the other end portion is formed as a disk-shaped outer wall portion 10 that closes the outer tube 3 and a disk-shaped inner wall portion 1 that closes the inner tube 4. The excimer lamp 1 of the discharge vessel 2 of the double tube structure of the shape is also applicable.

The discharge vessel 2 is in one end portion, and the outer tube 3 and the inner tube 4 are joined by the side wall portion 9, but in the other end portion, the outer tube 3 is closed by the outer wall portion 10, and the inner tube 4 is closed. The wall portion 11 is closed, and the outer tube 3 and the inner tube 4 are not connected. Therefore, when the excimer lamp is turned on, even if the length of the expansion by the thermal expansion of the quartz glass is different between the outer tube 3 and the inner tube 4, the extension at the other end can be absorbed by the expansion and contraction. However, the stress is not concentrated on the side wall portion 9 where the outer tube 3 and the inner tube 4 are joined.

Further, the inner tube 4 which is likely to be high in temperature is composed of fused silica glass, and the outer tube 3 having a lower temperature than the inner tube 4 is made of synthetic quartz, whereby the outer tube 3 and the inner tube 4 are formed. The difference in shrinkage due to thermal expansion between the two becomes small, and the inconvenience of breaking the discharge vessel 2 in the lighting excimer lamp 1 can be solved.

Has become shown in Figure 2 The excimer lamp 1 of the discharge vessel 2 of the double tube structure of the shape is particularly suitable for the lengthy excimer lamp 1 in which the discharge vessel 2 is long in the axial direction.

Fig. 3 is a graph showing the relationship between the film thickness of the ultraviolet ray reflection film 8 and the transmittance of the light.

The vertical axis represents the transmittance (%), and the horizontal axis represents the film thickness (μm) of the ultraviolet reflective film. An ultraviolet reflecting film is formed on the surface of the test piece formed of fused silica glass, and vacuum ultraviolet light is irradiated on the surface on which the ultraviolet reflecting film is formed. Here, for the vacuum ultraviolet light having a wavelength of 172 nm, the ratio of the radiation intensity of the transmitted ultraviolet ray reflection film and the test piece to the irradiation intensity of the surface on which the ultraviolet ray reflection film is formed is expressed as the transmittance. Further, in the vacuum ultraviolet field in the range of 150 nm to 200 nm, the transmittance is known to have approximately the same tendency.

<Specification of ultraviolet reflective film>

Antimony dioxide particles: Synthetic quartz glass, particle diameter 0.1 μm to 1.0 μm, center particle diameter 0.3 μm alumina particles: high purity α alumina, particle diameter 0.1 μm to 1.0 μm, center particle diameter 0.3 μm mixing ratio: Cerium oxide particles: Alumina particles = 90% by weight: 10% by weight From the graph, it is understood that the film thickness of the ultraviolet reflecting film can be lowered, and the transmittance of vacuum ultraviolet light can be lowered. In the range where the film thickness of the ultraviolet ray reflection film is 10 μm or more, it is known that the vacuum ultraviolet light is not transmitted.

The ultraviolet reflecting film 8 is formed on the outer peripheral surface 4b of the inner tube 4 so that the film thickness is 10 μm or more, whereby the vacuum ultraviolet light is almost completely blocked in the ultraviolet reflecting film 8, and vacuum ultraviolet light is not irradiated to the inner side. Tube 4. Therefore, the energy for preventing ultraviolet rays is accumulated in the inner tube 4, and deterioration due to distortion due to ultraviolet rays can be suppressed.

Next, a verification method for distinguishing synthetic quartz glass from fused silica glass will be described.

In quartz glass, aluminum (Al), boron (B), gold (Au), iron (Fe), potassium (K), calcium (Ca), copper (Cu), lithium (Li), sodium (Na), phosphorus (P), titanium (Ti), etc. are contained as metal impurities. The metal impurities contained in the synthetic quartz glass contain only a degree close to the analysis limit (ppb level), but the fused silica glass does not contain about 1 to 20 ppm of metal impurities. Because of the investigation of the concentration of metal impurities contained in quartz glass, synthetic quartz glass and fused silica glass can be distinguished.

