TW202414509A - excimer lamp - Google Patents

Abstract

The subject of the present invention is to provide an excimer lamp that suppresses both ultraviolet deformation of a discharge capacitor and deviation of the illuminance maintenance rate corresponding to the location of the discharge capacitor. The excimer lamp of the solution comprises a long discharge capacitor including fluorine-doped quartz glass and sealing a luminescent gas therein, and a pair of electrodes for applying a discharge voltage to the interior of the discharge capacitor. In the effective luminescent region of the discharge capacitor, the virtual temperature T[℃] of each measuring portion consisting of a pair of end portions in the longitudinal direction and a plurality of intermediate portions obtained by substantially equally dividing the region between the pair of end portions in the longitudinal direction by a predetermined number satisfies the following equations (1) and (2) when the median value of the virtual temperature T[℃] of each measuring portion is set to Ta[℃],

Description

Excimer lamp

The present invention relates to an excimer lamp, and more particularly to an excimer lamp in which a discharge capacitor is doped with fluorine.

Excimer lamps that emit ultraviolet light have a certain luminescent gas sealed in a discharge capacitor made of quartz glass.

When the excimer lamp is continuously lit, the ultraviolet rays generated in the discharge space will deform the quartz glass forming the discharge capacitor when passing through it, which may cause the glass to break. This problem is particularly prominent in excimer lamps that emit short-wavelength ultraviolet rays (also called vacuum ultraviolet rays) with a peak wavelength of less than 200nm.

Furthermore, even if the glass itself is not damaged, since quartz glass absorbs ultraviolet rays, structural defects will occur in the molecules constituting quartz glass, and these defects will increase the amount of ultraviolet rays absorbed. As a result, the transmittance of the discharge capacitor itself will decrease, which may lead to a decrease in illuminance.

In view of this situation, it is important to suppress ultraviolet deformation as much as possible in the discharge capacitor of the excimer lamp, and several technologies have been proposed so far.

One of the reasons for the generation of ultraviolet absorption bands in quartz glass is the unstable structure in quartz glass, more specifically, the three-membered ring structure and the four-membered ring structure. These unstable structures have weaker binding energy than normal structures, so the more unstable structures there are, the lower the transmittance of ultraviolet light.

It is known that the unstable structure depends on the virtual temperature of the quartz glass. The lower the virtual temperature, the less the unstable structure is generated. As a means of changing the virtual temperature of the quartz glass, a method of heat treatment in a furnace is known. In order to lower the virtual temperature of the quartz glass, it can be achieved by heat treatment at a low temperature. However, when the desired virtual temperature is low, a long heat treatment time is often required. From the perspective of industrial production of excimer lamps, it is not ideal to have a very long heat treatment time. For example, if the virtual time is set to about 500°C, the heat treatment time may reach more than 1 month.

It is also known that when fluorine (F) is contained in quartz glass, Si-F bonds are generated, thereby having the effect of alleviating the above-mentioned unstable structure. That is, by introducing fluorine into quartz glass, the amount of unstable structure generated can be reduced while the heat treatment time is relatively shortened.

The applicant has previously proposed an excimer lamp using synthetic quartz glass with a fluorine content of 7000 wt.ppm to 30000 wt.ppm and a virtual temperature of 750°C to 1000°C as a discharge capacitor (see Patent Document 1). [Prior Art] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2008-192351

[The problem that the invention wants to solve]

The inventors of the present invention have made intensive studies and have newly discovered that when an excimer lamp using quartz glass containing fluorine as a discharge capacitor is lit for a long time, the illuminance varies depending on the location of the discharge capacitor. In other words, the inventors of the present invention have newly discovered that in an excimer lamp using quartz glass containing fluorine as a discharge capacitor, the illuminance maintenance factor varies depending on the location of the discharge capacitor.

The present invention is made in view of the above-mentioned problem, and its object is to provide an excimer lamp which suppresses both the ultraviolet deformation of the discharge capacitor and the deviation of the illuminance maintenance rate corresponding to the location of the discharge capacitor. [Means for solving the problem]

The excimer lamp of the present invention is characterized by comprising: a long strip-shaped discharge capacitor comprising fluorine-doped quartz glass and sealing a luminescent gas therein; and a pair of electrodes for applying a discharge voltage to the interior of the discharge capacitor; the virtual temperature T[°C] of each measuring portion of the discharge capacitor in the effective luminescent region, which is composed of a pair of end portions in the long-side direction and a plurality of middle portions obtained by substantially equally dividing the region between the pair of end portions in the long-side direction by a predetermined number, satisfies the following equations (1) and (2) when the middle value of the virtual temperature T[°C] of each measuring portion is set to Ta[°C],

Through intensive research by the inventors, it was found that the reason why the illumination maintenance factor varies depending on the location of the discharge capacitor is that the virtual temperature of the discharge capacitor varies during the manufacturing process.

