JPH029185A - Device for generating fluorine gas for excimer laser - Google Patents

Abstract

PURPOSE:To simplify the structure, reduce size and simplify the operation by a method wherein only fluorine gas is purely generated from a device with fluorine gas generation with metallic fluoride in a heat-melting state subjected to electrolysis. CONSTITUTION:A lid of a vessel is removed, powder stannous fluoride 41 is put into a crucible 23 while sticking it fixed with an electrode rod 26 stood on its support 24, to assemble a generating device. A heater 25 is first applied with power to heat the crucible 23 so as to melt the stannous fluoride 41, maintaining it at 225 deg.C. Then by supplying specified current from a power source 29, the stannous fluoride 41 is subjected to electrolysis, and fluorine gas is generated from the electrode rod 26 serving as an anode. Although tin is gradually deposited or attached to the side of the crucible 23 serving as a cathode at this time, there is no gas generation.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses rare gas and fluorine gas as laser active substances, and supplies fluorine gas to an excimer laser device that lases short wavelength light such as ultraviolet light. The present invention relates to a gas generating device for fluorine gas generation, in which the rate of fluorine gas generation can be adjusted.

[Prior Art] The above-mentioned excimer laser device is a gas laser device suitable for oscillating short wavelength light including about 2,000 ultraviolet light, and as is well known, it uses rare gas atoms such as Ar, Kr, and Xe. The so-called excimer (excited 2f1 body), which is bound to a halogen atom such as fluorine in an excited state, is used as a laser active substance, and the spontaneous emission light emitted when this excimer dissociates becomes a seed, and the light that is stimulated to be emitted afterwards is It is amplified to cause laser oscillation. For this reason, a medium gas prepared by diluting a rare gas such as Kr as the upper excimer and fluorine gas as a halogen with a buffer gas such as Ar is passed through or refluxed through the laser oscillation tube of an excimer laser device. The above-mentioned nitrogen and fluorine as laser active substances are excited into excimers by the discharge.

However, fluorine in this medium gas is extremely reactive, especially at high temperatures, and easily causes a bonding reaction with the constituent materials in the laser oscillation tube and impurities slightly contained in the medium gas, so it is The fluorine concentration in the medium gas decreases quite rapidly, and the resulting change in the composition of the medium gas causes the laser output to gradually decrease. Moreover,
Impurities that react with fluorine have an unfavorable effect on laser oscillation. Therefore, it is desirable to control the medium gas supplied to the excimer laser device so that its fluorine concentration is always constant and does not contain impurities that have reacted with fluorine.

The most reliable means of supplying such a medium gas to an excimer laser device is to constantly supply new medium gas, but this wastes the expensive noble gas contained therein even if the flow rate is reduced to the minimum allowable. In addition, harmful fluorine gas will be emitted from the device to the outside. Therefore,
As a method of supplying medium gas to an excimer laser device, a circulating supply method is usually adopted in which the medium gas is circulated through the laser device, removing impurities that have reacted with fluorine, and replenishing the fluorine consumed by the reaction. . According to this method, the consumption of medium gas is 175~1/
1O, and conversely its lifetime can be extended 5-10 times. At this time, fluorine gas for replenishment is taken out from a dedicated cylinder depending on the amount consumed.

[Problem to be solved by the invention]

However, it is not allowed to store fluorine gas in a cylinder in its pure state because it is highly dangerous, so it is stored in a state diluted with the buffer gas mentioned above. Therefore, in order to replenish the medium gas with fluorine gas, it is necessary to replenish not only the fluorine gas but also the buffer gas, and the medium gas corresponding to the amount of this buffer gas must be released from the circulating supply system. Of course, this emitted medium gas contains noble gas and fluorine gas, so
These expensive laser active materials are wasted and harmful fluorine gas is released. In this way, as long as fluorine gas is supplied to the system in a diluted state, even if a circulating supply system is adopted, it does not necessarily solve all the problems. It is necessary to generate only the amount consumed.

