TWI402883B - Excimer lamp - Google Patents

Description

Excimer lamp

The present invention relates to a discharge vessel formed of ruthenium dioxide glass, which is formed by providing a pair of electrodes in a state in which ceria glass forming the discharge vessel is interposed, and excimer discharge occurs inside the discharge vessel. Excimer lamp.

In recent years, a processed object made of metal, glass, and other materials by irradiating vacuum ultraviolet light having a wavelength of 200 nm or less 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 an excimer lamp that emits light having a wavelength of, for example, 170 nm from the excimer molecule 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. 9 is a cross-sectional view for explaining the structure of a conventional excimer lamp described in Japanese Patent No. 3,580,033. (a) is a cross-sectional view showing a cross section along the longitudinal direction of the discharge vessel 51. (b) is a cross-sectional view taken along line A-A of (a).

a discharge vessel 51 made of zirconia glass that transmits ultraviolet rays, On the inner side and the outer side of the discharge vessel 51, in the excimer lamp 50 formed by the electrodes 55 and 56, an ultraviolet ray reflection film 20 is formed on the surface of the discharge space S exposed to the discharge vessel 51. The ultraviolet ray reflection film 20 is exemplified in the examples only by the cerium oxide particles and only by the alumina particles (see Patent Document 1).

In the excimer lamp 50, a light emitting portion 58 that emits ultraviolet rays generated in the discharge space S without forming the ultraviolet reflecting film 20 is formed in a part of the discharge vessel 51.

The excimer lamp 50 having such a configuration is provided in the discharge space S in the field in which the ultraviolet ray reflection film 20 is provided by the ultraviolet ray reflection film 20 provided on the surface of the discharge space S exposed to the discharge vessel 51. The ultraviolet rays are reflected by the ultraviolet ray reflection film 20, and thus are not incident on the cerium oxide glass. Further, in the field in which the emitting portion 58 is formed, the ultraviolet ray transmitting cerium oxide glass is radiated to the outside, and therefore ultraviolet rays generated in the discharge space S can be effectively utilized. Further, it is possible to suppress the damage caused by the ultraviolet ray distortion of the ceria glass constituting the field other than the light exit portion 58 to be small, and it is possible to prevent the occurrence of cracks.

Further, as a discharge vessel of an excimer lamp, as shown in Patent Document 2, a rectangular cross section and a hollow shape are also used. Fig. 10 is a perspective view for explaining the configuration of a conventional excimer lamp disclosed in Japanese Laid-Open Patent Publication No. 2004-127710.

The excimer lamp 60 is a discharge vessel 61 having a rectangular cross section formed by a ceria glass that transmits ultraviolet rays and has a hollow shape, and a pair of electrodes 65 and 66 are formed on the outer surface of the discharge vessel 61. In such an excimer lamp 60 Also, an ultraviolet reflective film can be formed on the surface of the discharge space exposed to the discharge vessel 61.

Patent Document 1: Japanese Patent No. 3580233

Patent Document 2: Japanese Patent Laid-Open Publication No. 2004-127710

However, if the excimer lamp 60 shown in Fig. 10 forms an ultraviolet reflecting film. Then, the problem of reducing the uniformity of the excimer light occurs when lighting for a long time. Specifically, in the central portion of the excimer lamp 60, the illuminance is lowered as compared with the initial stage of lighting, and the illuminance at the initial stage of lighting is maintained at the end.

The present invention provides an excimer lamp which can prevent the uniformity of excimer light at the time of long-time lighting in an excimer lamp in which an ultraviolet-ray reflective film is formed on a surface of a discharge space of a discharge vessel, and has an object.

According to a first aspect of the invention, there is provided an excimer lamp comprising: a discharge vessel having a rectangular parallelepiped surface formed by a long side surface disposed opposite to each other and a short side surface connecting the long side faces; An excimer lamp in which a pair of electrodes are provided on an outer surface of the long side surface of the discharge vessel, and a helium gas is sealed in a discharge space, and an excimer discharge occurs in a discharge space of the discharge vessel. An ultraviolet reflecting film is formed on the inner surface of one of the long side faces, and an ultraviolet reflecting film formed on the inner surface of the electrode corresponding to the one long side surface is formed in the inner surface area of the short side surface. The ultraviolet ray reflection film having a thin film thickness is formed on the other long side surface with a light exit window in which the ultraviolet ray reflection film is not formed.

According to a second aspect of the present invention, in the first aspect of the invention, the ultraviolet ray reflection film formed on the inner surface of the short side surface has a thickness of 5 μm or more.

According to a third aspect of the present invention, in the first aspect of the invention, the ultraviolet ray reflection film formed on the inner surface of the long side surface has a thickness of 100 μm or less. .

According to a fourth aspect of the invention, the ultraviolet-reflecting film is composed of ultraviolet-scattering particles containing cerium oxide particles, in the invention according to any one of the first to third aspects of the present invention. Its characteristics.

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

According to the excimer lamp of the first aspect of the invention, it is considered that the film thickness is previously formed thick by sublimation of the ultraviolet reflecting film formed on the inner surface of the long side surface, and it is considered that the film thickness is formed by The ultraviolet ray reflection film on the inner surface of the short side surface is thickened by the deposition of the sublimate, and the film thickness is previously formed to be thin. By configuring the ultraviolet-ray reflective film in this manner, the film thickness is constantly maintained in a predetermined range or more, and the reflection performance of the entire ultraviolet-ray reflective film can be kept constant.