As mentioned above, when the ultraviolet light generated in the discharge space of the excimer lamp passes through the quartz glass forming the discharge capacitor, there is a problem of causing the quartz glass to deform. It is known that this problem can be solved by slowing down the cooling speed during the manufacture of the excimer lamp to reduce the virtual temperature of the quartz glass.

However, the above method has another problem that the manufacturing time is too long when manufacturing excimer lamps for industrial use. Therefore, from the viewpoint of making the cooling speed relatively fast and making it easy to lower the virtual temperature of quartz glass, as described in the above-mentioned Patent Document 1, a method of using fluorine-doped quartz glass as a discharge capacitor has been developed.

However, cooling the quartz glass at a faster cooling rate tends to make the virtual temperature of the quartz glass non-uniform. That is, by doping with fluorine, the virtual temperature of the quartz glass is easily lowered at the same cooling time, but on the other hand, another problem becomes prominent that the virtual temperature of each location in the manufactured discharge capacitor tends to vary.

In particular, when an excimer lamp has a long discharge capacitor, the virtual temperature tends to vary depending on the position in the long-side direction. This virtual temperature variation induces a variation in the illuminance maintenance rate for each location after long-term lighting. In other words, due to long-term lighting, the brightness tends to vary depending on the location of the discharge capacitor. This problem is particularly prominent in an excimer lamp having a discharge capacitor that is longer than 1m in the long-side direction.

Excimer lamps are mainly used for industrial purposes. For example, by enclosing a luminescent gas whose main component is Xe, an excimer lamp becomes a vacuum ultraviolet light source with a peak wavelength of around 172nm. This light source is used, for example, for surface modification or cleaning of wafers. At this time, if the brightness varies at each location of the discharge capacitor due to long-term lighting, it is expected that the degree of processing of the processed object will vary at each location.

Therefore, in excimer lamps, it is desirable to minimize the variation in the illuminance maintenance factor regardless of the location in the discharge capacitor. However, in order to suppress the variation in virtual temperature, which is one of the causes of the variation in the illuminance maintenance factor, the cooling rate must be extremely slow, and as mentioned above, this method is difficult to adopt in view of industrial production.

In contrast, an excimer lamp that satisfies the above equations (1) and (2) can suppress the deviation of the illuminance maintenance rate while allowing the deviation of the virtual temperature to a certain extent. Therefore, the time required for manufacturing the excimer lamp will not be greatly extended, and the brightness deviation after long-term lighting can be suppressed. The details will be described later in the "Implementation Method" section.

The aforementioned excimer lamp may have a maximum value and a minimum value of the aforementioned virtual temperature T at each measurement location that differ by more than 10°C. [Effect of the invention]

According to the present invention, it is possible to realize an excimer lamp that suppresses both ultraviolet deformation of a discharge capacitor and deviation in the illuminance maintenance factor corresponding to a location of the discharge capacitor without significantly increasing the production cycle time.

The embodiments of the excimer lamp of the present invention will be described with reference to the drawings as appropriate. The following drawings are schematic illustrations, and the size ratios in the drawings are not necessarily consistent with the actual size ratios. Furthermore, the size ratios between the drawings are not necessarily consistent.

FIG. 1 is a top view schematically showing the structure of an excimer lamp 1 of the present embodiment. The excimer lamp 1 has a long discharge capacitor 10 made mainly of fluorine-doped quartz glass and bases (31, 32) provided at both ends of the discharge capacitor 10. The bases (31, 32) are provided for the purpose of fixing the ends of the discharge capacitor 10, but are not essential in the present invention. In the following description, reference is made to the X-Y-Z coordinate system shown in FIG. 1 as appropriate. In addition, when expressing a direction, when distinguishing between positive and negative directions, positive and negative signs are added, such as "+X direction" and "-X direction", and when expressing a direction without distinguishing between positive and negative directions, it is simply recorded as "X direction".

In the excimer lamp 1 of the present embodiment, the length of the discharge capacitor 10 in the X direction is 1 m or more. However, the present invention can also be applied to an excimer lamp 1 in which the length of the discharge capacitor 10 in the X direction is less than 1 m.

