JPH06275902A - Excimer laser device - Google Patents

Abstract

PURPOSE:To provide a laser gas purifying device which does not generate reacting gas by providing an impurity removing device which permits metal fluoride compound or hydrogen fluoride metal compound or the mixed material of such compounds to make contact with the laser gas at the time of removing impurities in the laser gas by adsorption. CONSTITUTION:Impurity removing devices 62a and 62b which permit metal fluoride compound or hydrogen fluoride metal compound or the mixed material of such compounds to make contact with laser gas is provided so as to remove impurities in the laser gas by adsorption. As for the fluoride metal compound or the hydrogen fluoride metal compound, alkali metal compound or iron compound is used. As for the metal fluoride compound, one of the following is used: LiF, NaF, KF, RbF, CsF, AgF, CoF2, NiF2 and FeF2. Thus, HF, which is the major cause for reducing laser power, is removed from the laser gas and the life of the laser gas is remarkably lengthened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excimer laser device, and more particularly to an excimer laser used as a light source for an exposure device for microfabrication of polymer, ceramic or metal.

[0002]

2. Description of the Related Art Conventionally, ArF, KrF, and XeF excimer lasers are examples of fluorine excimer lasers. F2 gas and rare gas (Ar, Kr, Xe), which have extremely high reactivity, are used as the laser gas, and He and Ne gases are used as the buffer gas. Impurities generated while the laser is operating or stopped are CF4, SiF4, HF, NF
3, fluorine compounds such as C2F6 and O2, and the following methods have been conventionally proposed for the purpose of removing these impurities or suppressing their generation. (1) A low temperature trap method in which a laser gas is cooled and a substance having a relatively high boiling point is condensed by utilizing a vapor pressure difference between the laser gas and impurities. (2) A metal calcium method in which a substance capable of reacting with metal calcium is brought into contact with metal calcium to form a calcium compound. (3) An adsorption method of adsorbing a substance to be adsorbed with activated carbon or a getter material (Ti-Zr alloy). (4) A method in which a laser gas is brought into contact with a solid alkali metal and / or alkaline earth metal compound and then brought into contact with zeolite (Japanese Patent Publication No. 4-46607). In the method of Japanese Patent Publication No. 4-46607, as shown in FIG. 8, a laser gas is first inserted into a solid alkali filling tube 93, and the active substance B, for example, F2, HF which is the main component, is reacted by the reaction with the solid alkali compound. SiF4 and the like are removed, and are further inserted into the zeolite filling tube 94 to remove residual impurities C such as C2F6, CF4 and NF3 by adsorption on the zeolite. Then, a rare gas such as He, Ar, or Kr is circulated to the laser device 91. On the other hand, the removed F2 gas is replenished. (5) On the other hand, as a method for suppressing the generation of impurities, by using a metal (for example, Ni, Al) and a ceramic (for example, Al2O3) that are corrosion resistant to fluorine as a material used in the laser chamber, The number of sources was reduced, and the amount and type of impurities were reduced.

[0003]

However, in the low temperature trap method of the above (1), the F2 gas is not trapped, but liquid nitrogen is required to keep the laser gas at a low temperature. Therefore, the liquid nitrogen supply system is used. Required, and handling was also very troublesome. (2),
In the methods (3) and (4), the F2 gas is adsorbed or reacted with the impurities to be removed, so that it is necessary to supply the trapped F2 gas separately to supplement the trapped F2 gas. Was becoming. Further, in the method (4), soda lime, CaO,
Since Ca (OH) 2 and the like are used, HF and F2 are absorbed, but at that time, H2O and O2 generated are removed by zeolite.

[Chemical 1] CaO + 2HF → CaF2 + H2O

## STR00002 ## In the method of 2CaO + 2F2 → 2CaF2 + O2 (5), the substance having a large amount of impurities is HF, and this HF was the main factor that determines the gas life of the laser. As described above, there has been a problem that a refining device for a laser gas has not been proposed so far, which removes the impurity gas without trapping the F2 gas by a method other than the low temperature trap method and does not generate a reaction gas.

The present invention focuses on the above-mentioned conventional problems, and relates to an excimer laser device, and in particular, it does not react with F2 gas but reacts with HF which is an impurity gas to generate a hydrogen fluoride compound and immobilize it. An object of the present invention is to provide a laser gas purifying apparatus that removes HF by bringing a laser gas into contact with a substance, that is, a metal fluoride compound, a hydrogen fluoride metal compound or a mixture thereof, and does not generate a reaction gas.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, at least a metal fluoride compound, a hydrogen fluoride metal compound, or the above-mentioned compound is used when adsorbing and removing impurities in a laser gas. It has an impurity removing device for bringing the laser gas into contact with the mixture.

