JP2006013232A - Method of reproducing laser chamber of ultraviolet gas laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which the laser chamber of an ultraviolet gas laser device can be reproduced easily in a short time by omitting the labor of cleaning/removing dust generated in the laser chamber. <P>SOLUTION: At the time of opening the laser chamber of the ultraviolet gas laser device to the atmosphere for exchanging a consumable component, the accumulated dust in the chamber is prevented from absorbing water by adjusting the dew-point temperature in the working environment to ≤-20°C or, after the consumable component is exchanged and the chamber is isolated from the atmosphere, the water absorbed by the accumulated dust while the chamber is opened to the atmosphere is discharged from the inside of the chamber by performing a dust dehydrating process by introducing a fluorine gas into the chamber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for regenerating a laser chamber used in an ultraviolet gas laser apparatus that oscillates in the ultraviolet region, such as an excimer laser or an F ₂ molecular laser.

In laser chambers used in discharge-excited gas laser devices that emit light in the ultraviolet wavelength region, such as excimer lasers typified by KrF excimer lasers, ArF excimer lasers, and F ₂ molecular lasers, laser medium gases (eg, Ar, Ne, Xe , He, F ₂ , Cl ₂ ) at a pressure of several thousand hPa, a high voltage of several tens of kV is applied between the main electrodes arranged facing each other at intervals of several mm to several tens of mm, By discharging, the laser medium is rapidly excited to the laser upper level, and laser pulse emission is obtained.

  Among them, in a gas laser device used in the field of semiconductor lithography, the repetition frequency of laser emission is as high as several kHz, and pulse discharge is repeated billions of times. Therefore, as shown in Patent Document 1 described later, metal fine particles are knocked out from the surface of the main electrode by sputtering generated by a high electric field accompanying application of a high voltage, and the main electrode is gradually consumed. The struck fine particles are deposited in the laser chamber while reacting with the active halogen gas in the laser chamber (hereinafter, this fine particle deposit is referred to as dust deposit or simply dust).

  As the main electrode is consumed, the change of the main electrode interval and the non-uniformity of the surface of the main electrode also proceed. When the consumption exceeds a certain level, a predetermined laser performance cannot be obtained. Therefore, for example, when a predetermined laser output cannot be obtained, it is necessary to regenerate (maintain) the gas laser device so that the predetermined laser output is obtained. In that case, the laser chamber with degraded laser performance may be discarded and replaced with a new laser chamber. However, this causes a cost for one laser chamber for each maintenance.

  Therefore, conventionally, the laser chamber whose performance has deteriorated is collected, the consumable parts are replaced with new ones, and the laser chamber is assembled again to recycle the laser chamber. Hereinafter, a series of operations for making a laser chamber whose performance has deteriorated into a state where it can be reused is referred to as “laser chamber regeneration processing”.

  In addition to the main electrode that is replaced every time, consumable parts include a preliminary ionization electrode for preliminary ionization, a heat exchanger for adjusting the temperature of the laser chamber, and a gas circulation for constantly feeding fresh gas between the main electrodes. There are a fan for use and its fan bearing, a dust filter for collecting dust generated from the surface of the main electrode, a window for taking out laser light from the laser chamber, etc., and these are replaced with new ones in consideration of the degree of deterioration.

  By the way, most of the generated dust is collected by the dust filter, but a part of the dust is accumulated on the inner wall of the laser chamber and the components in the laser chamber. In particular, a relatively large amount is deposited in a region where the circulating gas flow stays in the laser chamber.

  Since the dust deposit has a large surface area and high hydrophilicity, it can adsorb a large amount of moisture in the atmosphere. Therefore, when the laser chamber is opened to the atmosphere, predetermined parts are replaced, and the atmosphere is shut off again without removing the dust deposit, a large amount of moisture adsorbed on the dust deposit is brought into the laser chamber. “Open to the atmosphere” means that the laser chamber is disassembled and the inside of the laser chamber is exposed to the atmosphere, and “atmosphere cut-off” means that the atmosphere is left in the space inside the laser chamber after the laser chamber is assembled. The component is removed by evacuation and a rare gas such as He or Ne is sealed in the laser chamber.

  As described above, when discharge is performed in a laser chamber containing a large amount of moisture in the dust deposit and laser light emission is repeated, the active halogen gas contained in the laser medium gas is separated from these moisture on the surface of the dust deposit or the space inside the laser chamber. Reacts and decomposes. For example, in the case of fluorine gas, it is decomposed into hydrogen fluoride and oxygen.

  By the way, light in the ultraviolet wavelength region such as an excimer laser absorbs light by an impurity gas such as moisture, hydrogen fluoride, oxygen, and the light emission efficiency is lowered (for example, the upper gas is collided with a laser upper level molecule. The laser output is reduced under the influence of deexcitation that reduces the density of density and the generation efficiency of excited atoms and ions that are precursors of the laser upper level molecules.

  Therefore, it is necessary to eliminate these impurity gases from the laser chamber or prevent them from being generated. For this reason, conventionally, dust deposits in the laser chamber have been cleaned and removed as much as possible during the laser chamber regeneration process.

  FIG. 18 is a conventional laser chamber regeneration processing step diagram.