It is known that the transmittance of ultraviolet light in quartz glass is affected by the concentration of OH groups contained in the quartz glass. Specifically, when the concentration of OH groups contained in the quartz glass is high, the transmittance to short-wavelength light is low, and conversely, when the concentration of OH groups is low, the transmittance to short-wavelength light becomes high.

In the present invention, the concentration of OH groups contained in the quartz glass constituting the discharge capacitor 10 is arbitrary, but from the viewpoint of improving the efficiency of extracting the ultraviolet rays generated in the discharge capacitor 10 to the outside of the discharge capacitor 10, the OH group concentration is preferably lower.

When the concentration of OH groups contained in the quartz glass is high, the durability of the quartz glass is improved. However, by introducing fluorine into the quartz glass, the instability of the structure can be eliminated and the durability of the quartz glass can be increased. That is, when fluorine is doped into the quartz glass, even if the concentration of OH groups contained in the quartz glass is reduced, quartz glass showing higher durability can be realized. From this point of view, the concentration of OH groups contained in the quartz glass constituting the discharge capacitor 10 is preferably 10wt.ppm to 450wt.ppm.

In the present invention, the concentration of fluorine doped in the quartz glass constituting the discharge capacitor 10 is arbitrary. However, if the fluorine concentration is too high, the ultraviolet rays generated in the excimer lamp 1 may cause oxygen deficiency defects in the quartz glass constituting the discharge capacitor 10. On the other hand, if the fluorine concentration is too low, the effect of lowering the virtual temperature of the quartz glass is almost not obtained. From this point of view, the fluorine concentration of the quartz glass constituting the discharge capacitor 10 is preferably 10wt.ppm to 3000wt.ppm.

The concentration of OH groups contained in quartz glass can be calculated based on the absorbance around a wavelength of 3670 cm ^-1 obtained by measuring infrared absorption spectrum, for example. As a specific example, the following method can be cited: (1) IR absorption measurement of the measurement object is performed, (2) thereafter, the measurement object portion (surface layer) of the measurement object is scraped off and further IR absorption measurement is performed, and (3) based on the difference between the measured values before and after the scraping treatment of the obtained surface layer, the concentration of the scraped portion (surface layer) is calculated.

The concentration of fluorine contained in quartz glass can be measured by, for example, ion chromatography, EPMA (Electron Probe Micro-Analysis), fluorescent X-ray spectroscopy, SIMS (Secondary Ion Mass Spectrometry), and the like.

Fig. 2A is a schematic cross-sectional view of the excimer lamp 1 of Fig. 1 cut along the X-Z plane. However, in Fig. 2A, the base (31, 32) is omitted from illustration.

As shown in Fig. 1 and Fig. 2A, the excimer lamp 1 of the present embodiment is configured to emit ultraviolet light L1 in the Z direction with the X direction as the longitudinal direction. A discharge space 11 in which a luminescent gas is sealed is formed inside a discharge capacitor 10.

The excimer lamp 1 has a pair of electrodes (21, 22) for applying a discharge voltage to the discharge space 11. More specifically, the excimer lamp 1 of the present embodiment has an electrode 21 formed on the outer wall of the +Z side of the discharge capacitor 10 and an electrode 22 formed on the -Z side. In this example, the electrodes 21 and 22 are both in a grid shape, and the ultraviolet light L1 is emitted through the gaps between the electrodes 21 and the gaps between the electrodes 22. It is preferable that the electrodes 21 and 22 are both made of a material with high corrosion resistance such as gold (Au). Furthermore, the electrodes 21 and 22 may be in a shape in which a plurality of lines are separated and arranged.

In addition, as shown in FIG2B, the electrode 22 may be formed into a film shape. In this case, as shown in FIG2B, when the excimer lamp 1 is intended to emit ultraviolet light L1 in the +Z direction, it is preferable that the electrode 22 is formed of a material containing a metal that shows reflectivity to the ultraviolet light L1. As an example of a material with high corrosion resistance, the above-mentioned gold shows high reflectivity to the ultraviolet light L1, and therefore can also be used as the material of the electrode 22 in FIG2B.

Furthermore, when it is planned to emit the ultraviolet rays L1 not only in the +Z direction but also in the -Z direction, the electrode 22 on the -Z side may be formed in a grid shape or a line shape.

FIG. 1 corresponds to a plan view of the excimer lamp 1 as viewed from the +Z side, and therefore, the electrode 22 disposed on the -Z side of the discharge capacitor 10 is not shown.

