JPH01115182A - Medium gas control apparatus for excimer laser - Google Patents

Abstract

PURPOSE:To allow flowing of normal medium gas by generating pure halogen gas through decomposition of metal halogenide by a halogen adding means, adding such gas to the medium gas within the medium gas circulation system and inserting an impurity removing means in the medium gas circulation system. CONSTITUTION:A halogen adding means 30 generates the pure halogen gas through thermal decomposition or optical decomposition of metal halogenide within a closed housing 31 and adds the gas to the medium gas. As a metal halogenide, a metal fluoride is suitable and it is recommended to use CoF3 or AgF for thermal decomposition and use AgF for optical decomposition. A halogen concentration system 60 controls amoung of halogen generated by controlling thermal decomposition temperature and amount of light tor optical decomposition of halogen adding means 30. An impurity removing means 50 is inserted into the medium gas circulation system 20 to remove impurity including unnecessary halogenide within the medium gas. Thereby, the medium gas not including impurity can be allowed to flow into the excimer laser apparatus.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is an excimer laser medium gas control device suitable for oscillating short-wavelength laser light such as ultraviolet light, which uses a rare gas and 710% as a laser active substance. The present invention relates to a method for controlling the amount or concentration of halogen in a medium gas containing halogen gas and flowing through an excimer laser device.

[Conventional technology]

As mentioned above, an excimer laser is a gas laser device that emits ultraviolet light with a short wavelength of approximately 2,000 people.
*The excimer, which is an excited dimer in which one rare gas atom such as K r + It acts as a seed and amplifies light through stimulated emission, causing laser oscillation. A medium gas prepared by diluting a laser active material such as a rare gas and a halogen with a buffer gas is sent to the laser tube of this excimer laser, and these laser active materials are excited to become an excimer by, for example, electric discharge. However, the halogen in this medium gas is extremely reactive, especially at high temperatures, and easily causes a bonding reaction with the constituent materials of the laser device and some impurities contained in the medium gas within the laser tube, which prevents laser oscillation. With this action, the halogen concentration in the medium gas decreases fairly rapidly, and such a change in the composition of the medium gas generally causes a decrease in laser output.
For this reason, in the excimer, it is necessary to keep a medium gas flowing in the laser tube during excitation of the laser active material or subsequent laser oscillation.

Since impurities generated by halogen bonding reactions have an unfavorable effect on laser oscillation, the easiest way to flow a medium gas that does not contain unnecessary impurities during laser oscillation into the laser tube as described above is to create a new medium. Gas is constantly supplied, but even if the flow rate is lowered to the minimum allowable value, the expensive rare gas contained in the medium gas is wasted and harmful halogen gas is released to the outside. It turns out. Therefore, a so-called circulation type medium gas is used in which the medium gas is circulated through the C-za tube, removing unnecessary impurities from the medium gas, replenishing the medium gas with the halogen gas consumed by the reaction, and returning the medium gas to the laser tube. The supply method has come to be adopted. This I11
According to the method, the consumption of medium gas is reduced to 175 to 1/10 of the conventional method.
In contrast, the lifetime of the medium gas can be extended by 5 to 10 times. New halogen gas for replenishment is taken out from a dedicated cylinder as needed.

[Problem that the invention seeks to solve]

However, halogen gas, especially fluorine gas, cannot be stored in a cylinder in its pure state because it is highly dangerous, so it is stored in a state diluted to a low concentration with the aforementioned buffer gas. Therefore, in order to replenish the medium gas with halogen, it is necessary to replenish not only the halogen but also the buffer gas, and the medium gas corresponding to the amount of buffer gas must be released from the circulation system. Of course, the released medium gas contains rare gas, and the rare gas, that is, the laser active material, is lost, and of course, halogen gas is also released, so harmful gases are released to the outside. Become. Furthermore, since the buffer gas that occupies most of the emitted medium gas is actually a rare gas different from the laser active substance, the rare gas is also wasted in the form of buffer gas. The only way to solve this problem is to stop replenishing the medium gas with halogen gas in diluted form. It is conceivable that electrolysis could be used to generate the required amount of fluorine in supplementary or pure form. However, such electrolyzers are quite cumbersome to operate and have their own dangers; excimer lasers usually use a medium gas of 2 to 3 atmospheres, and the fluorine production must also be carried out at this pressure. , it becomes quite difficult to balance the pressure between the yin and yang regions during electrical separation. Furthermore, since it is electrolysis, if the necessary fluorine gas is generated on the anode side, unnecessary hydrogen gas will also be generated on the cathode side, and if the two gases were to mix, an explosion would occur immediately.