  In the figure, the laser chamber in which the main electrode is consumed and the laser output is reduced is separated from the ultraviolet gas laser device and collected in the laser chamber regeneration processing chamber. Since this regeneration processing chamber has a negative pressure in the chamber, even if toxic halogen compounds remaining in the laser chamber are scattered, they do not leak out of the chamber. In addition, the harmful substances are safely excluded by the exhaust draft placed side by side.

  In order to replace predetermined parts, the laser chamber is opened to the atmosphere (step S181). The laser chamber has built-in components such as the main electrode, heat exchanger, gas circulation fan, etc. In this state, the dust in the laser chamber cannot be removed sufficiently by hand or with a cleaning tool. All these components are removed and disassembled (step S182) in order to remove dust in the laser chamber as completely as possible and desirably.

  Next, out of the disassembled parts, dust accumulated on the surface of reusable parts and dust accumulated on the inner wall of the laser chamber should be thoroughly wiped with paper or cloth soaked with volatile alcohol. In addition to cleaning / removal, the worn main electrode and parts that are deteriorated over a predetermined level are discarded (step S183). The laser chamber is assembled to the original state using the new replacement part and the durable part from which dust has been cleaned and removed, and then the laser chamber is shut off to the atmosphere (step S184).

Next, the above-described laser chamber cut off from the atmosphere is incorporated in a dummy ultraviolet laser device, and vacuum baking is performed to heat and dehydrate the moisture adsorbed on the inner wall or components of the laser chamber. For example, the entire laser chamber is heated to about 100 ° C., and the degree of vacuum in the laser chamber is maintained at 10 ⁻² Pa or less with a turbo molecular pump or the like, and evacuation is continuously performed for two days or more (step S185).

  Next, discharge passivation of the newly replaced main electrode is performed by sealing the discharge gas mixed with fluorine gas into the laser chamber (step S186). This is because in order to obtain a stable laser output, it is necessary to repeat the discharge a predetermined number of times or more to make the electrode surface uniform. Note that, by performing discharge passivation, a part of the laser chamber is heated to a high temperature of 100 ° C. or higher, so that moisture or the like having high adsorption energy that cannot be removed by the previous vacuum baking can be removed. In addition, since fluorine gas is mixed in the discharge gas, the surface of the new replacement part is made into a fluorinated non-moving body by discharge passivation. By performing this fluorination immobilization treatment, it is possible to suppress a small amount of fluorine gas that is a laser medium from reacting with the surface of the replacement part in a discharge that is performed for laser oscillation later, Therefore, stable laser performance can be obtained for a long time.

Finally, the laser performance is confirmed and adjusted (step S187). Here, it is confirmed whether the laser chamber that has undergone a series of regeneration processing steps has returned to a predetermined performance. For example, if the laser is used for semiconductor lithography, the performance here includes spectral line width, spectral purity, beam shape, beam divergence angle, center wavelength, pulse stability of each value, etc. in addition to laser output. It refers to all the necessary characteristics for each application / use.
JP-A-4-101476 (2nd line to the 7th page, 2nd line from the bottom of page 5)

  However, the conventional laser chamber regeneration processing method has the following problems.

  As described above, accumulated dust is cleaned and removed using paper or cloth containing alcohol etc., but in the case of heat exchangers and gas circulation fans, the shape is complicated and the surface area is large. It takes a lot of labor and time to manually wipe off all dust deposits. Further, in order to disassemble all the components in the laser chamber, it is necessary to remove all sealing materials and screws such as O-rings and gaskets, which also takes a lot of time and effort. Of course, reassembly of parts performed after cleaning also takes time and effort similar to the above disassembly work. According to our data, the disassembly, cleaning and reassembly takes approximately 45 hours.

  Note that the seal material needs to be replaced with a new one because there is a possibility that gas leakage may occur when it is reused. Also, since screw parts such as screws, washers and nuts are small and many, it is difficult to manage the history of how many times they have been used. Normally, when reassembling components, all parts are replaced with new ones. The

  Further, the vacuum baking requires about 40 hours and the discharge passivation requires about 50 hours. Including other laser performance confirmation, a total of 140 hours or more is spent on a series of laser chamber regeneration processes.

Furthermore, when dust is removed using, for example, paper or cloth containing alcohol, the moisture in the atmosphere is trapped in the dust-cleaned / removed surface by the heat of vaporization when alcohol is vaporized. There is a problem. Moisture taken into the surface becomes a source of HF and O ₂ impurity gases that deteriorate the laser performance, and when these impurity gases are generated, the laser output is reduced. Moreover, a part of the alcohol itself used for cleaning may be taken in and remain on the surface. Alcohol becomes a source of CF ₄ , CO ₂ , and CO as impurity gases, and these deteriorate the laser performance and lower the laser output.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a laser chamber regeneration processing method that can save the trouble of cleaning and removing dust generated in the laser chamber.

  In order to achieve the above object, in the first aspect of the present invention, the laser chamber is opened until the laser chamber is opened to the atmosphere, predetermined parts in the laser chamber are replaced, and the laser chamber is shut off to the atmosphere. Is characterized by being kept in a dry atmospheric environment.

  A second invention is characterized in that, in the first invention, a dew point temperature of the dried atmospheric environment is −20 ° C. or lower.

  According to a third aspect of the present invention, the laser chamber is opened to the atmosphere, a predetermined product in the laser chamber is replaced, and the laser chamber is shut off to the atmosphere, and then a mixed gas containing a halogen gas or a halide is flown into the laser chamber. It is characterized by that.

  A fourth invention is characterized in that, in the third invention, the halogen is fluorine.