A luminescent gas that forms excimers by discharge is sealed inside the discharge capacitor 10. The luminescent gas is arbitrary, and for example, a luminescent gas whose main component is xenon (Xe) can be used. When a high-frequency AC voltage of about 1 kHz to 5 MHz is applied between the electrode 21 and the electrode 22, the voltage is applied to the luminescent gas via the discharge capacitor 10, and plasma is generated in the discharge space 11. Thereby, the atoms of the luminescent gas are excited to become a quasi-molecular state, and the atoms generate excimer luminescence when they transition to the ground state. When a gas containing the above-mentioned xenon (Xe) is used as the luminescent gas, ultraviolet light L1 with a peak wavelength of about 172 nm can be obtained by the excimer luminescence. Furthermore, by using different substances as the luminescent gas, the wavelength of the ultraviolet light L1 can be changed. Combinations of luminescent gases and peak wavelengths include ArBr (165nm), ArF (193nm), KrBr (207nm), and KrCl (222nm).

As described above, by applying a voltage between the electrode 21 and the electrode 22, the luminescent gas in the discharge space 11 performs excimer luminescence and emits ultraviolet light L1. Therefore, the excimer lamp 1 emits light more strongly in the region where the electrode 21 and the electrode 22 face each other in the discharge space 11. Furthermore, as shown in FIG. 2A, when both the electrode 21 and the electrode 22 are arranged in a grid shape, the excimer lamp 1 emits light more strongly in the region where the arrangement region of the electrode 21 in the outer wall on the +Z side of the discharge capacitor 10 and the arrangement region of the electrode 22 in the outer wall on the -Z side of the discharge capacitor 10 face each other in the discharge space 11.

In this specification, the region that emits light relatively strongly in the discharge space 11 is referred to as an "effective light emission region". More specifically, the effective light emission region refers to a region that emits light that is 60% or more of the peak value in the light intensity distribution along the long side direction (X direction) of the discharge capacitor in the discharge space 11. In each of the figures below FIG. 2A, the symbol 5 is used to represent the effective light emission region.

The excimer lamp 1 has the following characteristics regarding the virtual temperature of each location in the long side direction (X direction) of the discharge capacitor 10. This point is explained with reference to FIG3. FIG3 corresponds to a top view of the excimer lamp 1 illustrated in the same manner as FIG1, with an effective light emitting area 5 and a measurement location (4, 4, ...) added. The description of the measurement location (4, 4, ...) is described later.

The measurement positions (4, 4, ...) are positions for measuring the virtual temperature of the discharge capacitor 10. Specifically, the measurement positions (4, 4, ...) are positions obtained by substantially equally dividing the region within the effective light emitting region 5 of the discharge capacitor 10 into a predetermined number of positions in the longitudinal direction (X direction). In the example of FIG. 3 , the region within the effective light emitting region 5 of the discharge capacitor 10 is substantially divided into four equal parts in the X direction, and a total of five measurement positions (4, 4, ...) are shown. The positions of the X coordinates of the respective measurement positions (4, 4, ...) correspond to X1, X2, X3, X4, and X5. In the example of FIG. 3 , the measurement positions 4 corresponding to the positions X1 and X5 correspond to "a pair of end positions", and the measurement positions 4 corresponding to the positions X2, X3, and X4 correspond to "a middle position".

The measurement locations (4, 4, ...) are provided to measure the degree of variation (uniformity) of the virtual temperature of the discharge capacitor 10 in the longitudinal direction (X direction). Therefore, if the plurality of measurement locations (4, 4, ...) are biased toward the end on the -X side or the end on the +X side, or toward the center in the X direction, the verification of the variation of the virtual temperature of the discharge capacitor 10 in the X direction cannot be said to be effective.

That is, in this specification, "substantially equally divided" means that the temperature is dispersed in the X direction to such an extent that the deviation of the virtual temperature in the X direction of the discharge capacitor 10 can be verified, and within the range of achieving this purpose, the separation distances between the measurement locations (4, 4, ...) are allowed to vary. As an example, the maximum value of the separation distances between the measurement locations (4, 4, ...) is not more than twice the average value of the separation distances.

In the discharge capacitor 10 included in the excimer lamp 1, the virtual temperature T [°C] of each measurement location (4, 4, ...) set as described above and the median value Ta [°C] of all virtual temperatures T satisfy the following equations (1) and (2).