The present invention solves these problems, generates halogen gas in a pure form by simple and safe means, and replenishes the medium gas. It is an object of the present invention to obtain a medium gas control device for an excimer laser that allows flow to flow through an excimer laser device.

Means for Solving Problem c] The present invention provides an excimer laser medium gas 111 that contains rare gas and halogen gas as laser active substances and connects the amount or concentration of halogen in the medium gas that is passed through an excimer laser device. ? II device includes a medium gas circulation system that circulates a medium gas from the outside into a closed loop through an excimer laser device, and a metal halide which is held in a closed container coupled to the medium gas circulation system and whose decomposition generates halogen gas. halogen addition means for generating and adding halogen to the medium gas in the medium gas circulation system; impurity removal means inserted into the medium gas circulation system for removing impurities including unnecessary halogen compounds from the medium gas; By comprising a halogen concentration control system that controls the amount of halogen gas generated by the halogen addition means so that the halogen concentration of the medium gas is set to a predetermined value according to the detected value or estimated value of the halogen concentration, the above-mentioned It has succeeded in achieving its purpose.

[Effect]

The present invention focuses on the fact that metal halides can be used as a halogen generation source, as described in the above structure.
The halogen addition means in the present invention stores a metal halide in a closed container, thermally decomposes or photodecomposes the metal halide, generates halogen in a pure form, and adds the generated halogen to the medium gas.

Metal halides are particularly suitable as metal halides, and for thermal decomposition, CoFs and Age! It is better to use CoFs, and it is better to use AgF for photolysis.
Fluorine can be easily generated from these by heating to 500-700℃, and by heating 8get to a slightly lower temperature, and experiments have shown that fluorine can be easily generated from them by heating them to a temperature slightly lower than this. No metal vaporization is observed in this method, and the fluorine produced is chemically pure. AgF is relatively easily photodecomposed by irradiating it with ultraviolet light at a relatively low temperature, and of course vaporization of the metal does not occur.Also, in the case of thermal decomposition, the heating temperature can be controlled, and in the case of photolysis, the amount of light can be controlled. By doing so, it is possible to control the generation rate of halogen gas, so that halogen gas can be generated at the rate necessary for replenishing the medium gas.

Since the halogen gas generated by the halogen addition means is chemically pure and does not contain any unnecessary substances, adding it to the medium gas will not increase the volume of the medium gas or increase the pressure. Therefore, as mentioned in the above configuration, the medium gas circulation system is closed from the outside as a closed loop, and unlike conventional methods, when adding or replenishing halogen gas, rare gas is not allowed to escape to the outside, or harmful halogen gas is released. You can eliminate the need to do so. However, if the medium gas circulation system is made into a closed loop like this,
If left as is, impurities created by the bonding reaction of halogen gas in the excimer laser device would accumulate in the loop and adversely affect the laser oscillation. Therefore, in the present invention, the impurity removal means in the above configuration is integrated into the medium gas circulation system. to remove impurities including unnecessary halogen compounds from the medium gas. These impurities include solid and gaseous impurities, and it is best to remove fixed or powdered impurities with a filter.The main gaseous impurity is HF.
, No□CF, etc., and can be removed using an adsorbent, but it is easiest and most reliable to use a low-temperature trap cooled with liquid nitrogen, for example.

The halogen concentration control system generates halogen at a desired rate by controlling the thermal decomposition temperature of the halogen addition means and the amount of light for photolysis, but in order to perform this control accurately, the halogen concentration in the medium gas must be controlled as accurately as possible. need to know.

Theoretically, the most accurate method for detecting this halogen concentration is to use a gas analyzer, but in practice it is possible to detect the halogen concentration by using a gas analyzer to detect the laser output. It is usually sufficient and practical to estimate the halogen concentration indirectly from

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. In the following examples, it is assumed that Kr is used as the rare gas and fluorine is used as the halogen as the laser active substance.
It is assumed that Ar is used as the buffer gas. FIG. 1 shows an embodiment in which fluorine is generated by thermal decomposition as the halogen addition means 30.

In FIG. 1, an excimer laser device 10 has a laser tube 11 housed in its housing, both ends of which are closed with transparent windows 12, and a laser resonant system is formed outside these windows 12. A partial reflection mirror 15 and a total reflection mirror 16 are provided. A pair of discharge electrodes 13 are provided on the left and right bulges of the laser tube 11 in the figure, and by discharging between the picture electrodes 13 and 13 using a high-voltage power source 14, Kr contained in the medium gas inside the laser tube is discharged. It is designed to excite fluorine. This excitation causes laser oscillation, and a laser beam LB is output from the partial reflecting mirror 15 toward the left in the figure.