  A fifth invention is characterized in that, in the third invention, the temperature in the laser chamber is 110 ° C. or higher.

  A sixth invention is characterized in that the regeneration process described in the third invention is performed on the laser chamber which is shut off to the atmosphere described in the first invention.

  A seventh aspect of the invention is characterized in that the regeneration process described in the fifth aspect is performed on the laser chamber cut off from the atmosphere described in the first aspect.

  According to an eighth aspect of the present invention, a predetermined replacement module is prepared before the laser chamber is opened to the atmosphere, the laser chamber is opened to the atmosphere, and the predetermined module in the laser chamber and the replacement module are replaced in module units. The laser chamber is shielded from the atmosphere.

  The ninth invention is characterized in that, in the eighth invention, the laser chamber is maintained in a dry atmospheric environment from when the laser chamber is opened to the atmosphere until the laser chamber is shut off to the atmosphere.

  According to a tenth aspect, in the eighth aspect, the replacement module is subjected to vacuum degassing.

  According to an eleventh aspect of the present invention, a predetermined replacement module part that is vacuum degassed in units of parts before opening the laser chamber to the atmosphere is prepared, the laser chamber is opened to the atmosphere, and the predetermined part in the laser chamber is replaced with the predetermined part. It is characterized in that the module part is replaced with a new one and then the laser chamber is shut off to the atmosphere.

  The twelfth invention is characterized in that, in the eleventh invention, the laser chamber is maintained in a dry atmospheric environment from the time when the laser chamber is opened to the atmosphere until the laser chamber is shut off to the atmosphere.

  According to the first invention, as shown in FIGS. 1 and 2, the working environment is dry until the laser chamber is opened to the atmosphere, the components in the laser chamber are replaced, and then the laser chamber is shut off to the atmosphere. In addition, it is possible to prevent moisture from adsorbing to the inner wall of the laser chamber or the surface of the component, particularly dust deposits generated from the main electrode. Therefore, it is possible to shorten the time for dehydrating the adsorbed moisture in the laser chamber by vacuum baking or the like.

  According to the second invention, since the dew point temperature of the working environment shown in FIG. 2 is −20 ° C. or lower, it is possible to more effectively suppress the adsorption of moisture than the first invention, and a laser by subsequent vacuum baking or the like. The time for dehydration of the adsorbed moisture in the chamber can be further greatly shortened.

  According to the third invention, as shown in FIG. 9 and FIG. 10, the introduced active halogen gas reacts with the moisture adsorbed on the dust deposit in the laser chamber and evaporates as a gas. Adsorbed moisture can be easily dehydrated. In addition, it is possible to dehydrate portions that have conventionally been difficult to clean and remove dust by hand. Therefore, laser performance is not deteriorated due to residual moisture in the laser chamber.

  According to the fourth invention, moisture adsorbed in the laser chamber can be effectively dehydrated by the fluorine gas having high reactivity.

  According to the fifth invention, as shown in the data of FIG. 17, the dehydration reactivity can be increased by setting the temperature in the laser chamber to 110 ° C. or higher, so that the moisture adsorbed on the dust deposit can be efficiently removed. Can be dehydrated.

  According to the sixth invention, as shown in FIG. 12, when parts are being replaced, moisture can be prevented from adsorbing to dust deposits in the laser chamber, and after the laser chamber is shut off to the atmosphere, the laser Moisture that has been somewhat taken into the chamber can be dehydrated.

  According to the seventh aspect, the moisture in the laser chamber can be more effectively dehydrated by the dust dehydration process at a high temperature.

  According to the eighth aspect of the invention, as shown in FIG. 5, the replacement modules can be exchanged in a batch, so that the processing time from the release of the laser chamber to the atmosphere can be shortened, and the laser from the atmosphere can be reduced. Water adsorption into the chamber can be suppressed.

  According to the ninth aspect, since the laser chamber is in a dry work environment while the laser chamber is open to the atmosphere, moisture adsorption from the work environment into the laser chamber can be further suppressed.

  According to the tenth invention, since the vacuum degassing process is performed on the replacement module, it can be avoided that the replacement module brings moisture into the laser chamber.

  According to the eleventh aspect, as shown in FIG. 6, it is possible to suppress the introduction of moisture into the laser chamber by exchanging the parts subjected to the vacuum degassing process.

  According to the twelfth invention, as shown in FIG. 7, the working environment from the release to the atmosphere to the blocking of the atmosphere is dry, so that moisture in the atmosphere can be prevented from being adsorbed in the laser chamber during that time. .

  A method for regenerating a laser chamber of an ultraviolet gas laser apparatus according to the present invention will be described below with reference to the drawings.

  First, the experimental background leading to the present invention and the basic principle of the present invention will be described.

  Dust that adsorbs a large amount of moisture is generated by the metal constituting the main electrode being struck into the discharge gas and reacting with the fluorine gas of the laser medium, as described in the above-mentioned Patent Document 1. It was revealed by the present inventors' dust X-ray diffraction analysis that metal fluoride is the main component.

  When this metal fluoride is exposed to the atmosphere, it has a high affinity with water, so it changes to water molecules that collide and adsorb from the atmosphere and hydrates represented by the following chemical reaction formula. It is known to do.

MF ₂ + xH ₂ O → MF ₂ xH ₂ O (1)
However, M is a divalent metal and x is an arbitrary number.

