DE102009022823A1 - Excimer lamp - Google Patents

Abstract

The invention relates to an excimer lamp having a discharge vessel of silica glass with a discharge space in which a pair of electrodes is arranged so that the silica glass of the discharge vessel is between them, in which discharge gas is filled in the discharge space and on the inner surface of the discharge vessel UV reflection layer is formed, which consists of silica particles containing OH radicals, and of fine particles having a higher melting point than silica. The concentration of OH radicals in the silica particles is at least 10 ppm by weight.

Description

The The invention relates to an excimer lamp which is to be carried out a surface treatment of an object to be treated, such as cleaning, ashing, stratification and The like is used by irradiation with UV radiation.

In In practice, an object to be treated becomes like a glass substrate a liquid crystal display, a semiconductor wafer or The like with vacuum UV radiation - ie UV radiation having a wavelength of at most 200 nm - irradiated, to him by the action of the vacuum UV radiation or of this ozone to be purified on the surface of the adhering organic contaminants to the treated article to eliminate or on the surface of the treated Object to form an oxide layer.

When Apparatus for irradiation with vacuum UV radiation, for example a device provided with an excimer lamp used in which in a discharge vessel consisting of a dielectric discharge gas is filled, in which by applying a high voltage across the discharge vessel generates an excimer discharge is and in which an excimer emission as vacuum UV radiation is broadcast. With such Excimerlampen is for an effective broadcast of even more intense UV radiation Variety of investigations carried out.

Concretely, a UV reflection layer is formed on the inner surface of the discharge vessel of the excimer lamp. In the JP-A-2007-335350 discloses a technique in which a UV reflection layer is obtained by laminating fine particles which transmit ultraviolet rays, such as silica fines or mixtures containing fine particles of silica, for example, alumina, magnesium fluoride, calcium fluoride, lithium fluoride, magnesium oxide or the like, is formed.

at an excimer lamp with such an arrangement falls from the UV radiation generated in the discharge vessel that UV radiation which is not directly towards a light emitting part is irradiated, in the UV reflection layer one. By repeated refractions and reflections on the surfaces a plurality of fine particles constituting the UV reflection layer, Diffusion reflection occurs and the UV radiation is transmitted through the light exit part emitted. As a result, the UV radiation be broadcast effectively.

For a lamp which emits UV radiation is used as the material of the Discharge vessel often, for example Used silica glass. The fine particles from which the UV reflection layer Therefore, advantageously contain particles of silica, So the same material as the discharge vessel, by a difference of the thermal expansion coefficient to Silica glass from which the discharge vessel consists, too prevent or minimize as possible and the adhesion property increase the UV reflection layer relative to the silica glass.

The article to be surface-treated often has a flat shape such as a glass substrate of a liquid crystal panel. In an excimer lamp whose light exit part consists of a discharge vessel which, like the object to be treated, has a flat shape, therefore, by reducing the gap between the light exit part and the object to be treated, the absorption of UV radiation by oxygen can be suppressed, and thus effectively perform a surface treatment. As an excimer lamp with a discharge vessel having such a shape is for example in the JP-A-2004-113984 discloses an excimer lamp with a square discharge vessel.

For an excimer lamp with a discharge vessel whose light exit part is flat, there is an in 7 shown arrangement. The excimer lamp 10 consists of a flat, rectangular discharge vessel 20 from silica glass. This discharge vessel 20 has an arrangement in which an upper wall plate 21 , a lower wall plate 22 , a sidewall plate 23 and an endwall panel 24 connected to each other, and into the discharge vessel 20 Discharge gas is filled. Further, the outer surface of the upper wall plate 21 with an electrode 11 for supplying a high voltage and the outer surface of the lower wall plate 22 with a ground electrode 12 Mistake. These electrodes 11 . 12 are arranged opposite each other. The excimer emission generated in a discharge space S passes through the lower wall plate 22 , which also functions as a light exit part, out through.

In an excimer lamp with a UV reflective layer, however, decreases during operation over a long time the degree of maintenance of the illumination intensity gradually over time. In the case of a surface treatment such as cleaning or the like, therefore, there is a disadvantage that the treatment capacity of the excimer lamp changes over the course of the operation time, even if an attempt is made to treat at a constant illumination intensity.

The Invention has been made to the disadvantage described above to eliminate in the prior art. The object of the invention is to specify an excimer lamp, which is a UV reflection layer in which also in an operation over a long time the measure of a reduction in illumination intensity is kept small and at which vacuum UV radiation effectively can escape.