The size of the sample for analysis was cut out from the discharge vessel 2 as a test piece. The test piece was washed in the order of ethanol and pure water, and the surface was etched with hydrofluoric acid. The etched test piece was washed with pure water, and after being sufficiently dried, it was weighed. Thereafter, the test piece was immersed in hydrofluoric acid to dissolve it. Soluble until the shape of the test piece cannot be confirmed. By heating the quartz glass (SiO ₂ ) and the fluorine acid solution in which the metal impurities are dissolved, the cerium oxide component and the hydrogen fluoride acid are evaporated as cesium fluoride (SiF ₄ ), the metal impurity component becomes a residue, and the residue is put into the nitric acid and Sulfuric acid to dissolve metal impurities. The solution was diluted with pure water as a sample solution. The concentration of the impurity element in the sample solution was quantified using an ICP emission spectroscopic analyzer, and the converted mass was calculated. From the mass of the metal impurity to the mass of the test piece, the concentration of the metal impurity can be calculated.

Hereinafter, a verification method for distinguishing between electric fused silica glass (type 1) and oxyhydrogen fused silica glass (type 2) will be described.

In fused silica glass, there are electrically fused silica glass (type 1) and oxyhydrogen fused silica glass (type 2). The electrically fused silica glass (type 1) is characterized in that the concentration of OH contained in the material is extremely low at 10 ppm or less and has an anoxic type defect (Si-Si). On the one hand, the oxyhydroxide fused silica glass (Form 2) is OH concentration self-contained in the material of about 300 ppm, and there is almost no oxygen deficiency type defect (Si-Si). Therefore, by investigating the concentration of OH contained in the fused silica glass, it is possible to distinguish between the electrically fused silica glass (type 1) and the oxyhydrogenated fused silica glass (type 2).

The concentration of OH contained in the material of the quartz glass can be measured using an FT-IR (Fourier Transform Infrared Spectrophotometer). As the measuring device, for example, BTS-40 manufactured by Balian can be used. In the FT-IR (Fourier Transform Spectrophotometer), when infrared rays are irradiated onto a substance, and light of a certain wavelength is selectively absorbed, the concentration of OH can be obtained. Since the infrared absorption spectrum is inherent to the substance, the absorption spectrum of OH is confirmed, whereby the concentration of OH can be measured by the absorption amount of light of a specific wavelength when infrared rays are irradiated on the quartz glass.

1. . . Excimer lamp

2. . . Discharge capacitor

3. . . Lateral tube

4. . . Inner tube

5. . . Outer electrode

6. . . Inner electrode

7. . . Light exit

8. . . Ultraviolet reflective film

1(a) and 1(b) are cross-sectional views for explaining the configuration of the excimer lamp.

Fig. 2 is a cross-sectional view for explaining the structure of the excimer lamp.

Fig. 3 is a graph showing the relationship between the film thickness of the ultraviolet ray reflection film and the transmittance of light.

1. . . Excimer lamp

S. . . Discharge space

2. . . Discharge capacitor

3b. . . Peripheral surface

3. . . Lateral tube

3a. . . Inner circumference

4b. . . Peripheral surface

4. . . Inner tube

4a. . . Inner circumference

5. . . Outer electrode

6. . . Inner electrode

7. . . Light exit

8. . . Ultraviolet reflective film

9. . . Side end

Claims (3)

An excimer lamp is a discharge vessel formed of quartz glass having a double tube structure in which an inner tube and an outer tube are disposed in a coaxial direction, and a pair of electrodes are formed in a state in which quartz glass is formed in the discharge tube. An excimer lamp in which a quasi-molecular discharge is generated in the discharge space of the discharge vessel is formed in a discharge space, wherein the inner tube is formed by electrically fused silica glass, and the outer tube is Formed by synthetic quartz glass; the discharge vessel is formed over the entire surface of the discharge space exposed at least on the outer peripheral surface of the inner tube, and is formed with an ultraviolet reflective film by containing cerium oxide particles. The ultraviolet ray scattering particles are formed by quartz glass. The excimer lamp according to the first aspect of the invention, wherein the thickness of the ultraviolet ray reflection film formed on the outer circumferential surface of the inner tube is 10 μm or more. The excimer lamp according to claim 1 or 2, wherein the ultraviolet ray scattering particles comprise alumina particles.