In addition, even if this metal fluoride hydrate tries to remove moisture by heating in nitrogen or a rare gas,
MF ₂・ H ₂ O → MOHF + HF (gas) (2)
MOHF → MO + HF (gas) (3)
These two reactions have been found to ultimately eliminate the oxygen in the form of metal oxides.

On the other hand, the moisture physically adsorbed on the surface of the laser chamber with a relatively weak adsorption energy of 44 to 50 kJ / mol by van der Waals force has a short average stay time of 10 ⁻⁶ to 10 ⁻⁴ seconds, It can be removed by vacuum exhaust such as a rotary pump. However, if the surface is opened to the atmosphere for a long time, the adsorption sites on the surface gradually change to chemical adsorption sites with a strong binding force. In such a case, moisture is adsorbed on the inner surface of the laser chamber with a strong adsorption energy of about 70 to 300 kJ / mol.

The specimen of the SUS316L material was left in the atmosphere for several hours and then measured with a temperature programmed desorption spectrum analyzer to measure the adsorption energy of moisture on the surface of the specimen, which was 180 kJ / mol. This value corresponds to an average dwell time on the surface of 3.4 × 10 ¹⁵ hours at 20 ° C., 4.5 × 10 ⁸ hours at 100 ° C. and 26 hours at 250 ° C., and an enormous amount of time depending on temperature to remove moisture. You can see this.

  The actual chemical adsorption energy of water molecules is not limited to one value as described above, and is often adsorbed on the surface with three or more different adsorption energies. Therefore, the moisture adsorbed in the laser chamber with the respective adsorption energy is desorbed over the respective time and mixed into the gas of the laser medium.

  As described above, if the time of leaving in the atmosphere is about several hours, the adsorbed moisture is almost removed by evacuating at a baking temperature of 250 ° C. or more for 24 hours or more. However, because there are places in the laser chamber where it is difficult to raise the temperature up to 250 ° C, such as joints of dissimilar metals with different temperature expansion coefficients and bearing mechanisms, practically sufficient adsorption moisture can be obtained by vacuum baking. It cannot be removed. Further, as described above, it is not possible to remove oxygen atoms simply by heating the dust hydrate at a high temperature.

  Therefore, in order to solve the above problem, it is only necessary to prevent moisture from being adsorbed in the laser chamber when the laser chamber is opened to the atmosphere.

However, it is difficult to completely block moisture, and it is not always necessary to completely block moisture. That is, moisture at a physical adsorption level that can be removed by evacuation using a rotary pump or the like, and adsorbed moisture at a level that can be removed by a vacuum baking process and a discharge passivation process may be acceptable.
Therefore, the present inventors have determined the moisture adsorption amount of the laser chamber when the laser chamber is opened in the atmosphere with the predetermined dew point temperature as a parameter and left for a predetermined time. The dew point temperature refers to a temperature at which moisture contained in the atmosphere starts to form water droplets, and can be measured using a dew point meter.

  FIG. 14 shows the results. In the figure, the horizontal axis indicates four types of dew point temperatures as parameters, and the vertical axis indicates that the laser chamber is opened to the atmosphere at each of the above dew point temperatures for 1 hour, and then vacuumed for 1 hour. After that, a rare gas is sealed in the laser chamber until reaching 3000 hPa, and the moisture concentration (ppm) in the laser chamber when the laser chamber temperature is kept at 50 ° C. for 2 hours is shown.

  When the dew point temperature is −10 ° C., a large amount of moisture adsorbed in the laser chamber during release to the atmosphere is re-released in a large amount in the laser chamber after 2 hours. As the dew point temperature was lowered, the amount of adsorbed water decreased. When the dew point temperature was −30 ° C. or lower, the amount of water re-released was below the detection limit.

  Thus, the laser chamber regeneration process in which moisture is not adsorbed in the laser chamber by keeping the dew point temperature in the working environment low is referred to as dry refabrication (dry refab) in the present invention. In the dry refab according to the present invention, the dust deposits in the laser chamber are basically not cleaned / removed.

FIG. 15 shows a pre-test for a change in laser output after a laser beam is opened to the atmosphere for a predetermined time at a predetermined dew point temperature and dry refabrication is performed, and then the laser chamber is shut off to the atmosphere and vacuum baking and discharge passivation are performed. A comparison with the laser output change is shown. The air release time was 1 hour or 3 hours. In addition, the comparison when the second time is performed following the first time is also shown. The change in laser output here is the amount of decrease in laser output after a predetermined time has elapsed, and as described above, the cause of this decrease is due to the generation of impurity gas.

  As is clear from this figure, when the dew point temperature is −10 ° C., the laser performance does not return to the decrease level before the test even if the discharge passivation is performed, but it is deteriorated by about 70%. When the temperature is 20 ° C., the deterioration of the laser performance after dry refab is not so great. Therefore, it was found that the laser performance before the test can be obtained by performing additional discharge passivation for several hours. Further, when the dew point temperature was −30 ° C. or lower, there was no particular deterioration in laser performance due to dry refab.

  Therefore, by performing component replacement at least in a working environment having a dew point temperature of −20 ° C. or lower, laser performance before laser chamber regeneration processing can be obtained without particularly cleaning and removing dust deposits. It is more desirable to replace parts in a work environment with a dew point temperature of −30 ° C. or lower.