Further, in the excimer lamp according to the second aspect of the present invention, the sublimation or deposition of the ultraviolet ray reflection film makes the overall film thickness uneven, or the inner surface of the short side surface in the field of the film thickness of the ultraviolet ray reflection film is thin. In the field, when the film thickness is 5 μm or more, the reflection performance of the ultraviolet ray reflection film 20 can be made uniform as a whole.

Further, in the excimer lamp according to the third aspect of the present invention, the film thickness is reduced or thickened by sublimation or deposition of the ultraviolet ray reflection film, but only one long side of the ultraviolet ray reflection film has a thick film thickness. In the field of the inner surface of the surface, when the film thickness is 100 μm or less, generation of free oxygen released by the action of ions and photons generated by the ultraviolet ray reflection film 20 and the plasma can be suppressed, and the film can be prevented from being short. Reduce the irradiance during the time.

Further, according to the excimer lamp of the fourth aspect of the invention, the ultraviolet ray reflection film is composed of ultraviolet ray scattering particles containing cerium oxide particles, and a high affinity is obtained for a discharge vessel formed of synthetic quartz glass.

Further, in the excimer lamp according to the fifth aspect of the present invention, the ultraviolet ray-reflecting film contains alumina particles to prevent the adjacent cerium oxide particles and the alumina particles from being bonded to each other to maintain the grain boundary. The decrease in the reflectance of the ultraviolet reflective film can be suppressed.

1 is a cross-sectional view showing a schematic configuration of an example of the excimer lamp 10 of the present invention, and (a) is a cross-sectional view showing a cross section along the longitudinal direction of the discharge vessel 11, and (b) It is a cross-sectional view taken along line AA of (a).

The excimer lamp 10 is a hollow-shaped discharge vessel 11 having a rectangular cross section in which both ends are hermetically sealed and a discharge space S is formed therein, and the inside of the discharge vessel 11 is used as a discharge gas. There is a helium gas injected. Here, the helium gas is a sealing amount in a range of 10 kPa to 60 kPa (100 mbar to 600 mbar).

The discharge vessel 11 is made of cerium oxide glass which is well transmitted with vacuum ultraviolet light, such as synthetic quartz glass, and has a function as a medium.

The discharge vessel 11 is a long side surface 12a, 12b formed by long glass plates disposed opposite to each other, and is formed in a rectangular shape by a short side surface 13a, 13b connecting the long side surface 12a and the long side surface 12b. Tube. Both ends in the longitudinal direction are closed by the end faces 14a, 14b, and the inside of the discharge space S is taken as an airtight space. The discharge vessel 11 has, for example, a length in the longitudinal direction of 80 to 160 mm and a discharge space S of 320 to 640 cm ³ .

On the outer surfaces of the long side faces 12a, 12b of the discharge space 11, a pair of lattice electrodes 15, 16 are formed to face in the longitudinal direction. A functional one electrode 15 as a high voltage feeding electrode is disposed on the outer surface of the long side surface 12a, and the other electrode 16 functioning as a ground electrode is disposed on the outer surface of the long side surface 12b. Thereby, a state in which the discharge space 11 functioning as a medium is interposed between the pair of electrodes 15 and 16 is formed. Such electrodes 15 and 16 are applied, for example, by mixing a fiber-based binder with a metal powder, adding a solvent, and stirring, and applying the paste-form electrode material to the discharge vessel 11 in a grid pattern, or It can be formed by screen printing.

In the excimer lamp 10, when the lighting power is supplied to one of the electrodes 15, a discharge is generated between the electrodes 15 and 16 via the wall of the discharge vessel 11 functioning as a medium, whereby excimer is formed. Molecules, and excimer discharges emitted by vacuum ultraviolet light are generated from the excimer molecules.

In the excimer lamp 10, in order to efficiently utilize vacuum ultraviolet light generated by excimer discharge, an ultraviolet ray reflection film 20 made of ultraviolet ray scattering particles is provided on the surface of the discharge space S of the discharge vessel 11.

The ultraviolet ray reflection film 20 is a function corresponding to the long side surface 12a of the discharge vessel 11 as a high voltage feed electrode, and an inner surface area of one electrode 15 and an inner surface area continuous with the short side surfaces 13a, 13b of the field are formed. . Further, an ultraviolet reflecting film 20 is also formed in the inner surface area of the end faces 14a, 14b. On the other hand, the function of the long side surface 12b of the discharge vessel 11 serves as the inner surface area of the other electrode 16 of the ground electrode, and the light exit window 17 is constituted by the ultraviolet reflection film 20 not being formed. Further, in the field of the inner surface of the end portion of the electrode 16 on which the long side surface 12b is not formed, the reflection efficiency can be improved by forming the ultraviolet ray reflection film 20.

The ultraviolet ray reflection film 20 is an ultraviolet ray scattering particle having fine ultraviolet ray light transmissive fine particles having a high refractive index, such as cerium oxide particles and alumina particles, and reaches a portion of the vacuum ultraviolet light of the ultraviolet ray scattering particles. The surface of the particle is reflected while the other part is refracted and incident on the inside of the particle, and most of the light incident on the inside of the particle is transmitted (partially absorbed), and is refracted upon re-emission. It has a function of "diffusion reflection (scattering reflection)" which repeatedly generates such reflection and refraction.