The Task is according to a first aspect of the invention achieved in that the excimer lamp, which is a discharge vessel Has a silica glass with a discharge space in which a pair Electrodes are arranged so that the silica glass of the discharge vessel is located between these, in which in the discharge space Discharge gas is filled in and on the inner surface of the discharge vessel, a UV reflection layer comprising silica particles containing OH radicals, and fine particles having a higher melting point than Silica, wherein the concentration of OH radicals in the silica Particles containing the UV reflective layer, at at least 10 ppm by weight.

The Task is further according to a development the invention achieved in that the concentration of OH radicals in the silica particles of the UV reflective layer at most 502 ppm by weight.

By the mixing of fine particles with a higher melting point as silica in the UV reflective layer disappears the grain boundary due to a compound adjacent to each other fine particles prevents one another, and one can reduce the reflection factor prevent the UV reflection layer.

Further This is because the silica particles of the UV reflective layer OH radicals contain the emergence of internal defects in the Silica particles contained in the UV reflective layer are, suppressed, an absorption of light with wavelengths prevented in the UV range by the UV reflective layer, the reflection factor maintained the UV reflection layer and the degree of Reduction of the illumination intensity of the excimer lamp kept small, so that vacuum UV radiation can effectively escape.

Further One can by the measure that the concentration of OH radicals in the silica particles, from which the UV reflection layer is at least 10 ppm by weight, both the degree of maintenance the reflection as well as the degree of maintenance of the illumination intensity keep up. Thus, a remarkable effect is made the maintenance of the illumination intensity at one Operation achieved over a long time.

Further This is due to the fact that the concentration of OH radicals in the silica Particles of the UV reflection layer at most 502 wt ppm lies, an excess of oxygen atoms, which arising from the OH radicals, prevented in the discharge space and avoided that the formation of excimer molecules thereby is reduced that oxygen atoms react with noble gas atoms. One can understand the degree of maintenance of the illumination intensity the excimer lamp can continue to hold high, and vacuum UV radiation can effectively exit.

following the excimer lamp according to the invention is based on further described by drawing. Show it:

1 (a) and (b) each a schematic cross-sectional view of the arrangement of an example of an excimer lamp according to the invention, wherein 1 (a) a cross-sectional view along the longitudinal direction of the discharge vessel and 1 (b) a cross-sectional view along the line AA 'according to 1 (a) is;

2 a cross-sectional view for explaining the measuring method of the illumination intensity of the excimer lamp in a test example;

3 a graphical representation of the measurement result of the experimental example;

4 a further graphical representation of the measurement result of the experimental example;

5 a schematic cross-sectional view of the arrangement of an example of an excimer lamp according to the invention;

6 a schematic cross-sectional view of the arrangement of another example of an excimer lamp according to the invention and

7 a schematic cross-sectional view of the arrangement of a conventional excimer lamp.

1 (a) and (b) each show, in a schematic representation, the arrangement of an example of an excimer lamp according to the invention 10 , 1 (a) is a representation of the cross section along the longitudinal direction of a discharge vessel 20 , 1 (b) is a cross-sectional view along the line AA 'according to 1 (a) ,

The excimer lamp 10 has an elongate and hollow discharge vessel 20 on, whose cross-section is rectangular, whose both ends are hermetically sealed and in which a discharge space S is formed. The discharge vessel 20 consists of an upper wall plate 21 , one of the top wall plate 21 opposite lower wall plate 22 , a pair of sidewall panels 23 , which with the upper wall plate 21 as well as the lower wall plate 22 connected as well as a pair of Endwandplatten 24 which hermetically seal the two ends of a quadrilateral cylinder body made of upper wall plate 21 , lower wall plate 22 as well as the pair of sidewall panels 23 consists. The discharge vessel 20 It is made of silica glass, which transmits good UV radiation, such as synthetic quartz glass.

In the discharge vessel 20 Discharge gas is filled at a pressure of, for example, 10 kPa to 80 kPa. The change in the radiation intensity occurring over time is, however, exerted no influence, depending on what gas is selected to be the discharge gas. However, the main wavelength of the emitted excimer emission differs according to the nature of the discharge gas. For example, in an excimer lamp in which xenon (Xe) is filled, an excimer emission whose principal wavelength is 172 nm is formed. In an excimer lamp, in which a gas mixture of argon (Ar) and chlorine (Cl) is filled, produces an excimer emission whose main wavelength is 175 nm. In an excimer lamp in which a gas mixture of krypton (Kr) and iodine (I) is filled in, an excimer emission is produced whose principal wavelength is 191 nm. In an excimer lamp, in which a gas mixture of argon (Ar) and fluorine (F) is filled, produces an excimer emission whose main wavelength is at a wavelength of 193 nm. In an excimer lamp, in which a gas mixture of krypton (Kr) and bromine (Br) is filled, an excimer emission whose main wavelength is 207 nm and an excimer lamp into which a gaseous mixture of krypton (Kr) is formed and chlorine (Cl) is filled, an excimer emission is produced whose main wavelength is 222 nm.