  In addition, if parts are replaced in such an air environment with a low dew point temperature, the amount of moisture adsorbed in the laser chamber is extremely suppressed, so that the vacuum baking process for releasing moisture is unnecessary or shortened compared to the conventional case. It becomes possible.

  As another method for achieving the object of the present invention, even if moisture in the working environment is adsorbed by dust deposits in the laser chamber and constitutes dust and hydrate, the hydrate can be easily formed. It may be possible to remove it.

As described above, a metal fluoride hydrate is finally converted into a metal oxide simply by heating at a high temperature. However, by flowing a mixed gas containing fluorine,
_{MF 2 · H 2 O + F} 2 (gas) → MF 2 + 2HF (gas) + O (gas) (4)
It has become clear through experiments by the inventors that a dehydration reaction occurs. In the case of the above reaction, the decomposed oxygen is released as a gas and can be easily removed by evacuation.

  FIG. 16 shows the result of X-ray diffraction analysis of the dust component after changing the temperature environment and flowing a mixed gas containing 1% fluorine gas to the hydrate of the dust component at a flow rate of 100 sccm for 2 hours.

When the above gas was allowed to flow in a temperature environment of 200 ° C., most of the metal fluoride was detected. Although not shown, no metal oxide was detected. Moreover, it turns out that a hydrate reduces and changes to an anhydride as an environmental temperature rises. From this, it is understood that moisture can be dehydrated from the dust hydrate in the laser chamber by flowing a mixed gas containing fluorine gas into the laser chamber.
Thus, in the present invention, a method of dehydrating the moisture of dust hydrate by flowing a mixed gas containing an active halogen gas such as fluorine into the laser chamber is called “dust dehydration treatment”. The activation energy of the dehydration reaction obtained from the above experimental data was 39 kJ / mol, and its index factor was 7.3.

  FIG. 17 shows the result of calculating the time required to dehydrate 99% or more of moisture from the dust component from the above physical property values. According to the figure, the time required for the dehydration reaction becomes shorter as the environmental temperature of the dust hydrate becomes higher, for example, 46 hours at 110 ° C. and 14 hours at 150 ° C. Therefore, if the above method is used, it is not necessary to take the troubles such as total disassembly of the components in the laser chamber, dust cleaning / removal associated therewith, and subsequent reassembly. It has been found that the moisture in the laser chamber can be removed to a predetermined level or less over time.

  Next, an embodiment based on the above basic principle will be described with reference to the drawings.

  FIG. 1 shows an embodiment of a laser chamber regeneration processing step using the dry refab of the present invention. FIG. 2 shows an equipment layout for performing the dry refab.

  For the convenience of later description, the facility layout will be described first.

In FIG. 2, the air in the dry refab chamber 22 is sent to the dehumidifier 23. The sent air is dehydrated until the dew point temperature set by the dew point meter installed in the dehumidifier 23 is reached. The dehydrated air is sent again to the dry refab chamber 22. A dew point meter is also installed in the dry refab chamber 22, and the dehumidifier 23 is feedback-controlled so that the room has a predetermined dew point temperature.
For ensuring safety against toxic gases, the exhaust pump 25 is always operated by the vacuum pump 24 to make the dry refab chamber 22 have a negative pressure, so that external air constantly enters the dry refab chamber 22. For this reason, it is preferable to increase the flow rate of the dehumidifier 23 by making the dry refab chamber 22 a sealed structure. An assembly chamber 26 is provided in contact with the dry refab chamber 22 so that components can be taken in and out through the component carry-in port 26a as indicated by an arrow 26b. It is preferable that the dry refab front chamber 21 and the assembly chamber 26 are also dehumidified.

  In the first embodiment, the following laser chamber regeneration process is performed using the dry refab facility layout.

  In FIG. 1, the laser chamber 1 whose performance has deteriorated and the laser output has been reduced is separated from the ultraviolet gas laser device, and is collected in the dry refab chamber 22 through the dry refab front chamber 21 through the chamber carry-in path 21a indicated by the arrow. .

(Step S11) The collected laser chamber 1 is opened to the atmosphere, and the regeneration process is started.

(Step S12) A predetermined dry refab process A is performed on the laser chamber 1 opened to the atmosphere.

  FIG. 3 shows an example of the dry refab process A (see FIG. 2).

  The laser chamber 1 is carried into the dry reclaim chamber 22 (step S31), and after confirming that the dew point temperature is a predetermined temperature, the laser chamber 1 is opened to the atmosphere (step S32). At this time, the inside of the laser chamber 1 is exposed to the atmosphere, but since the dew point temperature is set low, the amount of adsorption to dust deposits by moisture in the atmosphere is small. Next, predetermined consumable parts are replaced (step S33), the laser chamber 1 is shut off to the atmosphere again (step S34), and finally, a leak detector is used to check whether there is any leak (step S35). Steps S32 to S34 are the time during which the inside of the laser chamber is exposed to the atmosphere, and the shorter the air exposure time, the better.

(Step S13) The dry refab process A is performed, and the laser chamber 1 in which predetermined consumable parts are replaced proceeds to a vacuum baking process in FIG. This is performed to remove the moisture adsorbed on the replacement part. However, since the amount of moisture brought into the laser chamber 1 is small for the above reason, the vacuum baking can be completed in a short time.

(Step S14) Further, a discharge passivation treatment is performed to stabilize the main electrode.

(Step S15) Finally, the laser performance is confirmed and adjusted.