As a method for generating such fluorine, electrolysis of molten K)IF, which has been widely used industrially, is known. However, when this method is applied to a very small-scale fluorine gas generator for excimer laser equipment, the operation is quite cumbersome and the equipment itself is likely to be dangerous.
That is, since the excimer laser device is usually operated under a medium gas of 2 to 3 atmospheres, fluorine must be generated under this atmosphere, and it is necessary to balance the pressure between the negative and negative electrode areas during electrolysis. becomes quite troublesome. Furthermore, during electrolysis, fluorine gas is generated at the anode side and hydrogen gas is generated at the cathode side, so if the two gases do not mix or come into contact, there is a risk of an immediate explosion. be.

Based on the recognition of such problems, the present invention is capable of generating fluorine gas in a pure state by a simple and safe means, and is capable of generating fluorine gas in a pure state in accordance with the amount of fluorine consumed in the medium gas circulation supply system. An object of the present invention is to obtain a fluorine gas generator for an excimer laser whose generation rate can be easily controlled.

[Means for Solving the Problems] According to the present invention, this purpose is to generate fluorine gas by electrolysis of metal fluorides such as stannous fluoride and silver fluoride in a heated and molten state, and to This is achieved by supplying fluorine gas as a laser active substance to the excimer laser device from a fluorine gas generator whose fluorine gas generation rate can be adjusted by controlling the decomposition current.

As the metal fluoride in the above structure, it is practically advantageous to use stannous fluoride or silver fluoride, which have a relatively low melting point. The melting point of each is 210 to 215° for stannous fluoride.
C1 silver fluoride is 435"C. In the case of stannous fluoride, it is heated to about 220 to 230 ° C in an electrolytic crucible to melt it, and with the electrode rod immersed in the melt, By applying electricity with the electrode rod as the anode and the crucible as the cathode,
It is advantageous to electrolyze the stannous fluoride to generate fluorine gas from the scraper side. In the case of silver fluoride, it is heated to a temperature of around 450°C in electrolyzed blood to melt it.
It is advantageous to generate fluorine gas by electrolyzing silver fluoride while causing a discharge between the tip of the electrode rod on the anode side and the electrolytic plate on the cathode side. In either case, the fluorine gas generation rate is adjusted by controlling the current supply or discharge current.

When the fluorine gas generator according to the present invention is used to configure a circulating supply system for a medium gas containing fluorine gas for an excimer laser device, the fluorine gas generator can also be used as a fluorine power source to supply the medium gas at the start of operation of the laser device. It can also be used as a replenishment source for fluorine gas consumed during operation of the device. In the former case, it is preferable to control the generation rate of the fluorine gas generator while measuring the fluorine gas concentration in the medium gas with a spectral absorption type gas analyzer, but in the latter case, it is preferable to control the generation rate of the fluorine gas generator. It is practically advantageous to measure the intensity of the light output and adjust the generation rate of the fluorine gas generator accordingly.

[Effect]

As can be seen from the above structure, fluorine gas is generated by electrolysis of a fluorine-containing compound, which is the same as in the conventional method, but in the present invention, since the object to be electrolyzed is a metal fluoride, it is possible to generate fluorine gas by electrolysis. The difference is that the gaseous product is purely fluorine gas. That is,
The metal fluoride is electrolyzed by electricity when it is heated and molten and has conductivity, and fluorine gas is generated from the anode side, but in the present invention, the electrolyzed metal is only deposited or attached to the cathode side. No gaseous substances are generated.

For this reason, it is no longer necessary to separate gas compartments for the gas generated from the cathode and anode sides, and in the present invention, the pressure vessel of the generator can be made into a single compartment for fluorine gas, so the structure of the equipment is different from that of the conventional one. It is much simpler, there is no need for pressure balancing between the gas compartments, and above all there is no risk of gas mixing or contact.