As the ultraviolet ray scattering particles constituting the ultraviolet ray reflection film 20, for example, those in which the cerium oxide glass is powdered into fine particles can be used. The cerium oxide particles have a particle diameter of, for example, 0.01 to 2 μm, and the central particle diameter (peak of the number average particle diameter) is preferably 0.1 to 2 μm, more preferably 0.3 to 1.0 μm. Further, the particle size distribution of the cerium oxide particles contained in the ultraviolet ray reflection film 20 is preferably not extended to a wide range, and the cerium oxide particles having a particle diameter of the central particle diameter value are selected to be more than half of the dioxin. Peptide particles are preferred.

The cerium oxide particles are attached to the discharge vessel 11 by local melting or the like. In general, the values of the linear expansion coefficients are equal or similar, and have a property of being easy to follow. The cerium oxide particles are a discharge vessel 11 made of cerium oxide glass, and have the same coefficient of linear expansion coefficient, and thus have a function of improving the adhesion to the discharge vessel 11.

However, the cerium oxide particles are melted by the heat of the plasma generated in the excimer lamp 10, so that the grain boundary is eliminated, and the vacuum ultraviolet light cannot be diffused and reflected, and the reflectance is lowered. As the ultraviolet ray scattering particles, not only the cerium oxide particles but also the aluminum oxide particles, even if exposed to the heat of the plasma, the alumina particles having a higher melting point than the cerium oxide particles are not melted. Therefore, it is prevented that the particles are maintained by the particles of the cerium oxide particles and the alumina particles which are adjacent to each other by the particles.

The alumina particles have a particle diameter of, for example, 0.1 to 5 μm, and the center particle diameter (peak of the number average particle diameter) is 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 20 is preferably not extended to a wide range, and the cerium oxide particles having a particle diameter of the central particle diameter value are selected to be more than half of the alumina particles. good.

Fig. 2 is a partial cross-sectional view showing a state in which the ultraviolet ray reflection film 20 of the excimer lamp 10 of the present invention is turned on. According to the experiment or the like of the present invention, the main body of the ultraviolet ray reflection film 20 is subjected to sublimation and deposition, and it is found that the film thickness varies. Whether or not the film thickness of the ultraviolet ray reflection film 20 is changed is a cause of reducing the uniformity of excimer light.

In general, in the lighting operation of the excimer lamp 10, it is known that heat is generated by the plasma, but particularly occurs on the surface of the discharge space S of the discharge vessel 11 which is exposed to the electrode 15 or the electrode 16 formed on the outer surface. Since it is a large part of the starting point of the needle-shaped discharge called a streamer, the thermal load is large. The electrodes 15, 16 are formed on the outer surface of the discharge vessel 11, and electric power is supplied to cause excimer discharge, so that it is easy to be in a warm state. Therefore, the ultraviolet ray reflection film 20 formed on the inner surface area of the electrode 15 of the discharge vessel 11 corresponding to the long side surface 12a is heated by the plasma in the lighting of the excimer lamp 10, and The temperature of the body of the discharge vessel 11 rises and the temperature rises.

On the other hand, in the short side faces 13a, 13b where the electrodes 15, 16 are not formed on the outer surface of the discharge vessel 11, the plasma is not easily generated, and the electrodes 15, 16 are not present, and thus no power is supplied. Maintain a low temperature. The ultraviolet ray reflection film 20 formed on the inner surface area of the short side faces 13a, 13b of the discharge vessel 11 is an ultraviolet ray reflection film which is formed in the field of the inner surface corresponding to the electrode 15 in the lighting of the excimer lamp 10. 20, also keep the temperature low.

As described above, even if the ultraviolet ray reflection film 20 is formed on the surface of the discharge space S exposed to the one discharge vessel 11, a portion having a high temperature and a portion having a low temperature are generated. At a portion where the temperature is high, the ultraviolet ray scattering particles constituting the ultraviolet ray reflection film 20 are sublimated, and the fine particles 21 in the form of fine particles are generated. Since the ultraviolet ray scattering particles are small particles having a center particle diameter of about 0.1 to 2 μm, even if the respective heat capacities are small, the low temperature is liable to sublimate. A part of the ultraviolet ray reflection film 20 is sublimated as the sublimate 21, and thus is formed. The film thickness of the ultraviolet ray reflection film 20 in the inner surface area corresponding to the electrode 15 of the long side surface 12a which is continuous in the high temperature state is thinner as the lighting of the excimer lamp 10 becomes thinner.

The sublimate 21 is cooled in the discharge space S and then deposited on the inner surface of the discharge vessel 11. The sublimate 21 has a characteristic of being deposited in a cold state, and thus is more likely to accumulate at a portion where the temperature is low. The electrodes 15, 16 are formed in the discharge vessel 11 of the outer surface, and the sublimate 21 is deposited in the inner surface area of the short side faces 13a, 13b which are maintained at a low temperature. The sublimate 21 is generated from the inner surface area of the electrode 15 corresponding to the long side surface 12a, and is deposited on the inner surface area of the short side surfaces 13a, 13b, so that if the excimer lamp 10 is lit for a long time, it is formed in The film thickness of the ultraviolet ray reflection film 20 in the inner surface area corresponding to the electrode 15 of the long side surface 12a is gradually thinned, and the film thickness of the ultraviolet ray reflection film 20 formed in the inner surface area of the short side faces 13a, 13b is Gradually thicker.