  The laser chamber 1 that has finished the laser chamber regeneration process through step S15 is supplied as a replacement laser chamber of the ultraviolet gas laser device.

  In order to reduce the time during which the laser chamber is opened to the atmosphere during dry refab, it is desirable that the parts to be replaced be prepared in units of modules that can be replaced easily before the laser chamber is opened to the atmosphere.

  FIG. 4 shows a schematic cross-sectional view of the center portion of the laser chamber 1 cut in a direction perpendicular to the optical axis.

  In the figure, an upper main electrode 2 and a lower main electrode 3 are provided opposite to each other at the center of the laser chamber 1 which is cut off from the atmosphere by the upper chamber 1a and the lower chamber 1b. The main electrode 2 is held by an electrode holder 4, the main electrode 3 is held by an electrode holder 5, and the electrode holder 4 is held by a ceramic plate 6. The ceramic plate 6 also serves to block the opening 1c provided above the upper chamber 1a to the atmosphere.

  In the laser chamber 1, for example, when only the main electrode 2 and the main electrode 3 are to be exchanged, after the laser chamber 1 is opened to the atmosphere, the electrode holders 4 and 5 holding the main electrodes 2 and 3, and the electrode holder 4 The ceramic plate 6 holding the metal must also be disassembled at the same time. For this reason, this disassembling operation and reassembly take time, and the amount of moisture adsorbed in the laser chamber 1 increases accordingly.

In order to avoid this, the part including the parts to be replaced (main electrodes 2 and 3 in this case) may be quickly replaced in units of modules. In the case of FIG. 4, five parts are modularized. That is, the module M1 is a part consisting of the main electrode 2, the electrode holder 4 and the ceramic plate 6, the module M2 is a part consisting of the main electrode 3, the electrode holder 5 and the preionization electrode 7, the module M3 is a part of the heat exchanger, The module M4 is a part composed of a gas circulation fan 8 and a bearing 9, and the module M5 is a part of a dust filter. Each module can be easily attached and detached with a predetermined fixing jig.

  As described above, if the replacement module is prepared before the dry refab, the replacement can be easily performed at the same time and the replacement time can be shortened.

  FIG. 5 shows dry refab processing B in the case where consumable parts are replaced in units of modules.

  The dry refab process B is different from the dry refab process A. Before the laser chamber is opened to the atmosphere in step S52, the replacement module is assembled in step S52a of the sub-process and prepared in the replacement operation in step S53. The replacement module is to be replaced at once. The steps before and after that are the same as in the case of dry refab A.

By the way, since moisture is adsorbed to the replacement parts incorporated in the laser chamber, it is necessary to perform a vacuum baking process on the laser chamber after the dry refab process B. As described above, this vacuum baking process requires about 40 hours at the maximum, and the working efficiency is poor. Therefore, it is desirable to subject the replacement part to vacuum degassing before incorporating it into the laser chamber. The vacuum degassing treatment referred to here is heating at a maximum degree of 400 ° C. for about 24 hours with a degree of vacuum of 10 ⁻⁴ Pa or less, whereby water adsorbed on the replacement part can be efficiently dehydrated.

  FIG. 8 shows the temperature-programmed desorption spectrum of the release gas velocity of an untreated SUS part and a SUS part subjected to vacuum degassing. The horizontal axis is the temperature increase parameter, and the vertical axis is the gas release rate from the SUS part at the time of temperature increase. From the figure, it can be seen that, for example, by performing vacuum degassing at 400 ° C., the amount of adsorbed moisture of the SUS parts after vacuum degassing is reduced. It has also been confirmed that the amount of hydrogen, nitrogen, oxygen, carbon monoxide, and carbon dioxide released from the components is reduced by applying the above treatment.

  FIG. 6 shows another dry refab treatment C of this example. In this processing step, two sub-steps are added to the dry refab processing A. That is, before the laser chamber is opened to the atmosphere in step S62, the replacement part is degassed in advance by a vacuum degasser (step S62a), and the replacement part is assembled into a replacement module (step S62b). Then, the replacement module that has been degassed when the laser chamber is opened to the atmosphere is replaced (step S63). The steps before and after that are the same as in the case of dry refab A.

  By adding the above two processing steps and incorporating a fully dehydrated replacement module into the laser chamber, the time for subsequent vacuum baking can be greatly reduced or the vacuum baking process can be omitted. it can.

  By the way, when the replacement part subjected to the vacuum degassing process is once exposed to the atmosphere, moisture in the atmosphere is adsorbed again. Although the amount of moisture adsorbed is small for a short time, if the replacement part is left in the atmosphere for a long time, the state before the vacuum degassing process is approached. Therefore, it is desirable to store the replacement parts that have been vacuum degassed in a predetermined drying chamber. When assembling the replacement module from the parts, it is desirable to assemble the replacement module in a dry room. In some cases, these parts and modules may be stored in a vacuum pack or a pack filled with an inert gas.

  FIG. 7 shows a dry refab process D when parts are assembled in the drying chamber. In the two sub-processes in the figure, the replacement part that has been vacuum degassed in step S72a is carried into a dry assembly chamber, where the replacement part is assembled (step S72b). Thereafter, the laser chamber is opened to the atmosphere (step S72), and parts are replaced in step S73. The steps before and after that are the same as in the case of dry refab A.