At the discharge vessel 20 is the outer surface of the upper wall plate 21 with an electrode 11 for supplying a high voltage and the outer surface of the lower wall plate 22 with a ground electrode 12 Mistake. These electrodes 11 . 12 are arranged opposite each other. Such electrodes 11 . 12 each have a net-like arrangement and are formed in such a way that light is transmitted through the mesh of the network. As the material, for example, aluminum, nickel, gold or the like is used. They are formed, for example, by means such as screen printing or vacuum evaporation. Further, the electrodes 11 . 12 each connected to a suitable high frequency power source (not shown in the drawing).

In the excimer lamp described above 10 is the discharge space S facing inner surface of the discharge vessel 20 with a UV reflective coating 30 made of a variety of particles to effectively utilize vacuum ultraviolet radiation generated by excimer discharge. Specifically, one is the electrode 11 for supplying a high voltage corresponding portion of the inner surface of the upper wall plate 21 , the inner surfaces of the upper wall panel 21 and the lower wall plate 22 These inner surfaces are outside of the electrodes 11 . 12 corresponding areas are, as well as areas of the inner surfaces of the side wall panel 23 and the end wall panel 24 with a UV reflective coating 30 Mistake.

On the other hand, this is due to the fact that the ground electrode 12 corresponding inner surface of the lower wall plate 22 of the discharge vessel 20 not with a UV reflective coating 30 is provided Light exit part formed.

The UV reflection layer 30 has a thickness of, for example, from 5 .mu.m to 1000 .mu.m, and consists of silica particles as well as fine particles having a higher melting point than silicon dioxide and transmitting UV radiation. Among the fine particles having a higher melting point than silica and transmitting UV radiation, there are mentioned, for example, alumina, lithium fluoride, magnesium fluoride, calcium fluoride, barium fluoride and the like. No material is used which absorbs UV radiation, such as titanium, zirconium and their compounds, for the fines, unless titanium or zirconium are impurities in the UV reflective layer 30 available.

When in the UV reflective layer 30 From such fine particles which transmit UV radiation, vacuum UV radiation is incident, a part thereof is reflected by the surfaces of the fine particles, while another part is deflected, passed through the particles and again reflected or deflected by another surface. By such repeated reflections and refractions on a plurality of fine particles, the vacuum UV radiation is subjected to diffusion reflection.

However, there are cases in which silica particles are heated by the heat in the excimer lamp 10 resulting plasma melt and thereby the grain boundaries disappear, so that the vacuum UV radiation is no longer subject to diffusion reflection and thus reduces the re flexionsfaktor. On the other hand, fine particles having a higher melting point than silica do not melt even when exposed to the heat of the plasma. Therefore, by mixing the fine particles having a higher melting point than silica into the UV reflection layer 30 prevent the grain boundaries from vanishing due to a combination of adjacent fine particles, and a reduction in the reflection factor of the UV reflection layer 30 prevent.

It is advantageous if in the case of the fine particles, which in the UV reflection layer 30 contained in the manner described below, for example, in a range of 0.01 .mu.m to 20 .mu.m, and that their average grain size (maximum value of the particle size distribution corresponding to the count of the particles) in the UV reflection layer 30 for example, at 0.1 .mu.m to 10 .mu.m, preferably at 0.1 .mu.m to 3 .mu.m, is.

Here, the term "grain size" Feret the diameter to be understood, which represents the distance between parallels, when detected by a scanning electron microscope (SEM) an enlarged projection image and any particles are clamped on this enlarged projection image between two parallels in a particular direction wherein a substantially central position in the thickness direction is on a refracted surface when fractured in the surface of the UV reflective layer 30 vertical direction is considered as an observation area.

Under the term "average grain size" is intended an average of the area with the maximum number (count) on particles belonging to the corresponding area, be understood, wherein a total range of grain sizes between the maximum value and the minimum value from the for all particles determined grain sizes, which on obtained as described above, such as a range of 0.1 microns, in several areas, for example divided into about 15 areas, and for each of the areas counting the associated particles.

If at the excimer lamp 10 the electrode 11 For a supply of high voltage, an operating power is supplied, formed via the discharge vessel 20 in the discharge space S between the two electrodes 11 and 12 an excimer discharge. As a result, excimer molecules are formed, and at the same time emitted by these excimer molecules vacuum UV radiation. Some of the vacuum UV radiation generated in the discharge space S passes directly through the lower wall plate 22 , which also acts as a light exit part, outwards. Fer ner is another part of the vacuum UV radiation, although in the direction of the upper wall plate 21 broadcast. However, it is at the UV reflective layer 30 subjected to diffusion reflection and exits through the light exit part to the outside.