In other words, each virtual temperature T[°C] and the median value Ta[°C] of all virtual temperatures T are in a relationship located within the jumbled region of the graph of FIG. 4 .

The virtual temperature T of each measurement location (4, 4, ...) can be obtained by infrared absorption spectroscopy or Raman spectroscopy.

Infrared absorption spectroscopy is a method for calculating the virtual temperature of silica glass from the shift of the peak (near 2260 cm ^-1 ) representing the stretching vibration of Si-O bonds in silica glass. Specifically, there is a known method for calculating the virtual temperature T _f from the peak wave number ν2 [cm ^-1 ] by simple calculation based on the following formula (3).

Raman spectroscopy is a method that utilizes the shift of the ω ₁ (peak appearing near 440 cm ^-1 ) line caused by the angular vibration of Si-O-Si bonds in silica glass. Specifically, there is a known method for calculating the virtual temperature T _f from the peak position of ω ₁ appearing in the Raman signal of silica glass by simple calculation based on the following formula (4).

The virtual temperature T of each measurement location (4, 4, ...) is measured using the above-mentioned infrared absorption spectroscopy, Raman spectroscopy, etc. Hereinafter, the virtual temperature of each position Xi (i=1, 2, ...) of each measurement location (4, 4, ...) is denoted as Ti.

The median value Ta is a value located exactly in the middle between the maximum value and the minimum value of the virtual temperature Ti at each position Xi.

As described above, when an excimer lamp is manufactured for industrial use, the virtual temperature of the discharge capacitor inevitably varies. On the other hand, when manufacturing the discharge capacitor, the heating and cooling curves are set so that the virtual temperature becomes a certain target value. That is, when the virtual temperature of each measurement location of the discharge capacitor manufactured by the usual method is measured, the value of the virtual temperature used as the target during manufacturing is roughly consistent with the median value of the virtual temperature of each measurement location, and a tendency is shown to fluctuate up and down depending on the measurement location based on the median value.

The graph in Fig. 4 means that the permissible range of the virtual temperature deviation at each measurement location (4, 4, ...) changes according to the virtual temperature median value Ta, in other words, the virtual temperature value (target value) used as the target during manufacturing. Specific numerical examples are listed below. When the virtual temperature median value Ta (i.e., target value) is 920°C, all virtual temperatures Ti at each location Xi are within the range of 823.3°C to 1016.7°C, and the permissible variation is 193.4°C. As another example, when the median value Ta (i.e., target value) of the virtual temperature is 960°C, all virtual temperatures Ti at each position Xi are within the range of 899.3°C to 1020.7°C, and the allowable variation range is 121.4°C. As another example, when the median value Ta (i.e., target value) of the virtual temperature is 980°C, all virtual temperatures Ti at each position Xi are within the range of 937.3°C to 1022.7°C, and the allowable variation range is 85.4°C.

That is, as the median value Ta of the virtual temperature approaches 1000°C, the permissible variation range of the virtual temperature Ti of each measuring position (4, 4, ...) becomes smaller. When the virtual temperature Ti of each measuring position (4, 4, ...) deviates to a degree exceeding the permissible variation range, the illuminance maintenance rate after the excimer lamp is lit for a long time will have a large deviation. In contrast, as in the excimer lamp 1 of the present embodiment, when the permissible variation range of the virtual temperature Ti of each measuring position (4, 4, ...) is controlled within the shaded area in the graph of FIG. 4, the difference in the illuminance maintenance rate of each location after 3000 hours can be controlled to be less than 15%. This will be discussed in more detail later.

Samples #1 to #3 of ideal excimer lamps that suppress the deviation of virtual temperature Ti at each location in the X direction are prepared. These samples #1 to #3 are all excimer lamps with a peak wavelength of 172 nm, in which Xe gas is sealed in a discharge capacitor as a light-emitting gas.

These samples #1 to #3 are manufactured by heating under high-precision control along a carefully set temperature curve during manufacturing, and cooling extremely slowly, which is not a very efficient time spent on manufacturing industrial excimer lamps. Samples #1 to #3 are lamps manufactured with different target virtual temperatures (target values). The target virtual temperatures of each sample #1 to #3 are shown in Table 1 below.

Furthermore, for the sake of caution, the virtual temperature Ti of each measurement location (4, 4, ...) of the samples #1 to #3 was measured. The results confirmed that in any sample #1 to #3, the virtual temperature Ti converged within the range of ±5°C relative to the target value (i.e., the median value Ta).