A medium gas port 11a and an outlet 11b are provided at both ends of the laser tube 11, to which piping of a medium gas circulation system 20 is connected. The medium gas circulation system 20 is a closed gas loop consisting of a gas circulation fan 21, some valves, and piping, and a halogen addition means 30 and an impurity removal means 50 are inserted into this loop. The valve 22 is for releasing air when the medium gas circulation system is first filled with medium gas, and is always closed during operation.

The halogen addition means 30 has an electric heating plate 32 and a dish 33 containing a metal halide M)I stored in a closed container 31, and the temperature of the electric heating plate 32 is controlled by an attached temperature controller 34.
Therefore, the temperature of the metal halide Ml in the dish 33 can be accurately controlled. In this example, the closed container 31
has an inlet/outlet so that the medium gas in the medium gas circulation system flows directly inside the closed container 31, but it is also possible to use a common inlet/outlet and connect it to the piping of the medium gas circulation system. The metal halide MW is, for example, CoF.
s, and is heated to 500 to 700°C by the electric heating plate 32. Since such high-temperature parts easily react with fluorine in the medium gas, it is desirable to use monel metal as the material for the electric heating plate 32 and the plate 33.

The impurity removal means 50 consists of a filter 51 and a low-temperature trap, and the low-temperature trap cools the low-temperature container 52 with, for example, liquid nitrogen 54 filled between it and a jacket 53, and the liquid nitrogen is introduced from the inlet 52a. The gaseous impurities in the purified medium gas are condensed, and the purified medium gas is led out from the outlet 52b. The filter 51 removes solid impurities from the medium gas, and the cold trap removes gaseous impurities such as IP, No., CF, etc. As in this example, it is preferable that the impurity removing means 50 be disposed within the medium gas circulation system 20 closest to the inflow point of the a-body gas into the excimer laser device interior 10. Piping 1
Impurities adhering to the valve and the halogen addition means 30 and mixed into the medium gas can be prevented from entering the excimer laser device.

The halogen concentration control system 60 can be composed of, for example, a simple microcomputer, and an operating device 61, such as a keyboard, is connected to its input interface 60a. The signal Sa given to this input interface 60a
is an estimated value of the halogen concentration in the medium gas, and is emitted from the photodetector 62 that receives the laser light from a very small *62a or beam splitter placed in the laser beam LB emitted from the excimer laser device. In this embodiment, the gas analyzer 63 includes a valve 63a on the outlet side of the medium gas from the excimer laser device of the medium gas circulation system 20.
63b, and the detected value Sb of the halogen concentration therefrom is also given to the input interface 60a of the halogen concentration control system 600 microcomputer. However, this halogen detection value sb is used when first filling the laser tube 11 and medium gas circulation system 20 of the excimer laser device with medium gas, and during normal operation, the estimated value Sa is used for halogen control. It is convenient to use the one above. The microcomputer compares this specified value Sa with a reference value set in advance via the operating device 61, and when the specified value Sa cannot be lower than the reference value, outputs the specified temperature value St via its output interface 60b. It is applied to the temperature controller 34 of the halogen addition means 30.

The lower left side of Fig. 1 shows a laser tube 11 and a medium gas circulation system 2.
0 shows cylinders 71 to 73 for medium gas to be filled first. For example, cylinder 71 is for Kr, cylinder 72
The cylinder 73 is for Ar as a buffer gas, and the cylinder 73 is for fluorine diluted with Ar. Each cylinder 71 to 73 has a pressure reducing valve 71.
a to 73a are respectively attached, and flow ffl adjustment valves 74 to 76 are connected to their outlet sides, respectively, and further connected to the medium gas circulation system 20 via a common valve 77. At the time of initial filling of the medium gas, the pressure reducing valves 71a~
73a and the common valve 77 are open, the flow rate adjustment valve 74 is opened.
- 76, an opening command is issued from the halogen concentration control system 60 to send the gas to the medium gas circulation system 20 at a predetermined ratio. The component ratio in the medium gas at this time is, for example, Ar: 96.5
%+ Kr is 3.0% and fluorine is 0.5%. After the initial filling of the medium gas is completed, check the halogen gas concentration using the gas analyzer 63, and then close the valve 77 and the pressure reducing valve 7La.
~ Close all 73a.

As a result, the medium gas circulation system 20 is separated from the initial filling system and becomes a closed loop completely closed from the outside.