The assembly chamber is provided next to the dry refab chamber 22 as in the above-described assembly chamber 26 of FIG. 2, for example, so that the replacement parts can be directly carried into the dry refab chamber 22 without passing through the atmosphere with much moisture. It is desirable that For the same reason, it is desirable to install a vacuum degassing device, a leak detector, etc. in the dry assembly chamber 26 or the dry refab chamber 22. Further, it is desirable that the dew point temperature of the assembly chamber 26 is −10 ° C. or lower.

  In the dry refab treatment of the present invention, it is more desirable that the dew point temperature be −30 ° C. or lower, and the time during which the laser chamber is opened to the atmosphere is preferably within 3 hours.

  As described above, by performing the dry refab process, the vacuum baking process time can be shortened or omitted, and the laser chamber regeneration process can be completed in a shorter time than before.

  As described above, the moisture adsorbed on the dust deposit in the laser chamber is dehydrated by the dust dehydration process, and the cleaning and removing work of the dust deposit accompanying the laser chamber regeneration process is omitted, thereby shortening the laser chamber regeneration process time. Can also be planned.

  FIG. 9 shows a laser chamber regeneration processing step to which dust dehydration processing is applied as a second embodiment of the present invention.

  The deteriorated laser chamber is transported to the regeneration processing chamber and released into the atmosphere in step S91, and the consumable parts are replaced in step S92. In this case, unlike the case of Example 1, the moisture in the atmosphere does not have to be dehumidified. In addition, in order to shorten the replacement time of parts, it is possible to supply replacement parts by appropriately using the sub-processes described in FIGS. Next, after dust dehydration processing is performed in step S93, discharge passivation is performed immediately in step S94. The subsequent steps after laser performance confirmation / adjustment are the same as those in the first embodiment and will not be described.

  FIG. 10 shows an apparatus configuration diagram for carrying out the dust dehydration process.

  Gas port openings 31 and 32 are formed in the laser chamber 1 apart from each other, and a gas intake port and a gas exhaust port (not shown) are respectively attached to the openings 31 and 32. The gas intake port includes a gas line 33a of a fluorine mixed gas cylinder 33 in which fluorine gas is mixed with a rare gas at a predetermined ratio, and cleaning for removing excess fluorine gas from the laser chamber 1 after dust dehydration processing. The gas lines 34a of the rare gas cylinders 34 are connected in parallel. A mass flow controller (MFC) 35 is attached to the gas line 33a in order to send fluorine gas into the laser chamber 1 by a predetermined flow rate.

  On the other hand, a halogen filter 36 for removing toxic fluorine gas is attached to the gas exhaust port, and a rotary pump 37 for evacuation is disposed. Further, the rotary pump 37 is bypassed via a check valve 38 in order to cause the fluorine gas to flow. Around the laser chamber 1, a heater (not shown) is attached at a predetermined location so that the laser chamber 1 can be heated at a high temperature. The heater is preferably a mantle heater that can be easily detached.

  FIG. 11 shows a dust dehydration process using the above configuration diagram.

(Step S111) The deteriorated laser chamber 1 is evacuated to remove atmospheric components in the chamber 1. The degree of vacuum at this time may be about 10 Pa.

(Step 112) For example, a fluorine mixed gas having a fluorine gas ratio of 1% is introduced into the laser chamber 1 from the fluorine mixed gas cylinder 33 through the MFC 35, and flows so as to reach the inside of the chamber 1. The flow rate of the fluorine mixed gas is desirably 100 sccm or more.

(Step S113) The heater attached to the laser chamber 1 is heated, and after the chamber 1 reaches a predetermined temperature, the temperature is maintained for a certain time.

(Step S114) After the predetermined dust dehydration process is completed, the heater is turned off, the flow of the fluorine mixed gas line 33a is stopped, and the inside of the laser chamber 1 is evacuated by the rotary pump 37.

(Step S115) Finally, the rare gas in the rare gas cylinder 34 is sealed in the laser chamber 1 to finish the dust dehydration process.

  In step 113, the dehydration process may be performed with reference to the data shown in FIG.

  As described above, according to the present invention, the dust dehydration process is performed at the time when the laser chamber is shut off to the atmosphere without performing cleaning / removal of dust deposits in the laser chamber in parallel with the replacement work of the worn parts. By performing the above, moisture adsorbed on the dust deposit in the laser chamber can be removed in a short time and over the details of the component parts. As a result, it is not necessary to disassemble the components, clean and remove dust deposits, and reassemble the components, and the vacuum baking process can be omitted, so that the laser chamber regeneration processing time can be greatly shortened. Furthermore, since the laser chamber can be opened to the atmosphere in a normal atmospheric environment, there is no need to particularly modify the laser chamber regeneration processing chamber.

  In this embodiment, the active gas used for the dust dehydration process has been described as the fluorine gas. However, the present invention is not limited to this, and a halogen gas other than the fluorine gas can be used as appropriate.

  FIG. 12 shows another embodiment of the laser chamber regeneration processing method of the present invention.

  In the case of the present embodiment, after starting the regeneration process in step S121, the dry refab process (step S122) used in the first embodiment is performed, and then the dust dehydration process used in the second embodiment is performed (step S123). Two processing steps effective in removing moisture are combined in succession. Since the two processes and the processes before and after the two processes are obvious, the description thereof is omitted here.

