JPH03200388A - Excimer laser apparatus - Google Patents

Abstract

PURPOSE:To increase the life of a shaft seal and to improve maintenance and economy by providing a gas reservoir for so forming a curtain of laser gas as to block a gap by spraying clean laser gas supplied from a supply unit along the outer periphery of a shaft. CONSTITUTION:A motor is driven to rotate a shaft 21 to rotate a fan, thereby circulating laser gas. Magnetic fluid 22 is collected between the inside of protrusion stripes 15 of pole pieces 13, 14 and the shaft 21 in a magnetic field of a magnet 16 to seal it therewith. On the other hand, clean laser gas 27 supplied to a gas reservoir 24 from the unit through a supply tube 26 is sprayed from a gap 27 provided between the shaft 21 and the reservoir 24 to form a curtain along the outer periphery of the shaft 21 with the sprayed gas 27, thereby preventing powder dusts from invading into a shaft seal 17 from a gap 23 between the shaft 21 and a housing 2. Thus, the life of the seal is increased, and maintenance, economy are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an excimer laser device using rare gas halide discharge excitation.

BACKGROUND OF THE INVENTION Recently, excimer lasers using rare gas halide discharge excitation have been attracting attention in the semiconductor industry and the photochemical field as high-efficiency optical output lasers in the Shigai line region. Among them, Xe0I (308nm
), KrF (248 nm) excimer laser devices have received the most attention.

Excimer lasers are filled with rare gas and halogen gas, and emit the necessary light by discharge excitation. Since the enclosed laser gas contains about 0.2 to 0.3% by weight of halogen gas such as F2 and Hot, it reacts with the main electrode, pre-ionization electrode, and other structures of the laser oscillator. It is chemically decomposed and impurity gas is generated. This impurity gas and halogen gas are adsorbed to the surface of the pressure vessel and are reduced, resulting in a decrease in laser output. In addition, depending on the degree of mismatch in the electrical circuit and the amount of impurity gas generated,
Arcing occurs between the discharge electrodes, causing a large current discharge.

Therefore, solid impurities (dust) are generated due to sputtering from electrodes and the like.

Therefore, in order to obtain a constant output for a long time without generating impurity gases, a method has been adopted in which clean laser gas is injected at a rate of several tens of cc/min.

Generally, in such excimer lasers, a fan is rotated inside a container containing laser gas in order to circulate the laser gas, but the motor that rotates the fan is corroded by the halogen gas contained in the laser gas. It is placed outside the pressure vessel. Therefore, the shaft bearing that transmits the rotation of the motor to the fan must not destroy the airtightness of the pressure vessel, and shaft seals or magnetic couplings using magnetic fluid are used to satisfy this condition. It is being

Hereinafter, the conventional shaft seal using magnetic fluid will be described with reference to the cross-sectional view shown in FIG. 2.

As shown in FIG. 2, the housing 1 has end plates 3 and 4 connected to the inner and outer ends of the body 2, respectively, and the outer end plate 4 has a flange portion 5 protruding from each end plate. A hole 6.7 is formed in the center of 3.4 on the same axis. Inside the housing 1 are bearings 8.9 along the inner surface of each end plate 3.4.
The bearing 8.9 has an outer race 10, an inner race 11, and balls 12 held in a retainer (not shown) between the outer race 101 and the inner race 11, and each outer race 10 is connected to the body. It is fixed to the inner surface of part 2.

Ring-shaped pole piece 1 inside each bearing 8.9
3.14 is fixed to the inner surface of the body 2, and each pole piece 1
3.14 has a plurality of protrusions 16 formed on the inner circumference, and the protrusions 1
The inner diameter of the bearing 8.6 is set to be slightly larger than the inner diameter of the inner race 11 of the bearing 8.9. pole piece 1
A ring-shaped magnet 16 is inserted between 3 and 14.

The shaft seal 17 configured in this way has its housing 1
The body 2 is a hole 2o formed in the wall 19 of the pressure vessel 18.
The shaft 21 is inserted into the hole 7. of the housing 1, and the flange portion 6 is fixed by coming into contact with the outer surface of the wall 19, and the shaft 21 is inserted into the shaft seal 17. Bearing 9, pole piece 14, magnet 16
, the pole piece 13, the inner sides of the bearing 8, and the hole 6 of the housing 1, and are fixed to the inner race 11 of each bearing 8.9. The outer end of the shaft 21 is linked to a motor (not shown), and the inner end is linked to a fan (not shown) for circulating laser gas.

The operation of the above configuration will be described below.

The shaft 21 is rotated by driving the motor, the fan is rotated accordingly, and the laser gas can be circulated.

Then, due to the magnetic field created by the magnet 16, the pole piece 13.
The magnetic fluid 22 is collected between the shaft 21 and the inside of the 14 protrusions 16, and the magnetic fluid 22 can provide a seal. At this time, each stage of the ridges 16 of the pole pieces 13, 14 can have a withstand pressure of 0.2 to 0.3 atmospheres. Generally, an excimer laser device is operated at a laser gas pressure of about 1.6 to 2.0 atmospheres, so a shaft seal 17 is used in which the protrusions 16 of the pole pieces 13 and 14 are provided in about 10 stages.

