JPH04287992A - Method of removing dust, excimer laser and gas regenerator - Google Patents

Abstract

PURPOSE:To increase a life of laser gas by mounting a magnetic member in a laser gas flow, and attracting fine powderlike dusts to the member to remove the dusts from the gas. CONSTITUTION:A magnetized magnetic member is mounted in laser gas, dusts in the gas are adhered to a surface of the magnetized member by magnetism to be removed. A dust removing unit 3 made of a permanent magnet for removing dusts of a magnetized ferromagnetic material in the gas is mounted in a laser vessel 8 to form a laser gas passage. In an excimer laser, laser gas between discharge electrodes 4 of Ni or Ni-plated metal is preliminarily ionized by an ultraviolet light generated by an arc discharge of a spark gap array 5 of Ni metal, and excited by the discharge of the electrodes 4 to perform a laser oscillation. Thus, a reduction in a laser output is decreased even in an operation for a long time, and a life of the gas is increased.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention deals with impurities in the laser gas of excimer lasers containing halogen gas,
In particular, it relates to the removal of ferromagnetic dust (hereinafter referred to as dust).

0002

2. Description of the Related Art An example of a conventional excimer laser is shown in FIG.

This excimer laser is described in the literature “OPTRONICS” May issue (1988).
6) is described in detail. In this conventional excimer laser, a capacitance transfer type excitation circuit consisting of two sets of capacitors 6 and a thyratron 7 is used in the excitation circuit, a discharge electrode 4 is installed in a laser container 8 that confines the laser gas, and the spark gap array 5 is The laser gas between the discharge electrodes 4 is pre-ionized by the ultraviolet rays generated by the discharge, and the laser gas is excited by the discharge between the discharge electrodes 4.

An example of a conventional gas regenerator used in connection with a laser vessel 8 is shown in FIG. This conventional gas regenerator includes a filter 16 for removing dust from the laser gas, an impurity gas removal section 17 for removing impurity gas, and a filter 16 for removing dust from the laser gas, an impurity gas removal section 17 for removing impurity gas, and a filter for sucking the laser gas in the laser container and returning the regenerated laser gas to the laser container. It is composed of a compressor 18.

In the general excimer laser shown in FIG.
The inside of the laser container 8 is made of a metal material and an insulating material with high halogen resistance in order to prevent deterioration of the laser gas due to corrosion inside, generation of impure gas, and reduction of halogen gas. In particular, Ni or a Ni-plated metal material with excellent halogen resistance is used for the discharge electrode 4 that causes a discharge for laser excitation, and the spark gap array 5 that generates ultraviolet light that pre-ionizes the laser gas is also used. A metal material of Ni is used.

The general gas regenerator shown in FIG. 6 uses a filter 16 and an impure gas removal section 17 to clean the laser gas inside the laser container, which has deteriorated due to impure gas and dust, and returns it to the laser container.

[0007]

[Problems to be Solved by the Invention] In order to oscillate laser light in an excimer laser, the laser gas is pre-ionized with ultraviolet rays generated by the arc discharge of the spark gap array, and the laser gas is excited by the discharge between the discharge electrodes. Therefore, the Ni or Ni-plated metal material of the spark gap array and the discharge electrode is sputtered, and Ni powder or Ni powder chemically reacted with the halogen gas is diffused into the laser gas as dust. This dust is deposited on the surface of the insulating material, deteriorates the insulation properties, and is deposited on the surface of the optical window material, which is a laser resonator, due to laser CVD. As a result, leakage of the high voltage applied between the discharge electrodes is likely to occur, resulting in a decrease in laser gain due to a decrease in the energy injected into the discharge space, and a decrease in laser light extraction efficiency due to deposits on the surface of the optical window. There was a drawback that the output decreased rapidly with the number of shots.