In addition, the gas generation rate can be adjusted with high precision by simply controlling the current value, since the principle is electrolysis and the amount of gas generated is exactly proportional to the applied current and there is almost no time delay in generation. In addition, fluorine gas can be generated in a desired ratio or amount with good responsiveness.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. 1st
The figure shows a cross section of an embodiment of a fluorine gas generator using stannous fluoride as the metal fluoride, and FIG. 2 shows a cross section of an embodiment using silver fluoride.

As shown in FIG.
It is equipped with two sturdy high-pressure airtight containers, and the gas generator is housed within this container. This container consists of a main body 21 and a lid 22, both of which are made of a metal material with good corrosion resistance to fluorine gas, such as Monel metal, and are hermetically flange-connected to each other as shown. A platform 21a is provided at the bottom of the main body 21 at a position higher than the bottom surface, and the platform 21a and the bottom surface are connected by a cylindrical section 21b formed with a slightly thinner wall to reduce heat conduction.

The electrolytic crucible 23 is a cylindrical body made of a corrosion-resistant metal such as nickel, and is firmly fitted into the upper protrusion of the pedestal 21a. An insulating and heat-resistant electrode support 24 made of fluororesin or the like is inserted into the bottom of the crucible 23. A heater 2 for heating the crucible 23 is provided in a concave portion at the bottom of the main body 21 surrounded by the base portion 21a and the cylindrical portion 21b.
5 is attached. The electrode rod 26 is made of nickel, for example, like the crucible 23, and is attached to the central hole of the crucible 122 through a sheath-like insulating cylinder 27 with a screw-in annular cap 28, supporting its lower end and covering the upper surface of the electrode rod 24. It is fixed in a stable position by inserting it into the hole.

The power supply 29 for electrolysis is a DC power supply that can control the current to a specified value manually and by the current command si, and its positive terminal is connected to the electrode rod 26, and its negative terminal is connected to the container body 21, that is, the crucible 23. Connect as shown.

In this example, the metal fluoride is
Tin 41 is used. To load this into the device, remove the container 122, stand the electrode rod 26 on its support 24, and place the powdered stannous tin 41 into the crucible 23 while thoroughly solidifying it. Assemble the device as shown. Before starting the operation of the apparatus, firstly, the heater 25 is energized to heat the crucible 23, thereby converting the sulfurized tin 4
1 is melted, and its temperature is maintained at a predetermined value of, for example, 225°C by a temperature controller (not shown).

To operate the device, it is sufficient to simply supply a predetermined value of current from the power source 29 to electrolyze the stannous tin fluoride 41, and as described above, fluorine gas is supplied from the electrode rod 26 side, which is the anode for electrolysis. is generated, and tin is only gradually deposited or attached to the crucible 23 side, which is the cathode, and no gas is generated.
In this example, it is assumed that the medium gas G flows through the fluorine gas generator from the inlet/outlet piping, but the inlet/outlet is opened to the piping of the medium gas circulation supply system, and the fluorine gas generated from the apparatus is passed through the fluorine gas generator. It may also be added to the medium gas.

In the fluorine gas generator 1Q shown in FIG. 2, the closed container consists of a main body 31 having a base part 31a and a cylindrical part 31b and a lid 32, as in the above case, but instead of the previous crucible, for example, a nickel-made one is used. An electrolytic dish 33 is attached to the stand 31a,
Silver fluoride 42 is charged as a metal fluoride into the recess on the upper surface. The electrode rod 36 made of nickel or the like is also attached to the hole 1132 via the insulating cylinder 37 with the annular cap 38 as before, but in this embodiment, electrolysis is performed by the discharge current, so the discharge voltage is adjusted and The electrode rod 36 is threaded, as indicated by the arrow tl in the figure, to compensate for some wear on its tip due to discharge during operation.
As shown in D, the annular cap can be loosened to finely adjust its vertical position. During operation of the device, the gap between the tip of the electrode rod 36 and the normalized 1I42 is generally a little less than a few square meters.