In the second invention mainly based on the first invention, the metal fluoride compound or the hydrogen fluoride metal compound is an alkali metal compound or an iron group compound.

In the third invention mainly based on the first invention, the metal fluoride compound is LiF, NaF, KF, RbF, CsF, AgF, CoF2, NiF2 or FeF2.

In the fourth invention mainly based on the first invention, as the hydrogen fluoride metal compound, KF.HF or KF.2H is used.
F or CsF · HF or CsF · 2HF.

In the fifth aspect of the invention, which is mainly the first aspect of the invention, the impurity removing device is disposed upstream or downstream of the dust removing device of the dust filter system that removes dust in the laser gas to prevent window contamination.

In a sixth aspect of the invention, which is mainly the first aspect of the invention, an impurity removing device is provided in the dust filter system, forming a gas circulation route in parallel therewith.

In the seventh invention, which is mainly based on the first invention, impurities are removed by utilizing a differential pressure generated by a fan that circulates gas between electrodes during laser oscillation in gas circulation of the dust filter / impurity removing system. To do.

In the eighth aspect of the invention, which is mainly based on the first aspect, a pump is used for gas circulation in the dust filter / impurity removing system to remove a part of the laser gas to remove impurities.

[0013]

According to the above construction, examples of the metal fluoride compound, the hydrogen fluoride metal compound or the mixture thereof are, for example, LiF, NaF, KF, CsF, RbF and Ag.
There are F, CoF, NiF, NiF2, FeF2 and the like. The reaction formulas of these compounds for HF are shown below.

Embedded image LiF: LiF + HF → LiF.HF

[Chemical formula 4] NaF: NaF + HF → NaF / HF

[Formula 5] KF: KF + HF → KF ・ HF KF ・ HF + HF → KF ・ 2HF KF ・ 2HF + HF → KF ・ 3HF KF + 2HF → KF ・ 2HF KF + 3HF → KF ・ 3HF

[Image Omitted] CsF: CsF + HF → CsF.HF CsF + 2HF → CsF ・ 2HF CsF + 3HF → CsF ・ 3HF, etc.

Embedded image RbF: RbF + HF → RbF · HF

Embedded image AgF: AgF + 3HF → AgF · 3HF

[Chemical formula 9] CoF: CoF2 + 5HF → CoF2.5HF

Embedded image NiF: NiF2 + 5HF → NiF2 · 5HF As described above, since these compounds are fluorides, F2
Does not react with, but only HF reacts and is adsorbed. Moreover, the reaction product is a solid and does not generate an impurity gas (O2, H2O, etc.).

FIG. 1 shows the principle of the present invention. In the fluorine-based excimer laser 1, a laser chamber 4 having windows 2 and 3 at the front and back is filled with fluorine gas, a rare gas, and a buffer gas. For example, light emitted by discharge excitation emits light from a front mirror 5 and a rear mirror 6. Laser oscillation (L) is generated by the empty resonator. A part of the laser gas is sent to the metal fluoride compound filling pipe 7 installed in the laser gas circulation circuit (M) and absorbs HF which is an impurity gas generated in the laser gas. Metal fluoride compound filling tube 7
The laser gas from which the HF has been removed is returned to the laser chamber 4 again. Thus, by bringing the laser gas into contact with the metal fluoride compound, the hydrogen fluoride metal compound, or a mixture thereof, only HF, which is the main cause of the laser output reduction, can be efficiently trapped at room temperature, and no reaction product gas is generated. Therefore, the gas life of the laser can be dramatically extended.

[0015]

Embodiments of the excimer laser device according to the present invention will be described below in detail with reference to the drawings. Figure 1
The same parts as those in FIG. Figure 2
Shows a schematic diagram of one embodiment in which the circulating laser gas is externally circulated by the pump 11 of the excimer laser device 1 of the present invention. In FIG. 2, a part of the laser gas is sucked by the pump 11 of the external circulation circuit (N) and sent to the filter 12. After removing dust in the laser gas by a filter, the dust is sent to the metal fluoride compound filling tube 7,
HF which is an impurity gas is removed during permeation through the filling pipe 7. Then, it is returned to the laser chamber again. Here, the reason why the filter 12 is allowed to pass through before passing through the metal fluoride compound-filled tube is that dust does not adhere to the metal fluoride compound and reduce the HF adsorption capacity. However,
The present invention is not limited to this embodiment, and the filter 13 may be arranged after passing through the metal fluoride compound filling tube.