[0008] In a gas regenerator that cleans deteriorated laser gas, an impurity gas removal section removes impurity gas from the laser gas, and a filter removes dust from the laser gas. It cannot be completely removed. For this reason, fine powder dust in the laser gas is deposited on the surface of the optical window material, resulting in a disadvantage that the laser output decreases with the number of operating shots.

The objects of the present invention are to provide a method for removing dust from a laser gas, which reduces the decrease in laser output even during long-time operation and extends the life of the laser gas, and provides an excimer laser with a long laser gas life and a gas regenerator that extends the laser gas life. It is to provide.

0010

A method for removing dust from excimer laser gas according to the present invention is characterized in that dust from laser gas is removed using a magnetic material.

[0011]Furthermore, it is characterized in that dust in the laser gas is removed by installing a magnetic material in the laser container and the gas regenerator, or by composing a part of the constituent material in the laser container with a magnetic material.

0012

[Operation] In the dust removal method according to the present invention, the Ni dust chemically reacted with the Ni sputtered from the Ni discharge electrode or spark gap array used in the conventional excimer laser or the halogen is a ferromagnetic material, and is magnetized. Since the dust adheres to a magnetic material that has been magnetized, it can be easily removed from the laser gas by using a magnetic material that has magnetized the dust. As a result, deposition on the insulating material and the optical window is prevented, a decrease in laser output is suppressed, and the life of the laser gas can be extended.

[0013] In the excimer laser according to the invention, a gas flow path is formed of a magnetized magnetic material so that the laser gas flows in a laminar flow within the laser container for dust removal. Therefore, the probability that the laser gas containing dust passes near the surface of the magnetic material increases, and the dust in the laser gas can be efficiently removed. In addition, since the pressure loss in the gas flow path is reduced, a high gas flow rate can be obtained, and high repetition rate of the laser becomes possible. Further, in the excimer laser according to the present invention in which a magnetized magnetic material is used as a part of the constituent material in the laser container, dust in the laser gas can be removed without increasing the size and complexity of the laser container.

[0014] In the gas regenerator according to the present invention, since a magnetized magnetic body is installed in the gas flow path in the gas regenerator,
It can remove fine dust that cannot be removed even with filters.

[0015]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a structural diagram of an excimer laser which is a second embodiment, and FIG.
4 shows a structural diagram of an excimer laser according to a third embodiment, and FIG. 4 shows a structural diagram of a gas regenerator according to a fourth embodiment.

FIG. 1 is a block diagram for removing dust, which is a ferromagnetic substance, from a laser gas 2. A magnetic substance 1 with magnetism is placed in the laser gas 2, and the dust in the laser gas 2 is magnetically removed. The dust is removed by adhering to the surface of the magnetic material 1 which has a tinge of dust.

Unlike the conventional excimer laser structure whose structure is shown in FIG. 5, FIG. 2 has a dust removal section 3 made of a permanent magnet for removing dust, which is a ferromagnetic substance magnetized in the laser gas. It is installed in a laser container 8, and the dust removal section 3 forms a laser gas flow path. Other than this, the structure is the same as the conventional one. In this excimer laser, the laser gas between the discharge electrodes 4 made of Ni or Ni-plated metal is pre-ionized by ultraviolet light generated by the arc discharge of the spark gap array 5 made of Ni metal, and the laser gas is excited by the discharge between the discharge electrodes 4. to perform laser oscillation. Therefore, due to the discharge between the discharge electrodes 4 and the arc discharge of the spark gap array 5, Ni dust chemically reacted with Ni and halogen gas is diffused from the surface of the discharge electrode 4 and the spark gap array 5 into the laser gas by sputtering of the discharge. However, since this dust is a ferromagnetic substance, it efficiently adheres to the permanent magnet and is removed from the laser gas by the dust removing section 3, which is a permanent magnet installed in the laser container 8 so as to form a laser gas flow path. Furthermore, since the dust removal section 3 forms a flow path for the laser gas, the laser gas flow rate increases, making it possible to repeat the excimer laser at a high rate.