Further, in the field of the inner surface of the electrode 16 which is the long side surface 12b of the light exit window 17, the electrode 16 is formed on the outer surface, and the temperature of the discharge vessel 11 is high, so that the sublimate 21 does not easily accumulate. . Therefore, it is also possible to find out that the light exit window 17 is not blocked by the accumulation of the sublimate object 21.

Fig. 3 is a perspective view showing the convection of the discharge space S of the excimer lamp 10 of the present invention.

The discharge space S inside the discharge vessel 11 is convected in the direction indicated by the arrow in Fig. 3 . From the middle of the long side face 12a, toward the short side faces 13a, 13b or the end faces 14a, 14b occur along the inner surface of the discharge vessel 11 The flow of inflows. The long side surface 12a is heated by the plasma or the electrode 15 and has a higher temperature than the other electrodes. Therefore, the luminescent gas existing around the long side surface 12a also has a high temperature. The luminescent gas having a high temperature flows in a direction toward a low temperature, and convection occurs as indicated by an arrow.

The sublimate 21 sublimated from the ultraviolet ray reflection film 20 is propagated along the convection indicated by the arrow. In the short side faces 13a, 13b, the end portions 18 close to the end faces 14a, 14b have a low temperature, so that the convection flow from the center portion of the long side face 12a toward the both end portions 18 is strong. The convection is such that the flow of the flow toward the both end portions 18 is stronger than the flow toward the central portion 19 of the short side faces 13a, 13b. Therefore, the sublimate 21 is also a part of the both end portions 18 which is more accumulated than the central portion 19.

Since the sublimate 21 is in the form of fine particles, it has reflection characteristics when it is deposited on the ultraviolet reflecting film 20. Therefore, the reflection characteristics of the ultraviolet ray reflection film 20 formed on the inner surface area of the short side faces 13a, 13b on which the sublimate 21 is deposited are improved. In particular, the reflection characteristics of the both ends 18 of the sublimate 21 are increased.

On the other hand, in the range where the film thickness is thin, the reflection performance of the ultraviolet ray reflection film 20 varies depending on the film thickness, so that the ultraviolet ray reflection is performed on the inner surface area corresponding to the electrode 15 formed on the long side surface 12a. The film 20 is obtained by sublimating the sublimate 21, and the film thickness is reduced to lower the reflection performance.

The reflection performance of the ultraviolet ray reflection film 20 in the inner surface area corresponding to the electrode 15 formed on the long side surface 12a is lowered, and the short side surfaces 13a, 13b are reflected by the sublimate substance 21 to reflect the ultraviolet ray reflection film 20. Since the performance is improved, when the excimer lamp 10 is turned on for a long period of time, the characteristics of the reflection performance of the ultraviolet ray reflection film 20 may be changed in the cross section along the short side direction of the discharge vessel 11.

Further, in the short side faces 13a, 13b, the sublimate 21 has more ends than the center portion 19, so that when the excimer lamp 10 is lit for a long time, the length of the discharge vessel 11 is along. The characteristics of the reflection performance of the ultraviolet ray reflection film 20 are changed in the cross section in the side direction.

Fig. 4(a) is a graph showing the relationship between the film thickness of the ultraviolet ray reflection film and its reflectance.

The vertical axis represents the reflectance (%) of light having a wavelength of 172 mm, and the horizontal axis represents the film thickness (μm) of the ultraviolet reflective film. An ultraviolet reflecting film was formed on the surface of the test piece made of synthetic quartz glass, and vacuum ultraviolet light was irradiated onto the surface on which the ultraviolet reflecting film was formed. Here, the ratio of the illuminance of the light of the ultraviolet ray having a wavelength of 172 nm to the illuminance reflected by the illuminance of the surface on which the ultraviolet ray reflection film is formed is shown as the reflectance. The reflectance was obtained using a spectrophotometer (VM-502, manufactured by ACTON RESEARCH). Further, in the field of vacuum ultraviolet rays having a wavelength of 150 nm to 200 nm, it is understood that the reflectance indicates the same tendency.

<Specification of ultraviolet reflective film>

Antimony dioxide particles: made of synthetic quartz glass, particle diameter 0.1μm~1μm, center particle diameter 0.3μm

Alumina particles: high purity alpha alumina, particle diameter 0.1μm~1μm , center particle size 0.3μm

Mixing ratio: cerium oxide particles: alumina particles = 90% by weight: 10% by weight

The reflectance of light of a wavelength of 172 nm of the ultraviolet-ray reflection film at the time of the film thickness of the ultraviolet-ray-reflection film in the range of 1 micrometer - 33 micrometer was measured. In the graph, the reflectance at a film thickness of 5 μm or less of the ultraviolet ray reflection film is low, but the reflectance of light having a wavelength of 172 nm when the film thickness of the ultraviolet ray reflection film is 5 μm or more is approximately constant. Further, in the range of the film thickness of the ultraviolet ray reflection film in the range of 33 μm or more and the film thickness of 40 μm to 500 μm, the reflectance of light having a wavelength of 172 nm was also confirmed to be 80%. This result is organized into a table indicating the fourth (b) figure.

In view of the fact that the ultraviolet ray reflection film 20 formed on the inner surface area of one long side surface 12a is sublimated and thinned, the film thickness is formed thicker in advance, and it is considered that it will be formed on the short side surface 13a. The ultraviolet ray reflection film 20 in the inner surface area of 13b is deposited, and the sublimate material is thickened to form a thin film thickness in advance. In other words, in the inner surface area of the short side faces 13a, 13b, a film thickness of the ultraviolet ray reflection film 20 which is thinner than the ultraviolet ray reflection film 20 of the inner surface area corresponding to the electrode 15 of the long side face 12a formed on one side is formed. . By constituting the ultraviolet ray reflection film 20 as described above, the film thickness can be maintained at 5 μm, and the reflection performance can be kept constant.