Characterized in that the silica particles and other fine particles of the UV reflection layer 30 have a grain size which is approximately equal to the wavelength of the vacuum UV radiation, one can effectively subject vacuum UV radiation to a diffusion reflection.

But if you have the excimer lamp 10 with the UV reflective layer 30 operates for a long time It is found that the initial illumination intensity can not be maintained and the illumination intensity gradually decreases over the course of the operation time. The inventors have examined the cause of the reduction of the illumination intensity from various sides and assumed that the reflection factor of the UV reflection layer 30 as a potential factor decreased.

Therefore, spectrums of the reflection intensity of the UV reflection layer were measured 30 the excimer lamp 10 to start of operation and spectrums of the reflection intensity of the UV reflection layer 30 the excimer lamp 10 after a long time operation and compared. Anahand this result has been demonstrated that in the UV reflective layer 30 the excimer lamp 10 after operation for a long time in the UV region, an absorption band is formed and by absorption of a part of the UV radiation by the UV radiation reflection layer 30 a reduction of the illumination intensity arises.

One can imagine that the reason for the absorption band in the UV range, which in the UV reflective layer 30 arises, in the following is:
The silica particles of the UV reflective layer 30 are damaged by the radiation during exposure to the UV radiation as well as the plasma, causing them to fail to absorb light having wavelengths in the UV range. Due to the fact that the UV radiation is absorbed due to the internal error, the diffusion reflection is suppressed.

Under The term "internal error" is intended to mean a Si-Si error with an absorption line at a wavelength of approx. 163 nm or an E 'center error (Si •) with an absorption line be understood at a wavelength of about 215 nm, which occur due to an Si-O-Si bond of the silica Particles UV radiation or plasma is exposed.

For the reason described above, it can be imagined that the internal failure to absorb light having wavelengths in the UV region occurs in the silica particles and the absorption of the light with wavelengths in the UV range, which causes a reduction of the illumination intensity of internal errors of the silica particles. Further, in the fine particles which transmit ultraviolet rays, other than silica particles, such as fine particles of alumina, lithium fluoride, magnesium fluoride, calcium fluoride, barium fluoride and the like, no radiation damage occurs even when exposed to ultraviolet rays and plasma become. One can therefore imagine that one by the emergence of the internal error in the silica particles of the UV reflective layer 30 prevents, prevents a reduction in the illumination intensity and can maintain a high degree of maintenance of the illumination intensity even when operating for a long time.

In order to prevent internal defects from occurring in the silica particles, it is effective that the silica particles contain OH radicals. By containing OH radicals, it prevents the silica particles contained in the UV reflective layer 30 contained, internal errors are generated. It is thus possible to reduce the reflection factor of the UV reflection layer 30 prevent.

The following is the method of forming the UV reflective layer 30 from fine particles containing OH-containing silica particles. In the case of the UV reflection layer 30 For example, by a wetting method in a predetermined area on the inner surface of the material of the discharge vessel, particle deposition layers containing silica particles are formed. For example, fine particles are mixed in a viscous solvent in which water is mixed with PEO resin (polyethylene oxide) to obtain a dispersion liquid. This dispersion liquid is poured into the discharge vessel. The dispersion liquid is allowed to adhere to the inner surface of the material of the discharge vessel in a predetermined range, and thereafter, by drying and firing, water and PEO resin are vaporized. This can be used to form particle deposition layers. The firing temperature is for example at 500 ° C to 1100 ° C.

An example of a method for producing silica particles containing OH radicals is heating in an electric furnace (for example, 1000 ° C) of silica particles containing no OH radicals while simultaneously supplying water vapor. This silica particles are obtained which contain a large amount of OH radicals. By using such treated silica particles can be a UV-reflective layer 30 from fine particles containing OH-containing silica particles.

Further, silica particles which do not contain OH radicals can be adhered to a predetermined area on the inner surface of the material of the discharge vessel and thereafter burned with simultaneous supply of water vapor, thus obtaining silica particles containing OH radicals. Further, one can burn silica particles containing no OH radicals, thus a UV reflection layer 30 and then heat them with simultaneous supply of steam in an electric furnace to obtain silica particles containing OH radicals.

Under the commercially available silica particles Depending on the manufacturing process, there are also products which Contain OH radicals. However, there are also products with it a low concentration of OH radicals. It is therefore preferable by the methods described above OH radicals in one to produce high concentration.