Unlike the structure of the conventional excimer laser whose structure is shown in FIG. A dust removing section 9 is provided. Others are the same as before. Therefore, the dust generated by performing the laser operation as described above with the conventional configuration is attached to the permanent magnet when passing near the heat exchanger, which is the dust removal section 9, and is removed from the laser gas. Can be done. Therefore, the laser container 8 can be prevented from becoming larger and more complicated.

In addition to the configuration of the conventional gas regenerator shown in FIG. 6, FIG. In order to remove dust, a new dust removal section 15 made of a permanent magnet is installed. As a result, fine ferromagnetic dust that cannot be removed by the filter 16 adheres to the permanent magnet and can be removed from the laser gas.

In this way, the ferromagnetic N in the laser gas
Since the Ni dust that has chemically reacted with i and halogen is removed, the accumulation of dust on the surface of the insulating material and the surface of the optical window is suppressed, and the laser output is not decreased and the life of the laser gas is extended.

[0022] In each of the above embodiments, a permanent magnet is used as the magnetic body, but it may also be a magnetic body such as an electromagnet. Further, although an excimer laser is used as the laser, the present invention is not limited to this. Further, in the third embodiment, a part of the heat exchanger is made of a permanent magnet, but at least a part of the other components in the laser container may be made of a magnetized magnetic material. Further, in the fourth embodiment, the dust removal section was installed between the filter and the impure gas removal section, but it is clear that it may be installed at another location.

[0023]

As described above, in the excimer laser using the present invention, the life of the laser gas is extended.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for explaining a dust removal method according to a first embodiment.

FIG. 2 is a structural diagram of an excimer laser according to a second embodiment.

FIG. 3 is a structural diagram of an excimer laser according to a third embodiment.

FIG. 4 is a configuration diagram of a gas regenerator according to a fourth embodiment.

FIG. 5 is a structural diagram of a conventional excimer laser.

FIG. 6 is a configuration diagram of a conventional gas regenerator.

[Explanation of symbols]

1 Magnetic material 2 Laser gas 3,9 Dust removal section 4 Discharge electrode 5 Spark gap array 6 Capacitor 7 Thyratron 8 Laser container 16 Filter 17 Impure gas removal section 18 Compressor

Claims (4)

[Claims] [Claim 1] Ferromagnetic dust (hereinafter referred to as dust) generated in laser gas when a gas laser is operated.
A method for removing dust in a laser gas, characterized in that the dust is removed by adhering to the surface of a magnetized magnetic material (hereinafter referred to as magnetic material). 2. An excitation circuit comprising at least a capacitor, a pair of discharge electrodes for discharging laser excitation, and a switching element; means for pre-ionizing the laser gas between the discharge electrodes; a laser container for sealing the laser gas; In the excimer laser, the excimer laser includes at least a laser gas circulation section that circulates the laser gas in the container, and the pair of discharge electrodes is made of a ferromagnetic metal material with high halogen resistance. An excimer laser characterized by being installed to form a flow path for laser gas. 3. An excitation circuit comprising at least a capacitor, a pair of discharge electrodes for discharging laser excitation, and a switching element; means for pre-ionizing the laser gas between the discharge electrodes; a laser container for sealing the laser gas; an excimer laser comprising at least a laser gas circulation section that circulates laser gas in the container, and in which the pair of discharge electrodes is made of a ferromagnetic metal material with high halogen resistance, wherein at least a part of the constituent material in the laser container is magnetized. An excimer laser characterized by the use of a magnetic material. 4. A filter that includes a Sass inlet and an outlet connected to a laser container filled with laser gas, and removes dust in the laser gas flowing from the gas inlet;
In the gas regenerator, the gas regenerator includes an impurity gas removal unit that removes impurity gas from the laser gas, and a compressor that sucks the laser gas in the laser container and returns the regenerated laser gas into the laser container. A gas regenerator characterized in that a magnetized magnetic material is installed in a laser gas flow path.