FIG. 3 shows an example in which the HF and dust-removed gas that has passed through the metal fluoride compound filling tube is introduced into the laser window. Part of the laser gas is sucked by the pump 21 in the external circulation circuit (P) and sent to the filter 22. After dust in the laser gas is removed by the filter 22, the dust is sent to the metal fluoride compound filling pipe 7, and HF which is an impurity gas is removed while passing through the filling pipe 7. The laser gas from which HF and dust have been removed by the filling tube 7 is branched into two, a front side circuit (Pa) and a rear side circuit (Pb), and the laser chamber 4 near the front side window 2 and the rear side window 3 is divided. Returned inside. By doing this, dust and H
It is possible to prevent the adsorption of F. Therefore, the window life can be dramatically extended.

FIG. 4 shows an example in which an apparatus for regenerating a metal fluoride compound is installed. In the external circulation circuit (Q) in FIG. 4, valves 31 and 32 are installed before and after the metal fluoride compound filling pipe 7, and a heater 33 and / or a cooler 34 is provided in the metal fluoride compound filling pipe 7. Install. Further, the metal fluoride compound filling pipe 7 is provided with a circuit for sending it to an exhaust device (not shown) through the vacuum pump 35 and exhausting it. The valves 31, 32, the heater 33 or / and the cooler 34, and the vacuum pump 35 receive signals from the CPU 36 via the driver 37, and are respectively driven. A timer 38 is attached to the CPU 36 to measure the operating time of the laser device.

Next, the operation will be described. The following reverse reaction proceeds by heating with a heater. For example, when the metal fluoride compound is KF,

Embedded image KF · HF → KF (solid) + HF (gas) T = 223 ° C. Therefore, by heating to 223 ° C., HF gas can be discharged to regenerate KF. FIG. 5 shows a flowchart for regenerating the metal fluoride compound. First, step 101
At, it is determined whether or not the metal fluoride compound is regenerated. When reproducing, the valves 31 and 32 are closed by a signal from the CPU 36 (step 10).
2). Then, in step 103, the heater 33 and the vacuum pump 35 are operated. Next, at step 104, it is judged whether or not the operating time K during which the HF is sufficiently discarded has been exceeded.
If the operating time T exceeds K in step 104, the heater 3
3 and the vacuum pump 35 are stopped (step 10).
5). After that, the valves 31 and 32 are opened and the HF
Return to the trap state (step 106).

Further, the judgment in this case may be made by a human, or may be made by the CPU 36 from the operating time. Further, the determination may be made based on the signal from the gas sensor 39. As this method, a gas sensor 39 for detecting an impurity gas such as HF is provided in the laser chamber 4, and the detected signal is transmitted to the CPU 36 of the controller. The CPU 36 makes a determination based on the signal from the gas sensor 39, passes through the driver 37, the valves 31, 32,
Heater 33 or / and cooler 34, vacuum pump 3
5 is sent to control each drive.

In FIG. 4, the heater 33 or the cooler 3
The reason for using No. 4 is that depending on the kind of the metal fluoride compound, for example, in NiF2, CoF2, and AgF, HF is better when cooled.
Because of its high absorption capacity, the cooler (ice, water, heat pump, thermoelectric element, etc.) is activated in the HF trap state, and is heated by the heater (heat pump, thermoelectric element, etc.) in the regenerated state, as shown in FIG. You may reproduce according to a simple flowchart. Furthermore, the metal fluoride compound has a stable crystal state, and when crystal water is contained, it reacts with F2 to produce O2.
It is not preferable because it is discharged.

[Image Omitted] 2F2 + 2H2O → 4HF + O2 (gas) Therefore, it is necessary to heat the metal fluoride compound in order to discharge the water of crystallization.

For example, in the case of KF, the following reaction proceeds.

Embedded image KF · 4H 2 O → KF + 4H 2 O (gas) T = 40 ° C. The water of crystallization can be removed by heating to 40 ° C. The system for removing the water of crystallization can remove the water of crystallization by the same system as that for regenerating HF as shown in FIG. 4 and by the procedure of the flowchart similar to FIG.