• – Man schließt das Entladungsgefäß mit einem Abzweigrohr für eine Evakuierung an eine Luftabfuhrvorrichtung an, und
• – man hält das Innere des Entladungsgefäßes bei gleichzeitiger Evakuierung durch das Abzweigrohr mittels Elektroofen auf einer hohen Temperatur.

One can regulate the concentration of OH radicals contained in the silica particles by changing the conditions of hot air removal. The excimer lamp 10 is using a process of Ausglühens, which is characterized by reheating and a slow cooling distortion in the discharge vessel 20 eliminated, and a process of hot air removal for the removal of gas contaminants contained in the discharge space S made. By appropriate selection of the condition of the hot air removal, one can determine the concentration of the OH radicals present in the silica particles of the UV reflection layer 30 are included, to regulate to desired values. This should be understood by the term "hot air removal" the following:

• - Connect the discharge vessel with a branch pipe for evacuation to an air discharge device, and
• - Keeping the inside of the discharge vessel with simultaneous evacuation through the branch pipe by means of electric furnace at a high temperature.

For example, at a hold temperature of 800 ° C, the more OH-radicals are removed, the more the hold time is increased, for example from 1 hour to 5 hours, 10 hours or 20 hours. By controlling the amount of OH radicals contained in the silica particles from the beginning, it is possible to regulate the amount of OH radicals removed by the hot air discharge, a UV reflection layer 30 of fine particles containing silica particles of any OH radical concentration.

following Be experimental examples relating to the inventive Excimer lamp shown.

Experimental Example 1

After the in 1 (a) and (b) an excimer lamp having a UV reflection layer is fabricated.

(Basic arrangement of the excimer lamp)

The Material of the discharge vessel is silica glass. The dimensions are 15 mm × 43 mm × 350 mm and the thickness 2.5 mm.

The Dimension of the electrode for the supply of a high voltage and the ground electrode is 30 mm × 300 mm.

The UV reflection layer consists of a mixture of silicon dioxide Particles with a mean particle size of 1.5 μm in an amount of 90% by weight and alumina particles with a mean particle size of 1.5 μm in a proportion of 10% by weight and is determined by the Wetting method formed, the firing temperature at 1000 ° C. lies. Xenon is filled into the discharge vessel at 40 kPa as the discharge gas.

From the excimer lamp having the above-described arrangement, 100 kinds of lamps 1 to 100 were provided with different conditions of hot air discharge. For each condition, two excimer lamps were made, one of which was broken and the initial reflectance of the UV reflective layer and the concentration of OH radicals in the silica particles were measured. The other lamp was operated uninterruptedly with a tube wall load of 0.8 W / cm ^{2 for} 500 hours. After measuring its illumination intensity, the reflection factor of the UV reflection layer was measured.

For the reflection factor of the UV reflective layer were below the fragments of the discharge vessel three arbitrary pieces selected from an area of the inner surface, in which the UV reflection layer is formed. These pieces were used as specimens. Using a spectroscopic device for vacuum UV radiation were the three specimens each with vacuum UV radiation with irradiated at a wavelength of 172 ± 5 nm, and due to the ratio of the intensity of the Reflection light to the intensity of the irradiation light the reflection factor was determined. The average value of Reflection factors of the three specimens is used as a reflection factor the UV reflective layer.

For the OH radical concentration in the silica particles became of the excimer lamps whose reflection factors were measured the UV reflective layer scraped off the discharge vessel and the scraped UV reflective layer divided into three parts. The three parts of the peeled UV reflection layers were each using a thermal desorption gas analysis method measure, and the average of the three measurement results will be referred to as the OH radical concentration in the silica particles.

following becomes the principle of measuring the OH radical concentration in the thermal Desorption gas analysis method simplified. If Silica particles containing OH radicals in a high vacuum heated, one takes place on the basis of the following chemical Formula shown reaction.

(chemical formula 1)

• 2 ≡ SiOH → H ₂ O (g) + 2SiO ₂

In a thermal desorption gas analysis, the determination of H ₂ O determines the mass of OH radicals contained in the silica particles (measured mass). Thus, one can determine the concentration of OH radicals contained in the silica particles.

The Concentration of OH radicals in the silica particles corresponds the concentration of OH radicals with respect to in the UV reflective layer containing silica particles, which cause internal errors in the UV reflective layer. The amount that contained in the peeled UV reflective layer Silica particles were determined and from this the mass the OH radicals in relation to the mass of the silica particles calculated and determined.