The power source 39 is a DC pulse ta with a higher voltage than the previous embodiment, and the electrolytic current is kept constant by controlling the pulse rate of, for example, several sevens. As before, this control operation is performed manually by the electric current a39 or in response to the current command Si. Heater 35 may be similar to the previous embodiment.

However, in this embodiment, after the apparatus starts operating, the silver fluoride is directly heated to a considerable extent by the discharge power.
The heating efficiency of the device will be better than the previous embodiment.

When silver fluoride is used as a fluoride source, the reason why the device is of a discharge type is because the ionization direction of the nickel used in the electrode rod is much thicker than the silver contained in silver fluoride ( This is because if the electrode rod is immersed in molten silver fluoride, nickel will be eluted and its consumption will be significant. Similar to the previous embodiment except that .

FIG. 3 shows an example of application of the excimer laser device of the fluorine gas generator according to the present invention to a medium gas i-ring supply system. In this embodiment, for example, the fluorine gas generator shown in FIG. 1 is used to initially fill the system with medium gas and to replenish consumed fluorine gas in the system. In this embodiment, in addition to fluorine, Kr is used as a rare gas in addition to fluorine as the laser active substance in the medium gas, and Ar is used as a buffer gas.

Inside the excimer laser device 10 shown in the upper part of FIG. 3, there is provided a laser tube 11 whose both ends are closed with transparent windows 12, and a partial reflection mirror 14 and a total reflection mirror 15 on the outside thereof. A laser resonant system is formed by this. The laser tube 11 is discharge excited by a high voltage source 13 and outputs laser light from the partial mirror 14 side.

The circulation supply system shown on the lower side of the laser device 10 is for flowing the medium gas G into the laser tube 11, and the annular path connected by the pipe 60 has a fan 61 for circulating the medium gas. , a fluorine gas generator t20 according to the present invention, which is simply shown by a frame in the figure, and an impurity removal device 50. Among these, the impurity removal device 50 is equipped with a medium gas G
It consists of a filter 51 for removing solid impurities from the medium gas G and a low-temperature trap, and the latter cools the low-temperature container 52 with liquid nitrogen 54 filled between it and the jacket 53 to remove gaseous impurities in the medium gas G by the a-line. It is something.

Furthermore, this circulating supply system includes a discharge valve 62 for discharging air within the system when initially filling it with medium gas G;
A supply system for Kr and ^r in the medium gas G shown at the lower left of the figure is connected. The latter includes cylinders 63 and 64 for storing these rare gases. Those pressure reducing valves 63a and 64a+? JL amount adjustment valves 65 and 66, a shutoff valve 67, etc. are included.

When initially filling the medium gas, first thoroughly exhaust the circulation supply system through the exhaust valve 62, then open the valve of the rare gas supply system and let the gas flow while watching the pressure gauge 72. it adjustment valve 6
5 and 66 to fill the circulation supply system with Ar and Kr to a predetermined pressure and 4 degrees. After the initial filling of the rare gas is completed, the shutoff valve 67 is closed, and the circulating supply system is made into a closed loop that is completely closed from the outside.

Next, while circulating the gas in the system with the fan 61, fluorine is added to the medium gas by manually operating the fluorine gas generator hammer, and the fluorine concentration in the medium gas is set to a predetermined value while watching the pressure gauge 72 as before. raise it to the value. The component ratio in the medium gas at the end of this initial filling is, for example, 96.5% Ar, K
It is assumed that r is 3.0% and fluorine is 0.5%.