The time variation of the illuminance maintenance rate of the samples #1 to #3 was measured. Specifically, after being illuminated for a predetermined time, the illuminance of the ultraviolet light from each sample #1 to #3 was measured by illuminance measurement, and the relative value relative to the initial illuminance was calculated. When measuring the illuminance, an ultraviolet integrating light meter (UIT-250) and a separate photoreceiver (VUV-S172) manufactured by Ushio Electric Co., Ltd. were used. The relationship between the illuminance maintenance rate and the lighting time of each sample #1 to #3 was obtained as shown in Figure 5. Furthermore, the results obtained in Figure 5 were redrawn by expressing the horizontal axis in logarithmic terms. The graph is shown in Figure 6.

The linear regression model is used to linearly approximate the data obtained in Figure 6, thereby deriving the relationship between the illuminance maintenance rate y and the lighting time [Log(h)]x in each sample #1~#3. The linear approximation formulas and the determination coefficient R2 are as follows.

Sample #1: Linear approximation y=-4.2999×x+100, coefficient of determination R ² =0.8931 Sample #2: Linear approximation y=-4.9565×x+100, coefficient of determination R ² =0.8998 Sample #3: Linear approximation y=-7.6343×x+100, coefficient of determination R ² =0.9541

In any of samples #1 to #3, since the value of the coefficient of determination of the approximate formula is close to 1, it can be understood that the correlation between the approximate formula and the obtained data is high.

Next, the relationship between the virtual temperature of each sample #1 to #3 (which is the target value and the median value Ta) and the slope of the linear approximation formula is plotted. This graph is shown in FIG7. Hereinafter, the slope of the linear approximation formula is referred to as the "illuminance maintenance rate reduction coefficient", which corresponds to the "coefficient" recorded on the vertical axis of the graph of FIG7.

From the results of FIG. 7 , it can be seen that the degree of change in the illuminance maintenance factor reduction coefficient between the sample #1 with a virtual temperature of 949°C and the sample #2 with a virtual temperature of 987°C is greater than the difference in the illuminance maintenance factor reduction coefficient between the sample #2 with a virtual temperature of 987°C and the sample #3 with a virtual temperature of 997°C. According to the results of FIG. 7 , the relationship between the virtual temperature and the illuminance maintenance factor reduction coefficient is approximated by two straight lines m1 and m2. That is, it can be seen that within the range of the virtual temperature being below 987°C, between the virtual temperature x and the illuminance maintenance factor reduction coefficient y, the relationship approximated by the straight line m1: y=-0.0159*x+10.786 holds. In addition, it can be seen that in the range of virtual temperature above 987°C, a relationship approximated by the straight line m2: y = -0.2651*x + 256.69 holds between the virtual temperature x and the illuminance maintenance factor reduction coefficient y. That is, the straight lines m1 and m2 are the relationship between the virtual temperature and the illuminance maintenance factor reduction coefficient. Hereinafter, it is simply referred to as "relationship α".

Here, in the excimer lamp 1, the uniformity U [%] of the illuminance maintenance factor at each measurement location (4, 4, ...) is defined by the following formula (5) using the maximum value Imax of the illuminance maintenance factor and the minimum value Imin of the virtual temperature.

As can be seen from the results of Figs. 5 and 6, the higher the virtual temperature of the discharge capacitor, the lower the value of the illuminance maintenance factor. That is, when the illuminance maintenance factor of the excimer lamp is measured for each location of the discharge capacitor, the virtual temperature of the location showing the maximum value Imax of the illuminance maintenance factor, in other words, the lowest virtual temperature T1, is defined by T1=x-a when the median value (target value) of the virtual temperature is set to x and the temperature difference between the median value and the location is set to a. Conversely, the virtual temperature of the location showing the minimum value Imin of the illuminance maintenance factor, in other words, the highest virtual temperature T2, is defined by T2=x+a.

When the coefficient of the above relational expression α at the position of the lowest virtual temperature T1 is k1, the intercept is k1′, and the lighting time is τ [h], the illuminance maintenance factor Imax of the portion representing the virtual temperature T1 is defined by the following equation (6).

Similarly, when the coefficient of the above relationship α at the position of the highest virtual temperature T2 is set to k2, the intercept is k2', and the lighting time is τ [h], the illumination maintenance rate Imin of the portion representing the virtual temperature T2 is defined by the following formula (7).

When the above equations (6) and (7) are substituted into equation (5) and transformed into a mathematical formula for calculating the temperature difference a of the virtual temperature relative to the median value, the following equation (8) is obtained.