Hereinafter, the method for calculating the OH radical concentration in the silica particles will be described by way of example. When the mass of the peeled-off UV reflection layer is 0.20 g and the proportion of silica particles is found to be 90% by weight, the mass of the silica particles is 0.18 g. Since in the thermal desorption gas analysis method, the reaction shown in Chemical Formula 1 takes place, one molecule of H ₂ O is generated from two OH radicals. Therefore, when the amount of H ₂ O produced as the result of measurement is 1.6 × 10 ¹⁸ molecules, the number of OH radicals is 3.2 × 10 ¹⁸ molecules. Since the molecular weight of OH is 17, the mass of 3.2 × 10 ¹⁸ molecules of OH radicals 9.04 × 10 ^-5 g is determined. Since 0.18 g of silica particles contain 9.04 × 10 ^-5 g of OH radicals, the concentration of OH radicals in the silica particles is calculated to be 502 ppm by weight.

• – Die Excimerlampe 10 wurde, wie in 2 gezeigt, auf einem Stützgestell 41 aus Keramik befestigt, welches innerhalb eines Gefäßes 40 aus Aluminium angeordnet ist;
• – Ein Gerät 42 zur Messung der UV-Beleuchtungsintensität wurde an einer Stelle, welche von der Oberfläche der Excimerlampe 10 um 1 mm entfernt ist, in der Weise befestigt, dass es sich der Excimerlampe 10 gegenüber befindet;
• – In einem Zustand, in welchem die Innenatmosphäre des Gefäßes 40 aus Aluminium gegen Stickstoff ausgetauscht wurde, wurde zwischen den Elektroden 11 und 12 der Excimerlampe 10 eine Wechselhochspannung von 5.0 kV angelegt und dadurch innerhalb des Entladungsgefäßes eine Entladung erzeugt, und
• – die Beleuchtungsintensität der Xenon-Excimer-Strahlung, welche über das Netz der Masse-Elektrode 12 ausgestrahlt wird, wurde in einem Wellenlängenbereich von 150 nm bis 200 nm gemessen.

The measurement of the illumination intensity was carried out as follows:

• - The excimer lamp 10 was, as in 2 shown on a support frame 41 made of ceramic, which is inside a vessel 40 made of aluminum;
• - A machine 42 for measuring the UV illumination intensity was at a location which from the surface of the excimer lamp 10 removed by 1 mm, fixed in such a way that it is the excimer lamp 10 located opposite;
• - In a state in which the internal atmosphere of the vessel 40 aluminum for nitrogen was exchanged between the electrodes 11 and 12 the excimer lamp 10 applied a high alternating voltage of 5.0 kV, thereby generating a discharge within the discharge vessel, and
• - The illumination intensity of xenon excimer radiation, which through the network of the ground electrode 12 was measured in a wavelength range of 150 nm to 200 nm.

The illumination intensity after 15 minutes of uninterrupted operation was called the initial illumination intensity. The illumination intensity was at an uninterrupted Be of 500 hours on the basis of a relative value to the initial illumination intensity and referred to as the degree of maintenance of the illumination intensity. That is, the "intensity of illumination intensity maintenance" is denoted and calculated as [(illumination intensity after operation of 500 hours) / (illumination intensity immediately after operation)] (%).

The Excimer lamps were broken after 500 hours of operation, and as before, the reflection factor of the UV reflection layer became measured. The reflection factor after the operation of 500 hours with respect to the initial reflection factor, as the reflection-on-preservation degree and the "reflection preservation degree" becomes as [(reflection factor after operation of 500 hours) / (initial reflectance)] (%) is called and calculated.

The measurement result of the lamps 1 to 10 is shown in Table 1. Table 1 Concentration of OH radicals in silica particles / ppm by weight Reflections maintenance degrees /% Maintenance level of illumination intensity /% Lamp 1 5 78 72 Lamp 2 7 82 79 Lamp 3 10 98 96 Lamp 4 42 96 92 Lamp 5 132 96 94 Lamp 6 214 95 94 Lamp 7 341 94 93 Lamp 8 406 95 95 Lamp 9 502 97 94 Lamp 10 658 95 81

3 Fig. 12 is a graph showing the result of measurement shown in Table 1, wherein the axis of abscissa represents the concentration of OH radicals in the silica particles (ppm by weight) and the axis of ordinate represents reflection retention (%) and the values of lamps 1 to 10 were recorded. 4 is a graph of the measurement result shown in Table 1, wherein the axis of abscissa represents the concentration of OH radicals in the silica particles (ppm by weight) and the ordinate axis the degree of maintenance of the illumination intensity (%) and the values of the lamps 1 to 10 were recorded.

In the 3 and 4 The graphs shown are semilogarithmic graphs, the axes of abscissa each having a logarithmic scale.