Problems to be Solved by the Invention However, in the conventional configuration as described above, the dust generated due to the discharge as described above is caused to flow from the gap 23 between the inner circumferential wall of the hole 6 of the housing 2 of the shaft seal 17 and the shaft 21. This intrudes and significantly shortens the life of the shaft seal 17.

The present invention provides an excimer laser device that can reduce the intrusion of dust into a shaft seal using magnetic fluid, extend the life of the shaft seal, and improve maintainability and economic efficiency. The purpose is to

Means for Solving the Problems The technical means of the present invention for solving the above problems is to use a magnetic fluid to seal a shaft that is attached to the wall of a pressure vessel and has both sides located outside and inside the pressure vessel. a shaft seal provided inside the pressure vessel so as to cover the gap between the shaft and the housing of the shaft seal on the outer periphery of the shaft, and connected to a clean laser gas supply section; A gas reservoir is provided for blowing out the supplied clean laser gas along the outer periphery of the shaft to form a curtain of laser gas so as to close the gap.

Therefore, according to the present invention, the clean laser gas supplied from the supply section to the gas reservoir is blown out along the outer periphery of the shaft to close the gap between the housing of the shaft seal using magnetic fluid and the shaft. Since a laser gas curtain is formed in the gap, dust can be prevented from entering the gap.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway side view showing a shaft seal portion used in an excimer laser device according to an embodiment of the present invention.

In this embodiment, the structure of the shaft seal 17 is the same as that of the conventional example shown in FIG. 2, so the same reference numerals are given and the explanation thereof will be omitted, and the different structure will be explained. As shown in FIG. 1, inside the pressure vessel 18, a gas reservoir 2 is provided on the outer surface of the end plate 3 inside the housing 2 of the shaft seal 17.
The gas reservoir 24 is formed on the outer periphery of the shaft 21 to cover the gap 23 between the shaft 21 and the inner wall of the hole 6 of the housing 20 of the shaft seal 17. A gap 26 is formed between.

One end of a supply pipe 26 is connected to the outer peripheral wall of the gas reservoir 24, and the other end of the supply pipe 26 is connected to a clean laser gas supply part (not shown) outside the pressure vessel 18. Then, the clean laser gas 2□7 supplied from the supply section to the gas reservoir 24 through the supply pipe 26 is blown out from the gap 26 along the outer circumference of the shaft 21, and the gap 23 between the shaft seal 17 and the shaft 21 is The structure is such that a curtain of laser gas can be formed to block the area.

The operation of the above configuration will be described below.

The shaft 21 is rotated by driving the motor, the fan is rotated accordingly, and the laser gas can be circulated.

Then, due to the magnetic field created by the magnet 16, the pole piece 13.
The magnetic fluid 22 is collected between the shaft 21 and the inside of the 14 protrusions 16, and the magnetic fluid 22 can provide a seal. On the other hand, the clean laser gas 27 supplied from the supply section to the gas reservoir 24 through the supply pipe 26 as described above is temporarily retained in the gas reservoir 24, and the clean laser gas 27 is removed from the gap provided between the shaft 21 and the gas reservoir 24. 26 is also blown out. This blown laser gas 27 forms a curtain along the outer periphery of the shaft 21 to prevent dust from entering the shaft seal 17 through the gap 23 between the shaft 21 and the housing 2.

Effects of the Invention As described above, according to the present invention, the clean laser gas supplied from the supply section to the gas reservoir is blown out along the outer circumference of the shaft, and the housing and shaft of the shaft seal using magnetic fluid are connected. Since a laser gas curtain is formed to close the gap, it is possible to prevent dust from entering the gap. Therefore, the life of the shaft seal using magnetic fluid can be extended, and maintainability and economical efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view showing a shaft seal portion used in an excimer laser device according to an embodiment of the present invention, and FIG. 2 is a sectional view of a shaft seal portion used in a conventional excimer laser device. 1...Housing, 8.9...Bearing, 13.
14... Pole piece, 16... Magnet, 17...
Shaft seal, 18... Pressure vessel, 21... Shaft, 22.
...Magnetic fluid, 23...Gap, 24...Gas reservoir,
26... Gap, 27... Laser gas.

Claims (1)

[Claims] a shaft seal that is attached to the wall of the pressure vessel and seals a shaft with both sides located outside and inside the pressure vessel using a magnetic fluid; and a shaft seal that is attached to the outer circumference of the shaft inside the pressure vessel, is provided to cover the gap between the housing and the housing, and is connected to a clean laser gas supply section, and the clean laser gas supplied from the supply section is blown out along the outer periphery of the shaft to fill the gap. An excimer laser device equipped with a gas reservoir to form a curtain of laser gas.