In the excimer laser device and its medium gas control device configured as described above, a command is sent to the high voltage power supply 14 of the excimer laser device 10 using the micro combinator of the halogen concentration control system 60, and the medium in the laser tube 11 is controlled. Gas is excited by electric discharge to cause laser oscillation. When the laser active substances are Kr and fluorine as in this example, the wavelength of the laser beam is 2480 nm. The halogen concentration control system 60 sends a detection command DS to the photodetector 62 in synchronization with this laser oscillation.
to read the specified value Sa mentioned above. The control of the fluorine concentration based on this is as described above.

FIG. 2 shows an embodiment in which photodecomposition of a metal halide is used as the halogen addition means 40. Since everything except the halogen addition means in this embodiment is the same as in FIG. 1, only the illustrated halogen addition means 40 will be described below. The main body of this halogen addition means is a closed container 41 with a transparent window 42 made of, for example, calcium fluoride.
A dish 43 on which metal halide Ml is placed is housed under this window. In this embodiment as well, the inlet and outlet of the closed vessel 41 are directly connected to the piping of the medium gas circulation system 20, so that the medium gas flows into the closed vessel 41. As mentioned above, AgF is preferably used as the metal halide MH, and an ultraviolet light fi 44 such as a xenon lamp or a mercury lamp is provided for photodecomposition, and is driven by the lighting circuit 45. The ultraviolet light from the ultraviolet light [44] is focused by a lens 46 onto the metal halide 15 through a window 42, and in this ultraviolet light path there is an aperture 4 controlled by an operator 48.
7 or a slit is provided, and the amount of ultraviolet light passing through the aperture 47 can be controlled by an operating device 48.

As in the previous embodiment, the ring 8 actuator 48 is given a light quantity designation value Go based on the estimated value Sa of the halogen concentration from the microcomputer of the halogen concentration control system 60, and the operating device 4
8 controls the amount of fluorine generated by the halogen addition means 40 by controlling the opening degree of the aperture 47 to match the specified value. An electric heating plate may be provided under 43 to promote photolysis.

The present invention is not limited to the embodiments described above, and the present invention can be implemented in various embodiments. Various types of halogens and metal halides can be selected, and the mode of controlling the halogen concentration can also be modified depending on the situation within the scope of the present invention. In the above embodiment, the buffer gas diluted halogen from the cylinder was used for initial filling of the medium gas into the laser tube and the medium gas circulation system, but halogen was generated from the halogen addition means for initial filling. The temperature specification or light intensity specification value for the halogen addition means, which may be made to
Although the specified values are emitted based on the estimated value of the halogen concentration from 2, it is also possible to emit these specified values based on the detected value of halogen from the gas analyzer. However, in this case, Since impurities contained in the gas may interfere with gas analysis, it is desirable to provide a small impurity removal means similar to that described in the embodiment on the sampling side of the gas to be analyzed.

〔Effect of the invention〕

As explained above, in the present invention, a metal halide is decomposed by a halogen addition means to generate halogen gas in a pure form, and the halogen gas is added to a medium gas in a medium gas circulation system, thereby causing a reaction in a laser tube or the like. Since the consumed halogen component can be replenished without increasing the amount of medium gas, the medium gas circulation system can be made into a closed loop that is completely closed from the outside. Since there is no need to release halogen gas to the outside, the amount of rare gas consumed can be significantly reduced compared to the conventional method, and the release of harmful halogen gas can be eliminated. In addition, since an impurity removal means is inserted in the medium gas circulation system, it removes harmful and useless impurities that may be generated by the operation of the excimer laser device, and returns the excimer laser device to a normal medium containing no impurities. Laser oscillation conditions can be maintained favorably by passing the gas through.

As described above, the present invention makes it possible to automatically control and manage the composition of medium gas using a halogen concentration control system, while reducing operating costs of excimer laser equipment and effectively preventing troubles such as pollution. It is expected that this will contribute to the practical application and further development of excimer laser devices.