In an excimer lamp, if the difference in the illumination maintenance rate of each location of the discharge capacitor 10 after lighting for 3000 hours is controlled to be less than 15%, the obstacle in use is low. Therefore, in the above formula (8), τ=3000 and U=15 are substituted.

In addition, the coefficient k1 and intercept k1' of the above-mentioned relationship α at the position of the lowest virtual temperature T1, and the coefficient k2 and intercept k2' of the above-mentioned relationship a at the position of the highest virtual temperature T2 are all based on the relationship a shown in Figure 7 and are uniquely determined according to the value of the virtual temperature.

That is, the target virtual temperature (median value) x is changed in sequence to obtain the allowable temperature difference a, and the allowable upper limit value and the allowable lower limit value are calculated by calculation. The calculation process is shown in Table 2 below.

The relationship between the intermediate value x and the allowable lower limit value (x-a) and the relationship between the intermediate value x and the allowable upper limit value (x+a) obtained in this way are graphed, and the area included in the range of the two is shaded to form the graph of Figure 4. Therefore, by manufacturing the excimer lamp 1 in such a way that the intermediate value Ta of the virtual temperature and the virtual temperature Ti of each measurement position exist in the shaded area shown in Figure 4, the difference in the illuminance maintenance rate of each location of the discharge capacitor 10 after lighting for 3000 hours can be suppressed to less than 15%.

The following describes the results of verification using the embodiments and comparative examples.

(Example 1) Using fluorine-doped quartz glass, a target value of the virtual temperature was set to 983°C under a certain temperature curve, and a plurality of samples of excimer lamps 1 were prepared as Example 1. For one of the plurality of samples prepared, the virtual temperatures of five measuring locations (X1, X2, ..., X5) were measured as shown schematically in FIG3. Specifically, the measurement was performed by the following method. First, a glass chip was obtained by crushing the above five locations located in the effective light-emitting area 5 of the discharge capacitor 10. Then, after measuring the infrared absorption spectrum of the obtained glass chip by the projection method, the calculation based on the above formula (3) was performed. The value obtained by calculation is used as the virtual temperature Ti (i=1, 2, ..., 5) of the measurement location (X1, X2, ..., X5) corresponding to each small piece.

In Example 1, the relationship of the above formula (2) holds true between the virtual temperature T at each measurement location and the median value Ta of the virtual temperature.

Next, the undamaged sample of the excimer lamp 1 of Example 1 was continuously illuminated for 3000 hours. Then, the illuminance maintenance rate of each measurement position (X1, X2, ..., X5) after the illumination for 3000 hours was measured.

FIG8 is a diagram schematically showing a method for measuring the illuminance maintenance rate at each measurement location. Specifically, for the excimer lamp 1 after being lit for 3000 hours, the light meter 41 is set near each measurement location (X1, X2, ..., X5) and adjusted so that only the ultraviolet light L1 at that location is received. Then, by calculating the ratio of the illuminance measured at each location to the initial illuminance, the illuminance maintenance rate at each measurement location (X1, X2, ..., X5) is calculated. During the measurement, as described above, an ultraviolet integrating light meter (UIT-250) and a separate photoreceiver (VUV-S172) manufactured by Ushio Electric Co., Ltd. are used.

(Comparative Example 1) Verification was performed in the same manner as in Example 1, except that the target value of the virtual temperature was set to 983°C as in Example 1 and the temperature curve during manufacturing was changed compared to that in Example 1. In Comparative Example 1, the relationship of the above formula (2) does not hold between the virtual temperature T at each measurement location and the median value Ta of the virtual temperature.

(Example 2) Verification was performed in the same manner as in Example 1, except that the target value of the virtual temperature was set to 909°C and the temperature curve during manufacturing was changed compared to Example 1. In Example 2, the relationship of the above formula (2) also holds between the virtual temperature T at each measurement location and the median value Ta of the virtual temperature.

(Comparative Example 2) Verification was performed in the same manner as in Example 2, except that the target value of the virtual temperature was set to 909°C as in Example 2 and the temperature curve during manufacturing was changed compared to Example 2. In Comparative Example 2, the relationship of the above formula (2) does not hold between the virtual temperature T at each measurement location and the median value Ta of the virtual temperature.

The verification results are shown in the following Table 3 and Figures 9A to 12B. The uniformity in the following Table 3 is a value calculated based on the above formula (5).