FIG. 6 shows an example in which the impurity removing device is installed in the laser tube. In FIG. 6, the impurity removing device is arranged after the dust filter is filtered at the position where the gas utilizing the differential pressure generated by the cross flow fan in the laser tube circulates. In FIG. 6, 41 is a laser chamber for enclosing a predetermined laser gas, 42 is a cross flow fan, 43 and 44 are main electrodes, 45 is a fan drive motor, 46a is a front window, 46b is a rear window, and 47 is a window. The holder 48 is a labyrinth. A dust filter case 49 is attached to the laser chamber 41, and the laser chamber 41 and the dust filter case 49 communicate with each other through a dust filter inlet 50 provided substantially at the center in the optical axis direction. In addition, the gas introduction passages 51 provided in the wall surfaces of both ends of the laser chamber 41.
And the dust filter outlets 52 provided at both ends of the dust filter case 49. The dust filter outlet 52 communicates with the sub chamber 53 accommodating the labyrinth 48 and the front window 46a, or the sub chamber 53 and the rear window 46b, and then returns to the laser chamber 41 via the labyrinth 48. In the dust filter case 49, an impurity removing member 55a for the front window and an impurity removing member 55b for the rear window are provided.
Is provided. The impurity removing members 55a and 55b are
It is composed of a filter 56, a metal fluoride compound 57, and a metal mesh filter 58. The metal fluoride compound 57 may be filled and confined in the space partitioned by the metal mesh filter 58 so as not to scatter. The mesh filter 58 is made of a metal such as stainless steel, nickel, monel, or copper that is not affected by fluorine. A front mirror 59 or a rear mirror 60 is provided outside the front window 46a or the rear window 46b.

Next, the operation will be described. For example, Kr
In the case of the F excimer laser, the laser gas is Kr gas, the halogen gas is fluorine gas, and the buffer gas is Ne or He or a mixed gas thereof. The laser gas is circulated in the laser chamber 41 by the cross flow fan 42, and a new gas constantly flows between the main electrodes 43 and 44 so that stable pulse discharge is performed at the main electrodes 43 and 44. Then, the light excited by this discharge is amplified by the resonators of the front mirror 59 and the rear mirror 60 and oscillates as a laser. On the other hand, a part of the laser gas that is internally circulated is part of the dust filter inlet 5.
From 0, it enters the dust filter case 49 and passes through the impurity removing member 55a for the front window and the impurity removing member 55b for the rear window. In the impurity removing members 55a and 55b, dust is removed by the filter 56 and the metal mesh filter 58, and HF is removed from the laser gas by the metal fluoride compound 57 to obtain a clean laser gas.

This clean laser gas passes through a dust filter outlet 52 and a gas introduction path 51 in the wall surface of the laser chamber.
Pass through the sub chamber 53 and the front window 46a for accommodating the labyrinth 48, or enter the sub chamber 53 and the rear window 46b. The sub-chamber 53 is provided on the laser optical path and forms a buffer region for stabilizing the flow of the inflowing gas. Here, the laser gas that has recovered to the static state flows through the labyrinth 48 toward the main electrodes 43 and 44 in the laser chamber 41 without moving the clean laser gas that stays near the inner surfaces of the windows 46a and 46b. Therefore, the laser gas from which dust and HF have been removed enters the main electrodes 43 and 44, and pulse discharge is performed without deteriorating the performance.

FIG. 7 shows another embodiment in which the impurity removing device is installed in the laser tube. In FIG. 7, a gas circulation circuit is provided in parallel with a window purge mechanism (not shown), and the laser gas is introduced into the impurity removing device by utilizing the differential pressure generated by the cross flow fan. The same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. An impurity removing member 62 a and an impurity removing member 62 b are arranged in the impurity removing case 65. Impurity removing members 62a, 6
2b is composed of a metal fluoride compound 63 and a mesh filter 64 made of metal. The metal fluoride compound 63 is filled and confined in the space partitioned by the metal mesh filter 64 so as not to scatter.

Next, the operation will be described. A part of the laser gas circulated internally enters the impurity removing device case 65 through the impurity removing device inlet 66, and the impurity removing member 62
a and the impurity removing member 62b. In the impurity removing members 62a and 62b, while being held by the metal mesh filter 64, HF is removed from the laser gas by the metal fluoride compound 63 to become clean laser gas, and the gas outlets 61a and 61 at both ends of the laser chamber 41 are formed.
It returns to the inside of the laser chamber 41 through b. Therefore, dust, H
The laser gas from which F has been removed enters the main electrodes 43 and 44,
Pulse discharge is performed without degrading the performance.