Therefore, the overall film thickness becomes uneven by the sublimation or deposition of the ultraviolet ray reflection film 20, and in the field of the inner surface of the short side surface in the field of the film thickness of the ultraviolet ray reflection film 20, if the film thickness is maintained at 5 μm or more, Regardless of the film thickness, the reflection performance of the ultraviolet ray reflection film 20 can be made uniform as a whole.

Specifically, the ultraviolet ray reflection film 20 which is formed in the inner surface area of the short side faces 13a and 13b where the sublimate material 21 is easily deposited is maintained at a low temperature, and when the film thickness is 5 μm or more at the time of production, In the initial stage of lighting, the film thickness is 5 μm, and the sublimate 21 is deposited, and the film thickness at the end of the lighting is 5 μm or more. Therefore, the reflection performance of the ultraviolet reflecting film 20 is often constant. Therefore, the ultraviolet ray reflection film 20 formed on the inner surface area of the short side faces 13a, 13b has a film thickness of 5 μm or more.

In addition, the ultraviolet ray reflection film 20 which is formed in the upper surface area corresponding to the electrode 15 of the long side surface 12a in the high state is formed to be sufficiently thick at the time of manufacture, and the film is sublimated by the sublimate 21 Thick and thin, the film thickness can be kept above 5μm at the end of lighting. In this way, by keeping the film thickness of the ultraviolet ray reflection film 20 at 5 μm or more, the reflection performance can be kept constant.

By keeping the reflection performance of the ultraviolet ray reflection film 20 constant, even if the excimer lamp 10 is lit for a long time, the uniformity of the excimer light emitted from the light emission window 17 can be maintained.

On the other hand, if the film thickness of the ultraviolet ray reflection film 20 is made too thick, the free oxygen released by the action of the ions and photons generated by the ultraviolet ray reflection film 20 and the plasma will increase, and thus the irradiance will be Reduce in a short time.

Fig. 5 is a graph showing the relationship between the film thickness of the ultraviolet ray reflection film and the change ratio of the integrated light amount.

The vertical axis is taken as the ratio (%) of the cumulative light amount, and the horizontal axis is The film thickness (μm) of the ultraviolet reflective film indicates the relationship. The excimer lamp used for the measurement is an inner surface field of a discharge vessel formed of synthetic quartz glass, and the film thickness of the ultraviolet reflection film is formed in a range of 1 μm to 1000 μm, and a gas is sealed in the discharge space, and a pair of electrodes are formed. On the outer surface of the discharge vessel. Moreover, the specification of the ultraviolet-ray reflective film is the same as the relationship between the film thickness of the ultraviolet-ray reflective film shown in FIG. 4 and the reflectance thereof.

The change ratio of the integrated light amount obtained here is a change indicating the uniformity of the tube axis direction of the discharge vessel. Specifically, 100-{(the maximum value of the integrated light amount in the tube axis direction - the minimum value of the integrated light amount in the tube axis direction) / the central value of the integrated light amount in the tube axis direction} × 100 (%) indicates the integrated light amount Change ratio. When the light emitted from the discharge vessel maintains the uniformity in the tube axis direction, the ratio of the change in the integrated light amount becomes a value close to 100%, and when the light emitted from the discharge vessel deteriorates the uniformity in the tube axis direction. Then, the ratio of change in the cumulative amount of light becomes a lower value.

The change ratio of the integrated light amount is a relative value of the phase difference in the tube axis direction of the integrated light amount. Therefore, the uniformity of light in the tube axis direction can be evaluated without being affected by the deterioration of the synthetic quartz glass constituting the discharge vessel. .

Each plot is a ratio of the change in the cumulative amount of light of the excimer lamp after a predetermined time has elapsed. a is a change ratio of the cumulative light amount after lighting for 10 hours, b is a change ratio of the integrated light amount after 100 hours of lighting, c is a change ratio of the accumulated light amount after 1000 hours of lighting, and d is a lighting The ratio of change in cumulative light amount after 5000 hours.

In addition, the "integrated light amount [mJ/cm ² ]" refers to the integral amount of the ultraviolet illuminance that is measured by the ultraviolet illuminance at a predetermined speed from a predetermined distance (specifically, 3 mm) from the ultraviolet radiation surface of the excimer lamp. The spotlight is turned on for 1 minute, and the spotlight is turned off at the point where the light is turned off for 1 minute. In the state where the total lighting time has elapsed for a predetermined period of time, the electrode width of the excimer lamp is equally measured in the direction of the tube axis 20 Cumulative amount of light.

In the graph, the film thickness of the ultraviolet ray reflection film is 100 μm or less, and the ratio of change in the integrated light amount is close to 100%, and the cumulative light amount after the lighting for 10 hours and 5000 hours after lighting is reduced by only about 2%. However, when the film thickness of the ultraviolet ray reflection film is 100 μm or more, the ratio of change in the integrated light amount gradually increases as the film thickness increases, and the longer the lighting time is, the more the integrated light amount is greatly reduced. The particles generated by the plasma and the photons act as a large number of particles, and the free oxygen generated by the action reacts with xenon (Xe) enclosed in the discharge space to form xenon oxide (XeO), which is a discharge gas. Insufficient enthalpy leads to reduced luminous efficiency.