From the result described above, it can be seen that both the reflection maintaining degree and the maintenance degree of the illumination intensity are about 80% or less than about 80%, and that when the excimer lamps are operated for a long time, the treatment capacity decreases. if the concentration of OH radicals in the silica particles is less than 10 ppm by weight, specifically 5 ppm by weight, 7 ppm by weight. On the other hand, it can be seen that, when the OH radicals in the silica particles are at least 10 ppm by weight, both the reflection maintenance degree and the illumination intensity maintenance degree reach at least 90%, and the treatment capacity becomes high even when the excimer lamps are operated can be sustained over a long time. As in 3 and 4 is shown, both the reflection maintenance level and the maintenance level of the illumination intensity increase rapidly when the OH radical concentration is increased from less than 10 ppm by weight to at least 10 ppm by weight. It is therefore possible to detect a clear difference if the concentration of OH radicals in the silica particles is set to at least 10 ppm by weight. It has been found that this results in respect of the maintenance of the illumination intensity in a long-term operation, a considerable effect is achieved.

on the other hand It was found that the degree of maintenance of the illumination intensity compared to a concentration of OH radicals in the Silica particles of 502 ppm by weight of the lamp 9 significantly more although the degree of reflection retention at a Concentration of OH radicals in the silica particles of 658 ppm by weight of the lamp 10 is maintained high. The degree of maintenance the illumination intensity at a concentration of OH radicals in the silica particles of 658 ppm by weight of Lamp 1 remains at 81%, which is about 79% which the degree of maintenance of the illumination intensity at a concentration of OH radicals in the silica particles of 7 wt ppm of the lamp 2 is located. That is, the excellent Effect with regard to the maintenance of the illumination intensity, which is obtained by the concentration of OH radicals in the silica particles to at least 10 ppm by weight is at a concentration of OH radicals of 658 ppm by weight not reached.

One can imagine that the reason for this is that in the case of too high a concentration of OH radicals in the silica particles by a reaction of the oxygen atoms, which arise from the OH radicals, with noble gas atoms, the formation of Excimer molecules is hindered and that thereby the degree of maintenance of the illumination intensity is reduced. If the concentration of OH radicals in the silica particles is too high, the OH radicals in the silica particles are heated and optically excited by being exposed to the discharge plasma and released into the discharge space as water (H ₂ O) , The released water (H ₂ O) is decomposed in the discharge plasma. An excimer lamp filled with xenon (Xe) as the discharge gas produces molecules (XeO) in which xenon atoms are linked to oxygen atoms. Of these molecules, green radiation is now emitted with a main wavelength of about 550 nm. Such a reaction of oxygen atoms with rare gas atoms hinders the formation of excimer molecules, and the maintenance of the illumination intensity of the excimer emission having a main wavelength of 172 nm decreases.

by virtue of of the phenomenon described above, a case may arise in which the degree of maintenance of the illumination intensity decreases, even if the reflection-preservation degree of UV reflective layer can be maintained high. It has therefore proved that it is also necessary to increase the concentration the OH radicals in the silica particles which are in the UV reflective layer to set at most 502 ppm by weight, an excessive presence of oxygen atoms, which arise from the OH radicals to prevent in the discharge space, such a hindrance in the formation of excimer molecules due to a reaction of oxygen atoms with noble gas atoms to prevent a reduction in the degree of maintenance of To suppress illumination intensity of the excimer lamp and at the same time an excellent maintenance effect to reach the illumination intensity which thereby is obtained that the concentration of OH radicals in the silica Particles is set to at least 10 ppm by weight.

Experimental Example 2

With Lamps where the mean grain sizes as well the proportions of silica particles and alumina particles the UV reflection layers were changed became the same Measurements carried out as in Experimental Example 1.

(Basic arrangement of the excimer lamp)

excimer as prepared in Experimental Example 1 and under the same conditions except that mean grain sizes as well Proportions of silica particles and alumina particles of the UV reflection layers changed in different ways were.

Lamp 11

• Aluminum oxide particles: mean particle size 1.5 μm
• Proportion: 20% by weight
• Silica particles: mean grain size 1.5 μm
• Proportion: 80 weight percent

Lamp 12

• Aluminum oxide particles: mean particle size 1.5 μm
• Proportion: 30 weight percent
• Silica particles: mean grain size 1.5 μm
• Proportion: 70 weight percent

Lamp 13

• Aluminum oxide particles: mean particle size 0.3 μm
• Proportion: 10% by weight
• Silica particles: mean grain size 0.3 μm
• Proportion: 90% by weight

Lamp 14

• Aluminum oxide particles: mean particle size 3.5 μm
• Proportion: 40% by weight
• Silica particles: mean grain size 0.3 μm
• Proportion: 60% by weight