[Brief explanation of the drawing]

All figures relate to the present invention, and Figures 1 and 2 show an embodiment of the medium gas control device for excimer laser according to the present invention, which utilizes thermal decomposition and photodecomposition of metal halides, respectively, to generate halogen by means of halogen addition. In Figure 0, which is a configuration diagram, 10: excimer laser device, 11: laser tube, 11a: laser tube inlet, 11b: laser tube outlet, 12: transparent window, 13: discharge electrode, 14: high voltage power source for discharge, 15: partial reflection mirror, 16: total reflection mirror, 20: medium gas circulation system, 21: halogen gas circulation fan, 22
: Release valve, 3o: Metal halide thermal decomposition type halogen addition means, 31: Closed container, 32: Electric heating plate, 33: Dish, 3
4: Temperature controller, 40: Metal halide photodecomposition type halogen addition means, 41: Closed container, 42: Transparent window, 43:
Dish, 44: Ultraviolet light source, 45: Lighting circuit, 46: Condensing lens, 47: Aperture, 48: Aperture operator, 50: Impurity removal means, 51: Filter, 52: Low temperature container for low temperature trap, 52a, 52b + inlet/outlet of low temperature container, 53: Jacquef), 54: liquid nitrogen, 60: halogen concentration control system or micro combinator for it, 60a = microcomputer input interface, 60b; microcomputer output interface, 62: laser output Detection photodetector, 62a: small mirror, 63: gas analyzer,
63a, 63b: Gas detection valve for gas analyzer, 71:
Kr cylinder, 72: Ar cylinder, 73: Ar dilution halogen cylinder, 71a-73b: pressure reducing valve, 74-76
:Flow rate adjustment valve, 77:Valve for initial filling of medium gas, DS:
Detection stirring order, LB: laser beam, MH dimetal halide, Sa: designated value of halogen concentration, Sb: detected value of halogen concentration, T: designated value of light amount for photolysis, St: designated value of temperature for thermal decomposition. L″1JjF: L″No 0 storage − t

Claims (1)

[Scope of Claims] 1) A device for controlling the amount or concentration of halogen in a medium gas containing rare gas and halogen gas as laser active substances and flowing through an excimer laser device, the device controlling the amount or concentration of halogen in a medium gas flowing through an excimer laser device. There is a medium gas circulation system that circulates the metal from the outside into a closed loop, and a metal halide is held in a closed container connected to the medium gas circulation system, and the metal halide is decomposed to generate halogen gas. a halogen addition means for adding halogen to the medium gas; an impurity removal means inserted into the medium gas circulation system for removing impurities including unnecessary halogen compounds from the medium gas; A halogen concentration control system for controlling the amount of halogen gas generated by a halogen adding means so that the halogen concentration of the medium gas is at a predetermined value. 2) In the control device according to claim 1, the halogen addition means generates halogen gas by thermal decomposition of the metal halide, and the halogen concentration control system controls the thermal decomposition temperature of the metal halide of the halogen addition means. A medium gas control device for an excimer laser, characterized in that the medium gas control device is configured to control the medium gas. 3) In the control device according to claim 2, the halogen is fluorine, and the metal halide is CoF.
An excimer laser medium gas control device characterized in that _3 is used. 4) In the control device according to claim 2, the halogen is fluorine, and the metal halide is AgF.
A medium gas control device for an excimer laser, characterized in that _2 is used. 5) In the control device according to claim 1, the halogen addition means generates halogen gas by photodecomposition of the metal halide, and the halogen concentration control system photodecomposes the metal halide in the halogen addition means. 1. A medium gas control device for an excimer laser, characterized in that the amount of light for the excimer laser is controlled. 6) In the control device according to claim 5, the halogen is fluorine, and the metal halide is AgF.
A medium gas control device for an excimer laser, characterized in that: 7) In the control device according to claim 6, A
A medium gas control device for an excimer laser, characterized in that gF is photodecomposed by ultraviolet light. 8) A medium gas control device for an excimer laser according to claim 1, wherein the halogen addition means is directly inserted into the medium gas circulation system. 9) An excimer laser medium gas control device according to claim 1, wherein the impurity removing means includes a filter for removing solid impurities from the medium gas. 10) In the control device according to claim 1,
1. A medium gas control device for an excimer laser, wherein the impurity removing means includes a low temperature trap for removing gaseous impurities from the medium gas. 11) In the control device according to claim 1,
A medium gas control device for an excimer laser, characterized in that an impurity removal means is inserted at a point of inflow of the medium gas into the excimer laser device in the medium gas circulation system. 12) In the control device according to claim 1,
A medium gas control device for an excimer laser, characterized in that a halogen concentration in the medium gas is estimated from the intensity of laser light output from an excimer laser device. 13) In the control device according to claim 1,
A medium gas control device for an excimer laser, characterized in that the halogen concentration in the medium gas is detected by a gas analyzer. 14) An excimer laser medium gas control device according to claim 13, characterized in that a spectral absorption type is used as the gas analyzer. 15) A control device according to claim 13, characterized in that the gas for the gas analyzer is collected from the medium gas at the outlet point from the excimer laser device in the medium gas circulation system. Media gas control device.