  By the above method, it becomes possible to remove the moisture in the laser chamber in two stages, and it is possible to further suppress the deterioration of the laser performance caused by the moisture. In the case of the present embodiment, for example, even if dry refab treatment is performed at a dew point temperature of −20 ° C. or higher, it is expected that moisture is removed to a level that does not deteriorate laser performance by performing dust dehydration treatment next.

  FIG. 13 shows data comparing laser chamber regeneration processing times according to the prior art and the above three embodiments. As can be seen from the figure, when the laser chamber processing time in the prior art is 100%, it is 62% in the first embodiment and 66% in the second and third embodiments. In addition, the laser chamber regeneration processing time can be significantly shortened compared to the prior art.

  As described above, by using the laser chamber regeneration processing method of the present invention, it is possible to shorten the laser chamber regeneration processing time of the ultraviolet gas laser apparatus.

  According to the laser chamber regeneration processing method of the present invention, the maintenance of the laser chamber of the ultraviolet gas laser device can be facilitated, and the operating rate of the ultraviolet gas laser device can be improved.

It is process drawing for demonstrating Example 1 of this invention. It is a conceptual diagram of the example of an equipment layout used by this invention. It is process drawing for demonstrating the dry refab process A of this invention. It is a cross-sectional schematic diagram for demonstrating the module in this invention. FIG. 5 is a process diagram for explaining a dry refab process B. FIG. 6 is a process diagram for explaining dry refab processing C; FIG. 5 is a process diagram for explaining a dry refab process D; It is a figure which shows the temperature dependence of the discharge gas velocity in SUS material. It is process drawing for demonstrating Example 2 of this invention. It is an apparatus block diagram for performing the dust dehydration process of this invention. It is process drawing for demonstrating a dust dehydration process. It is process drawing for demonstrating Example 3 of this invention. It is a comparison figure of the laser chamber reproduction | regeneration processing time by the method of the past and this invention. It is a figure which shows the relationship between the moisture content discharge | released in a laser chamber, and dew point temperature. It is a figure which shows the relationship between the reduction amount of a laser output, and dew point temperature. It is a figure explaining the dehydration effect by fluorine gas. It is the figure which calculated the relationship between the time for performing dehydration of 99% or more, and heating temperature. It is a figure for demonstrating the conventional laser chamber reproduction | regeneration processing method.

Explanation of symbols

M1 to M5 Module 1 Laser chamber 2, 3 Main electrode 4, 5 Electrode holder 6 Ceramic plate 7 Preionization electrode 8 Gas circulation fan 21 Dry refab front chamber 22 Dry refab chamber 23 Dehumidifier 24 Vacuum pump 25 Exhaust dryer 26 Assembly chamber 33 Fluorine mixed gas cylinder 34 Noble gas cylinder 35 Mass flow controller 36 Halogen filter 37 Rotary pump

Claims (12)

An ultraviolet gas laser characterized in that a laser chamber is opened to the atmosphere, a predetermined part in the laser chamber is replaced, and the laser chamber is kept in a dry atmospheric environment until the laser chamber is shut off to the atmosphere. Laser chamber regeneration processing method of apparatus. The laser chamber regeneration processing method for an ultraviolet gas laser apparatus according to claim 1, wherein a dew point temperature of the dried atmospheric environment is -20 ° C or lower. The laser chamber is opened to the atmosphere, a predetermined product in the laser chamber is replaced, the laser chamber is shut off to the atmosphere, and then a mixed gas containing a halogen gas or a halide gas is allowed to flow into the laser chamber. A laser chamber regeneration processing method for an ultraviolet gas laser apparatus. 4. The laser chamber regeneration processing method for an ultraviolet gas laser device according to claim 3, wherein the halogen is fluorine. 4. The method of claim 3, wherein the temperature in the laser chamber is 110 [deg.] C. or higher. A laser chamber regeneration processing method for an ultraviolet gas laser apparatus, wherein the regeneration process according to claim 3 is performed on the laser chamber cut off from the atmosphere according to claim 1. A laser chamber regeneration processing method for an ultraviolet gas laser apparatus, wherein the regeneration process according to claim 5 is performed on the laser chamber cut off to the atmosphere according to claim 1. A predetermined replacement module is prepared before the laser chamber is opened to the atmosphere, the laser chamber is opened to the atmosphere, the predetermined module in the laser chamber and the replacement module are replaced in units of modules, and the laser chamber is A laser chamber regeneration processing method for an ultraviolet gas laser device, characterized by shielding the atmosphere. 9. The laser of an ultraviolet gas laser device according to claim 8, wherein the laser chamber is maintained in a dry atmospheric environment from when the laser chamber is opened to the atmosphere until the laser chamber is shut off to the atmosphere. Chamber regeneration processing method. 9. The laser chamber regeneration processing method for an ultraviolet gas laser device according to claim 8, wherein the replacement module is subjected to vacuum degassing processing. Prepare predetermined replacement module parts that have been vacuum degassed in units of parts before opening the laser chamber to the atmosphere, open the laser chamber to the atmosphere, and connect the predetermined parts in the laser chamber and the replacement module parts. A laser chamber regeneration processing method for an ultraviolet laser device, characterized in that the laser chamber is replaced and then the laser chamber is shut off to the atmosphere. The laser of the ultraviolet gas laser device according to claim 11, wherein the laser chamber is maintained in a dry atmospheric environment from the time when the laser chamber is opened to the atmosphere until the laser chamber is shut off to the atmosphere. Chamber regeneration processing method.

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