Lamp 15

• Aluminum oxide particles: mean particle size 4.0 μm
• Proportion: 10% by weight
• Silica particles: mean grain size 0.5 μm
• Proportion: 90% by weight

For the excimer lamps having the above-described arrangement (lamps 11 to 15), in the same manner as in Experimental Example 1, the concentration of OH radicals in the silica particles, the reflection maintaining degree, and the maintenance level of the illumination intensity were measured. The measurement results for the lamps 11 to 15 are shown in Table 2. Table 2 component Main grain size (μm) Proportion (% by weight) Concentration of OH radicals in the silica particles (ppm by weight) Reflection maintenance degree (%) Maintenance level of illumination intensity (%) Lamp 11 Alumina particles 1.5 20 153 96 94 Silica particles 1.5 80 Lamp 12 Alumina particles 1.5 30 221 95 94 Silica particles 1.5 70 Lamp 13 Alumina particles 0.3 10 183 92 91 Silica particles 0.3 90 Lamp 14 Alumina particles 3.5 40 304 95 93 Silica particles 0.3 60 Lamp 15 Alumina particles 4.0 10 197 97 95 Silica particles 0.5 90

at the UV reflection layers of lamps 11 to 15 was the concentration the OH radicals in the silica particles in a range of at least 10 ppm by weight and at most 502 ppm by weight. It was found that the degree of reflection maintenance and the degree of maintenance of the illumination intensity these UV reflective layers are at least 90%. From these Results have been proven that even with different changes the average particle sizes and the proportions of Silica particles and alumina particles of the UV reflection layers a sufficiently high degree of reflection maintenance and a maintain a sufficiently high degree of maintenance of the illumination intensity when the concentration of OH radicals in the silica Particles of the UV reflection layer in a range of at least 10 ppm by weight and at most 502 ppm by weight.

Although an embodiment of the invention has been described above. However, the invention is not limited to the excimer lamps described above, but can also be applied to the in 5 shown excimer lamp 50 be applied by the double tube type. On the inner surface of the outer tube 52 and on the outer surface of the inner tube 53 of the discharge vessel 51 the in 5 shown excimer lamp 50 are UV reflective coatings 54 educated. The inner diameter of the outer tube 52 is 24 mm, the outer diameter of the inner tube 53 at 16 mm, the total length at 350 mm and the thickness at 1 mm. They each consist of silica glass. On the outer surface of the outer tube 52 is an outer electrode 55 of a reticulated metal and on the outer surface of the inner tube 53 an inner electrode 55 arranged from a plate-like metal.

The invention can also be applied to an angular excimer lamp 60 according to 6 be applied. In the 6 shown excimer lamp 60 has, for example, a discharge vessel 61 with a rectangular cross section made of silica glass. On opposite outer surfaces of this discharge vessel 61 is a pair of external electrodes 62 . 63 of metal arranged in such a way that they are in the tube axial direction of the discharge vessel 61 extend. In the discharge vessel 61 Xenon gas is filled in as discharge gas. On the inner surface of the discharge vessel 61 is a UV reflection layer 64 arranged. On the outer surface of the discharge vessel 61 is on any side, which does not match the outer electrodes 62 . 63 is provided, a light emission window 65 formed by that the UV reflection layer 64 not formed. The dimension of the discharge vessel 61 is 14 × 34 × 150 mm. The thickness is 2.5 mm.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 2007-335350 A [0004]
• - JP 2004-113984 A [0007]

Claims (5)

An excimer lamp comprising a discharge vessel of silica glass having a discharge space in which a pair of electrodes are arranged so that the silica glass of the discharge vessel is interposed therebetween, in which discharge gas is filled in the discharge space and a UV reflection layer is formed on the inner surface of the discharge vessel which is composed of silica particles containing OH radicals and fine particles having a higher melting point than silica, characterized in that the concentration of OH radicals in the silica particles is at least 10 ppm by weight. Excimer lamp according to Claim 1, characterized that the concentration of OH radicals in the silica particles at most 502 ppm by weight. Excimer lamp according to claim 1 or 2, characterized that of fine particles with a higher melting point are selected as silica from alumina, lithium fluoride, Magnesium fluoride, calcium fluoride or barium fluoride. Excimer lamp according to one of claims 1 to 3, characterized in that the grain size the fines having a higher melting point than silica in a range of 0.01 microns to 20 microns. Excimer lamp according to one of claims 1 to 4, characterized in that, and that the mean grain size the fines having a higher melting point than silica in the range of 0.1 .mu.m to 10 .mu.m, preferably at 0.1 μm to 3 μm.