The film thickness is thinned or thickened by sublimation or deposition of the ultraviolet reflecting film, but in the field of the inner surface of one long side surface of the field of the thick film thickness of the ultraviolet reflecting film, if the film thickness is made At 100 μm, free oxygen released by the action of ions and photons generated by the ultraviolet reflecting film and the plasma does not occur, and the phenomenon of reducing the irradiance in a short time can be prevented.

Specifically, the ultraviolet ray reflection film 20 formed on the inner surface of the long side surface 12a in which the film thickness is gradually thinned by the sublimation object 21 is sublimated, and it is preferable to form a film thickness at the time of manufacture. However, in order to suppress the decrease in illuminance depending on free oxygen, the film thickness must be 100 μm or less. In other words The ultraviolet ray reflection film 20 formed on the inner surface of the long side surface 12a is such that the sublimate material 21 is thinned by sublimation as the excimer lamp 10 is turned on, but the thickness is not thickened on the contrary. Therefore, when the film thickness is formed to 100 μm or less in the initial stage of lighting, the decrease in illuminance due to free oxygen can be suppressed.

The ultraviolet ray reflection film 20 formed on the inner surface of the short side faces 13a, 13b is formed by stacking the sublimate 21 as the excimer lamp 10 is turned on, so that it is as much as possible in manufacturing. The film thickness is thin, and specifically, it is preferably about 5 μm. When the thickness of the ultraviolet ray reflection film 20 is sufficiently thin in the initial stage of lighting, the film thickness is gradually increased by the deposition of the sublimate 21, and the film thickness is kept at 100 μm or less even at the end of lighting. The decrease in the irradiance caused by the increase in the thickness of the film is suppressed.

Hereinafter, a method of forming the ultraviolet reflecting film 20 on the inner surface area of the discharge vessel 11 will be described.

The ultraviolet ray reflection film 20 can be carried out, for example, by a method called "flow down method". First, the coating liquid flowing into the inside of the discharge vessel forming material is prepared. The coating liquid is composed of ultraviolet scattering particles, a binder, a dispersing agent, and a solvent. The ultraviolet ray scattering particles are cerium oxide particles and alumina particles, the binder is tetraethyl orthosilicate, the dispersing agent is a decane coupling agent, and the solvent is ethanol.

By containing a dispersing agent in the coating liquid, the coating liquid is gelated to form an ultraviolet ray scattering particle which is easily adhered to the discharge vessel forming material and which is uniformly dispersed in the coating liquid.

Adjusting the UV scattering of the coating solution by containing a solvent in the coating liquid The concentration of the particles.

The coating liquid flows into the inside of the discharge vessel forming material and adheres to a predetermined area of the inner surface. The solvent was evaporated by natural drying in this state.

Thereafter, after heating in an oxygen atmosphere for 1 hour and heating to 1000 ° C, the dispersant is heated and disappeared, leaving only the ultraviolet ray scattering particles and the binder. The binder is cerium oxide and is fused to the ultraviolet ray scattering particles, and the adhesion between the particles and the material of the discharge vessel is increased.

When the above-mentioned work is applied to the inner surface area of the short side surface 13a or the short side surface 13b, and to the inner surface area of the long side surface 12a, it is repeated three times, and on the short side surface 13a, 13b. The inner surface area and the inner surface area of the long side surface 12a can form the ultraviolet ray reflection film 20 having a different film thickness.

Further, as shown in Fig. 6, in the state where the material of the discharge vessel is tilted, by repeating the above-described work only by flowing the coating liquid on the inner side, the inner surface areas of the short side faces 13a, 13b are In the inner surface region of the long side surface 12a, the ultraviolet ray reflection film 20 having a different film thickness can be formed. First, as shown in Fig. 6(a), the ultraviolet reflecting film 20 is formed on the short side surface 13b of the discharge vessel forming material and the inner surface area of the long side surface 12a. Thereafter, as shown in Fig. 6(b), the ultraviolet reflecting film 20 is formed in the inner surface areas of the short side surface 13b and the long side surface 12a of the discharge vessel forming material, and the inner surface areas of the short side faces 13a, 13b are formed. Since the coating liquid is applied only once, the ultraviolet reflecting film 20 of one layer is formed, but the coating liquid flows twice in the inner surface area of the long side surface 12a, thereby forming two layers of ultraviolet reflection. Membrane 20. Therefore, ultraviolet rays formed in the inner surface area of the long side surface 12a can be formed. The film thickness of the reflective film 20 is made thicker than the thickness of the ultraviolet reflecting film 20 formed on the inner surface area of the short side faces 13a, 13b.

In the following, an example will be described with respect to an integrated light amount of excimer light when a long-term lighting of an excimer lamp in which an ultraviolet-ray reflective film is formed on the inner surface of a discharge vessel is used.

Experimental example 1

The ultraviolet ray reflection film is formed on the inner surface area of the discharge vessel, and the cumulative light amount at the initial stage of lighting and the integrated light amount at the end of lighting are measured along the tube axis direction of the excimer lamp. In the UV/ozone cleaning of the glass substrate used for the excimer lamp, the glass substrate is passed through the excimer lamp, and the organic matter is decomposed by the action of UV and ozone. Since the cleaning action depends on the cumulative amount of light, the cumulative amount of light [mJ/cm ² ] can be utilized as a standard for the cleaning performance of the excimer lamp.