1 to 5, the metal fluoride compound filling tube is described, but the invention is not limited to this.
The filling tube may be filled with at least a metal fluoride compound, a hydrogen fluoride metal compound, or a mixture thereof. Further, in FIGS. 6 and 7, a metal fluoride compound is used, but a hydrogen fluoride metal compound or a mixture thereof may be used similarly to the above, and the metal fluoride compound may be covered with a metal mesh filter to be integrated. The cassette type may be exchangeable. Further, although the above passage is also provided in the center, the entrance may be provided on one side.

[0028]

As described above, according to the present invention, the gas life of the laser can be remarkably extended by removing HF, which is the main cause of lowering the laser output, from the laser gas. . 2 Since the HF concentration in the gas near the window decreases, it is less likely to be adsorbed by the window and the window life is extended. 3 Since only HF which is an impurity is adsorbed and fluorine which is a halogen donor is not adsorbed in the process of gas purification, the impurities can be removed without affecting the laser gas composition. That is an excellent effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the principle of the present invention.

FIG. 2 is a schematic diagram of an embodiment in which the circulating laser gas of the present invention is externally circulated.

FIG. 3 shows H permeated through a metal fluoride compound-filled tube of the present invention.
The schematic diagram of the Example which introduce | transduced the gas which removed F and dust into the window of the laser.

FIG. 4 is a schematic view of an example in which an apparatus for regenerating a metal fluoride compound of the present invention is installed.

FIG. 5 is a flow chart when regenerating the metal fluoride compound of the present invention.

FIG. 6 is a schematic view of an example in which the impurity removing device of the present invention is installed in a laser tube.

FIG. 7 is a schematic view of another embodiment in which the impurity removing device of the present invention is installed in a laser tube.

FIG. 8 is a schematic diagram of an example of a conventional impurity removing apparatus.

[Explanation of symbols]

 1 Excimer Laser Device 2, 3 Window 4, 41 Laser Chamber 5 Front Mirror 6 Rear Mirror 7 Fluoride Metal Compound Filling Tube 11, 21 Pump 12, 13, 22 Filter 31, 32 Valve 33 Heater 34 Cooler 35 Vacuum Pump 36 CPU 37 Driver 38 Timer 42 Cross-flow fan 43, 44 Main electrode 45 Fan drive motor 46a Front window 46b Rear window 47 Window holder 48 Labyrinth 49 Dust filter case 55a, 55b Impurity removing member 56 Filter 57 Fluorinated metal compound 58 Metal Mesh filter 61a, 61b Gas outlet path 62a, 62b Impurity removing device 63 Metal fluoride compound 64 Mesh filter 65 Impurity removing case 66 Impurity removing inlet

Claims (8)

[Claims] 1. A fluorine-based excimer laser, comprising an impurity removing device for bringing the laser gas into contact with at least a metal fluoride compound, a hydrogen fluoride metal compound, or a mixture of the compounds when adsorbing and removing impurities in the laser gas. apparatus. 2. The fluorine excimer laser device according to claim 1, wherein the metal fluoride compound or the hydrogen fluoride metal compound is an alkali metal compound or an iron group compound. 3. LiF, NaF, KF, RbF, CsF, or Ag as the metal fluoride compound.
The excimer laser device according to claim 1, which is F, CoF 2, NiF 2, or FeF 2. 4. KF.H as the hydrogen fluoride metal compound
F or KF ・ 2HF or CsF ・ HF or CsF
The excimer laser device according to claim 1, which is 2HF. 5. The excimer laser device according to claim 1, wherein the impurity removing device is arranged upstream or downstream of the dust removing device of the dust filter system for removing dust in the laser gas to prevent the window from being contaminated. 6. The excimer laser device according to claim 1, wherein a gas circulation path is formed in parallel with the dust removing system and the impurity removing device is arranged therein. 7. The excimer laser device according to claim 1, wherein impurities are removed by utilizing a differential pressure generated by a fan that circulates a gas between the electrodes during laser oscillation in the gas circulation of the dust filter / impurity removing system. 8. The excimer laser device according to claim 1, wherein a part of the laser gas is taken out to remove impurities by using a pump for gas circulation in the dust filter / impurity removing system.