In principle, the gas generation rate of the fluorine gas generator (■) during the operation of the excimer laser device (10) should be adjusted so that the amount of fluorine that is gradually consumed in the laser device and the circulation supply system is replenished. However, in this embodiment, the intensity of the laser beam is adjusted to be constant for convenience.The photodetector 71 is used to detect the intensity of the laser beam, and receives a small portion of the laser beam from a small mirror 71a. The detection signal Sd is given to the control circuit 70.The control circuit 70 compares the value of the detection signal Sd with a target value set in advance, and issues a current command 5 to keep the laser light intensity constant.
1 to the fluorine gas generator, and its fluorine gas generation rate! Have J1 section.

It is much easier to detect the intensity of laser light than to detect the fluorine gas concentration in the medium gas, and by adjusting the fluorine gas generation rate based on the laser light intensity as described above, it is possible to detect the fluorine gas in the medium gas. 1 degree can be controlled to be substantially constant. During control based on the laser light intensity or the fluorine gas concentration in the medium gas, the fluorine gas generator according to the present invention generates fluorine gas without time delay at a rate exactly proportional to the value of the given current command Si. The operation of the circulating supply system can be stabilized without over- or under-control.

〔Effect of the invention〕

As explained above, in the fluorine gas generator for excimer laser according to the present invention, fluorine gas is generated by electrolyzing a metal fluoride in a heated molten state.
Since the device only generates pure fluorine gas, the configuration of the device is much simpler and smaller compared to conventional devices that generate gases other than fluorine gas at the same time, making it easier to operate. Moreover, it is possible to completely eliminate the risk of explosion due to mixing or contact between generated gases. In addition, since the device of the present invention can directly adjust the fluorine gas generation rate by controlling the electrolytic current, when it is incorporated into the medium gas circulation supply system of an excimer laser device, it is possible to accurately and time-delay the desired amount of fluorine gas. By generating this without any problem, the control stability of the system can be improved and the performance of the laser device can be improved.

Furthermore, as can be seen from the examples, the present invention can be used both at the time of initial filling of the medium gas in the UIi ring supply system and for replenishing the medium gas with fluorine gas during operation of the laser device. By implementing this, it is possible to eliminate the need to store fluorine gas in the form of a cylinder. Moreover, since the fluorine gas is generated in a pure state as mentioned above, the medium gas is circulated during replenishment, unlike the conventional case of replenishing diluted fluorine gas from a cylinder. There is no need to release it outside the supply system, which eliminates the wasteful consumption of expensive rare gases and the risk of pollution caused by the release of fluorine gas.

As described above, the present invention has the effect of reducing operating costs of an excimer laser device, preventing troubles such as pollution, and simplifying the configuration of the medium gas circulation supply system while improving its operating performance. It is expected that this will contribute to the practical application and development of this type of laser device.

[Brief explanation of the drawing]

The figures all relate to the present invention; FIGS. 1 and 2 are cross-sectional views showing different embodiments of the fluorine gas generator for excimer laser according to the present invention, and FIG. FIG. In the figure, lO: excimer laser device, hammer: fluorine gas generator,
23: Electrolytic crucible, 25; Heater, 26: Electrode rod, 29
; Power source for electrolysis, 30: Fluorine gas generator! , 33: Electrolytic dish, 35: Heater, 36: Electrode rod, 39: Power source for electrolysis,
41: Stannous fluoride as a metal fluoride, 42: Silver fluoride as a metal fluoride, 50: Impurity removal device! ,7
0: Control n circuit, G: Media waste, L elm-"l'Sd
; Laser light intensity detection signal, fluorine gas Figure 3

Claims (1)

[Claims] 1) A device for generating fluorine gas as a laser active material to be supplied to an excimer laser device at an adjustable rate, the device generating fluorine gas by electrolysis of a metal fluoride in a heated molten state. A fluorine gas generator for an excimer laser, characterized in that the rate of fluorine gas generation can be adjusted by controlling the electrolysis current. 2) A fluorine gas generating device for an excimer laser according to claim 1, wherein the metal fluoride is stannous fluoride. 3) A fluorine gas generating device for an excimer laser according to claim 1, wherein silver fluoride is used as the metal fluoride.