The excimer lamp used in the experiment was a discharge vessel made of synthetic glass, and had an outer diameter of 15 mm × 42 mm × 1200 mm and a thickness of 2.0 mm. A 30 kPa helium gas was sealed inside the discharge vessel. An electrode having a size of 30 mm × 1000 mm was placed on the outer surface of the long side surface of the discharge vessel.

Further, in the field of the inner surface of the discharge vessel, an ultraviolet ray reflection film formed of cerium oxide particles and alumina particles is formed. The central particle diameter of the ultraviolet ray scattering particles formed by the cerium oxide particles and the alumina particles is 0.3 μm, and the composition ratio of the cerium oxide particles to the alumina particles is 9:1 by weight. At the time of manufacture, the film thickness of the ultraviolet-ray reflection film formed in the inner surface area of the long side surface of one of the discharge vessels is formed as 40 μm. The film thickness of the ultraviolet reflecting film in the inner surface area of the two short side faces of the discharge vessel was 5 μm.

The cumulative amount of light was measured using an ultraviolet illuminometer manufactured by Nippon Oxtail Motor, UIT-150/VUV-172S. The above-mentioned excimer lamp is placed on the upper portion of the small roller conveyor, and the ultraviolet illuminometer is conveyed at a constant speed (5 m/min) at a position of 3 mm below, and the electrode width of the excimer lamp is equally divided in the tube axis direction 20 The cumulative amount of light at each part was measured.

Fig. 7 is a graph showing the experimental results of Experimental Example 1.

The vertical axis was taken as the cumulative light amount [mJ/cm ² ], and the horizontal axis was taken as the position in the tube axis direction of the excimer lamp, and the experimental results were plotted. The horizontal axis indicates that one end portion of the excimer lamp in the longitudinal direction is 0 mm, and indicates a separation distance therefrom. Further, the section H is a position indicating that the electrode is formed on the long side surface of the discharge vessel. A is a state indicating the initial stage of lighting, and B is a state indicating the end of lighting.

The excimer lamp at the initial stage of lighting refers to a state in which the excimer discharge is stable after one hour of lighting in the excimer lamp completed as a product. The excimer lamp at the end of the lighting refers to the state in which the excimer lamp at the beginning of the lighting is turned on for 1 minute, the point at which the light is turned off for 1 minute is turned off, and the time after the line lighting has passed 1000 hours.

In the state of the initial A of the lighting, or the state of the end of the lighting B, the cumulative amount of light of the excimer lamp is uniform except for the end. The end of the excimer lamp is for the angular characteristics of the light-emitting portion and the ultraviolet illuminometer, and generally reduces the amount of accumulated light. Further, in the end of the lighting B, in order to reduce the transmittance of the synthetic quartz glass which is turned on for a long time, the amount of integrated light is lowered, but it is known that it can be maintained. The uniformity of excimer light.

Experimental example 2

When the ultraviolet reflective film is placed at a position on the inner surface of the discharge vessel, or when the film thickness is changed, the cumulative amount of light at the end of the lighting is measured.

For the excimer lamp similar to the user of Experimental Example 1, four kinds of excimer lamps for changing the method of forming the ultraviolet ray reflection film were used as experimental objects. The light was turned on for 1 minute, the light was turned off at 1 minute, and the accumulated light amount [mJ/cm ² ] was measured at the end of the lighting after 1000 hours of the total lighting time.

Fig. 8 is a graph showing the experimental results of Experimental Example 2.

The vertical axis was taken as the cumulative light amount [mJ/cm ² ], and the horizontal axis was taken as the position in the tube axis direction of the excimer lamp, and the experimental results were plotted. The horizontal axis indicates that one end portion of the excimer lamp in the longitudinal direction is 0 mm, and indicates a separation distance therefrom. Further, the section H is a position indicating that the electrode is formed on the long side surface of the discharge vessel. C is an initial integrated light amount distribution of the excimer lamp in which only the ultraviolet reflecting film is provided on the inner surface of the long side surface (12a) of the discharge vessel, D is an integrated light amount distribution indicating the end of life of C, and E is a film thickness of 5 μm. The ultraviolet ray reflection film is provided on the initial integrated light amount distribution of the excimer lamp of the long side surface (12a) and the short side surface (13a, 13b), and F is the integrated light quantity distribution of the end of life of E.

From the experimental results C, D, an excimer lamp provided with only an ultraviolet reflecting film on the inner surface of the long side surface (12a) is the end of life, and the ultraviolet ray is reversed. When the film is heated by the heat of the plasma, it will sublimate and a sublimate substance will be formed. Further, in the inner surface area of the short side surface in which the temperature is maintained at a low state, a sublimate is deposited. However, since the sublimate is propagated along the convective flow of the enclosed gas in the discharge space, the accumulation of the sublimate does not occur uniformly in the tube axis direction of the discharge vessel.

Therefore, as the end of life is reached, the ultraviolet ray reflection film formed on the inner surface of the long side surface (12a) is thinned, and the reflectance is lowered. Also, the synthetic quartz glass forming the discharge vessel is also deteriorated in transmittance due to deterioration. However, at both ends in the tube axis direction of the excimer lamp, the accumulation of the sublimate on the short side surface is increased, so that the accumulated sublimate is reflected and the accumulated light amount at both ends in the tube axis direction is suppressed. The reduction. Therefore, the end of life D is a distribution in which the integrated light amount in the central portion of the tube axis direction is drastically decreased, not only the total integrated light amount is lowered. At the cumulative light amount distribution such as the end of life D, such as washing unevenness occurs in a washing apparatus in which a workpiece is processed under the excimer lamp. When only the ultraviolet reflecting film is formed on the inner surface of the long side surface (12a), it is understood that the uniformity of the excimer light is lowered.