According to the above results, in Example 1 and Example 2, in which the virtual temperature Ti (i=1, 2, ..., 5) of each measurement location (X1, X2, ..., X5) is suppressed within the allowable range, the uniformity (degree of deviation) of the illuminance maintenance rate after 3000 hours of lighting is less than 6%, which is significantly lower than the allowable range of 15%. In contrast, in Comparative Example 1 and Comparative Example 2, in which a portion of the virtual temperature Ti (i=1, 2, ..., 5) of each measurement location (X1, X2, ..., X5) exceeds the allowable range, the uniformity (degree of deviation) of the illuminance maintenance rate after 3000 hours of lighting exceeds 15%.

In addition, in the present invention, the shape of the discharge capacitor 10 provided in the excimer lamp 1 is not limited. For example, the discharge capacitor 10 may also have a double tube structure including an outer tube and an inner tube disposed inside the outer tube, and the outer tube and the inner tube are sealed at both ends in the tube axis direction. In this structure, in the excimer lamp 1, the space sandwiched by the inner tube and the outer tube forms a discharge space 11, and the luminescent gas is sealed in the discharge space 11.

1: Excimer lamp 4: Measurement site 5: Effective luminous area 10: Discharge capacitor 11: Discharge space 21: Electrode 22: Electrode 31: Base 32: Base 41: Light meter L1: Ultraviolet light X1: X-coordinate position of the measurement site X2: X-coordinate position of the measurement site X3: X-coordinate position of the measurement site X4: X-coordinate position of the measurement site X5: X-coordinate position of the measurement site

[FIG. 1] A schematic top view showing the structure of one embodiment of the excimer lamp of the present invention. [FIG. 2A] Another schematic cross-sectional view of the excimer lamp of FIG. 1 cut along the X-Z plane, omitting the base. [FIG. 2B] Another schematic cross-sectional view of the excimer lamp of FIG. 1 cut along the X-Z plane, omitting the base. [FIG. 3] A diagram of the effective luminous area and the measurement site attached to the top view of the excimer lamp shown in FIG. 1. [FIG. 4] A graph for explaining the contents of equations (1) and (2). [FIG. 5] A graph showing the relationship between the illuminance maintenance rate and the lighting time of each lamp sample #1 to #3. [FIG. 6] A graph showing the horizontal axis of the graph of FIG. 5 in logarithmic terms. [Fig. 7] A graph showing the relationship between the virtual temperature of each lamp sample #1 to #3 and the slope of the linear approximation. [Fig. 8] A graph schematically showing a method for measuring the illuminance maintenance rate of the excimer lamp at each measurement location. [Fig. 9A] A graph showing the value of the virtual temperature at each measurement location in the excimer lamp of Example 1. [Fig. 9B] A graph showing the value of the illuminance maintenance rate at each measurement location in the excimer lamp of Example 1. [Fig. 10A] A graph showing the value of the virtual temperature at each measurement location in the excimer lamp of Comparative Example 1. [Fig. 10B] A graph showing the value of the illuminance maintenance rate at each measurement location in the excimer lamp of Comparative Example 1. [FIG. 11A] A graph showing the value of the virtual temperature of each measurement site in the excimer lamp of Example 2. [FIG. 11B] A graph showing the value of the illuminance maintenance rate of each measurement site in the excimer lamp of Example 1. [FIG. 12A] A graph showing the value of the virtual temperature of each measurement site in the excimer lamp of Comparative Example 2. [FIG. 12B] A graph showing the value of the illuminance maintenance rate of each measurement site in the excimer lamp of Comparative Example 2.

Claims (3)

An excimer lamp is characterized by comprising: a long strip-shaped discharge capacitor comprising fluorine-doped quartz glass and sealing a luminescent gas therein; and a pair of electrodes for applying a discharge voltage to the interior of the discharge capacitor; wherein within an effective luminescent region of the discharge capacitor, the virtual temperature T[°C] of each measuring portion consisting of a pair of end portions in the longitudinal direction and a plurality of intermediate portions obtained by substantially equally dividing the region between the pair of end portions in the longitudinal direction by a predetermined number satisfies the following equations (1) and (2) when the median value of the virtual temperature T[°C] of each measuring portion is set to Ta[°C], The excimer lamp as described in claim 1, wherein the maximum value and the minimum value of the aforementioned virtual temperature T at each measurement location differ by more than 10°C. An excimer lamp as described in claim 1 or 2, wherein the length of the discharge capacitor in the longitudinal direction exceeds 1 m.

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