From the experimental results E, F, in the excimer lamp having an ultraviolet reflecting film having a film thickness of 5 μm on both the long side surface (12a) and the short side surface (13a, 13b), the ultraviolet light reflection in the inner surface area of the short side surface Since the film thickness of the film is maintained at 5 μm or more, the decrease in the integrated light amount is small. However, in the central portion of the discharge tube in the tube axis direction, the accumulation of the ultraviolet ray reflection film in the inner surface area is less than the both ends in the tube axis direction, and the ultraviolet ray reflection film in the inner surface area of the long side surface becomes Therefore, the decrease in the integrated light amount in the central portion of the excimer lamp in the tube axis direction is large. Therefore, life expectancy The final phase F is a distribution in which the integrated light amount in the central portion in the tube axis direction is particularly rapidly decreased. The cumulative light amount distribution at the end of life F, for example, causes a washing unevenness in a washing apparatus in which the operation is performed under the excimer lamp. Even when the ultraviolet ray reflection film is formed on both the long side surface (12a) and the short side surface (13a, 13b), it is understood that the film thickness is 5 μm at the time of manufacture, and the uniformity of the excimer light can be reduced.

Further, as a reference experiment, an excimer lamp provided with an ultraviolet-ray reflective film having a thickness of 100 μm was produced on each of the long side surface (12a) and the short side surface (13a, 13b), and the integrated light amount in the initial state of lighting was measured. The cumulative equivalent of the state of the lamp after 200 hours. The measurement position was made in the same 20 points as the other experiments.

In the reference experiment, the cumulative amount of light after lighting for 200 hours was as low as 62% (38% reduction) compared with the cumulative amount of light at the beginning of lighting. Therefore, since the thickness of the ultraviolet ray reflection film formed on the long side surface is thick, free oxygen is generated by the action of ions and photons generated by the plasma of the ultraviolet ray reflection film depending on the lighting operation of the molecular lamp. The reason for reducing the efficiency of ultraviolet light generation in the excimer discharge gas is to cause a decrease in the cumulative amount of light.

10‧‧‧Excimer lamp

11‧‧‧Discharger

12a, 12b‧‧‧ long side

13a, 13b‧‧‧ short side

14a, 14b‧‧‧ end face

15,16‧‧‧ electrodes

17‧‧‧Light shot window

20‧‧‧UV reflective film

21‧‧‧ Sublimate

1(a) and 1(b) are cross-sectional views for explaining a schematic configuration of an example of the excimer lamp of the present invention.

Fig. 2 is a partial cross-sectional view showing the excimer lamp of the present invention.

Figure 3 is a view showing the discharge space of the excimer lamp for explaining the present invention. Stereo view of the convection.

Fig. 4(a) and Fig. 4(b) are graphs showing the relationship between the film thickness of the ultraviolet ray reflection film and its reflection characteristics.

Fig. 5 is a graph showing the relationship between the film thickness of the ultraviolet ray reflection film and the change ratio of the integrated light amount.

6(a) and 6(b) are cross-sectional views for explaining a method of forming an ultraviolet-ray reflective film of the excimer lamp of the present invention.

Figure 7 is a graph showing the results of the experiment.

Figure 8 is a graph showing the results of the experiment.

9(a) and 9(b) are cross-sectional views for explaining the outline of a conventional excimer lamp.

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

10‧‧‧Excimer lamp

11‧‧‧Discharger

12a, 12b‧‧‧ long side

13a, 13b‧‧‧ short side

14a, 14b‧‧‧ end face

15,16‧‧‧ electrodes

17‧‧‧Light shot window

20‧‧‧UV reflective film

S‧‧‧discharge space

A‧‧‧In the early days of lighting

Claims (5)

An excimer lamp is a discharge vessel having a long side surface disposed opposite to each other and a tube having a rectangular cross section formed on a short side surface connecting the long side surfaces, and the long side of the discharge vessel An outer surface of the surface is provided with a pair of electrodes, and an excimer lamp in which a quasi-molecular discharge is generated in a discharge space of the discharge vessel is formed in a discharge space of the discharge vessel, and is characterized in that: An ultraviolet reflecting film is formed on the inner surface of the long side surface, and a film thinner than the ultraviolet reflecting film formed on the inner surface of the electrode corresponding to the one long side surface is formed in the inner surface of the short side surface. The thick ultraviolet ray reflection film has a light exit window in which the ultraviolet ray reflection film is not formed on the other long side surface. The excimer lamp according to claim 1, wherein the ultraviolet reflective film formed on the inner surface of the short side surface has a film thickness of 5 μm or more. The excimer lamp according to the first or second aspect of the invention, wherein the thickness of the ultraviolet ray reflection film formed on the inner surface of the one long side surface is 100 μm or less. The excimer lamp according to claim 1 or 2, wherein the ultraviolet ray reflection film is composed of ultraviolet ray scattering particles containing cerium oxide particles. The excimer lamp according to claim 4, wherein the ultraviolet ray scattering particles comprise alumina particles.