JPH03254165A - Gas laser apparatus - Google Patents

Abstract

PURPOSE:To protect the inner face of a window member against damage, when the window member is left as it is for a long time after being removed from a laser container, by providing a shutter for tightly closing the inner face side of the window member in the inner space of a holder when it is rotated to a state opposing to the inner face of the window member in the holder. CONSTITUTION:The gas laser apparatus comprises a holder 4 mounted detachably while being jointed airtightly, at one end side, at a position opposing to the opening of a hollow laser container 1 for passing laser beam generated in the laser container 1, a window member 3 arranged air-tightly and detachably at the other end side of the holder 4, and a shutter 18 arranged rotatably in the holder 4 so that the inner face side of the window member 3 in the inner space of the holder 4 is closed tightly when the shutter is rotated to a state opposing to the inner face of the window member 3. After the shutter 18 is rotated to a state opposing to the window member 3, the window member 3 is dismounted from the laser container 1 together with the holder 4. Consequently, even if the window member 4 is left as it is for a long time with dust being adhered thereto, the inner face of the window member is protected against damage due to contact of the inner face with the atmospheric air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a gas laser device that excites a gas laser medium by a glow discharge generated at a main electrode to generate laser light.

(Prior art) For example, an excimer laser, which is a gas laser device, uses a rare gas such as Kr (krypton) or Xe (xenon) as a gas laser medium, a halogen gas such as F2 (fluorine) or C20 (hydrogen chloride), and He ( Helium) and Ne(
A mixed gas containing a buffer gas such as neon) is used.

A gas laser medium made of such a mixed gas is housed in a laser container. A main electrode is disposed within the laser container, and the gas laser medium is excited by the glow discharge generated at the main electrode to generate laser light. Furthermore, openings are formed on both axial end faces of the laser container, and each opening is hermetically closed by a window member made of an optical material that transmits laser light. A high-reflection mirror is disposed to face one of the window members, and an output mirror that forms an optical resonator with the high-reflection mirror is disposed on the other window member. Laser light generated by exciting the gas laser medium is amplified by an optical resonator and oscillated from the output mirror.

When a gas laser device with such a configuration is operated for a long time,
It is inevitable that dust such as discharge products will adhere to the inner surface of the window member. If dust adheres to the window member, the transmittance of laser light will decrease, resulting in a decrease in output. Therefore, in the gas laser device, the window member is removed from the laser container and cleaned every time the gas laser device is operated for a predetermined period of time.

By the way, when the gas laser device is, for example, a KrF excimer laser, fluoride is mixed in the dust that adheres to the inner surface of the window member. Therefore, when the window member is removed from the laser container for cleaning and left in the atmosphere for several hours, the fluoride reacts with moisture in the atmosphere to generate hydrofluoric acid. This hydrofluoric acid damages the antireflection coating coated on the inner surface of the window member. Therefore, after removing the window member, it is sufficient to clean it immediately, but if the gas laser device is installed in a place where dust cannot be generated, such as in a clean room, cleaning the window member mentioned above is necessary. Sometimes it cannot be done immediately.

In such a case, as mentioned above, the fluoride contained in the dust adhering to the inner surface of the window member reacts with moisture in the atmosphere to generate hydrofluoric acid, and the window member is coated with the hydrofluoric acid. In some cases, the anti-reflection coating may be damaged, rendering the window member unusable.

(Problems to be Solved by the Invention) As described above, in conventional gas laser devices, when the window member removed from the laser container cannot be cleaned immediately, dust adhering to the inner surface of the window member reacts with moisture in the atmosphere.
The anti-reflection coating on its inner surface could be damaged.

This invention was made in view of the above circumstances, and its purpose is to prevent the inner surface from being exposed to the atmosphere and being damaged even if the window member removed from the laser container is left for a long time. An object of the present invention is to provide a gas laser device that avoids the above problems.

[Structure of the Invention (Means and Effects for Solving the Problems) In order to solve the above problems, the present invention provides a laser container containing a gas laser medium, a main electrode provided in the laser container, and the laser Openings formed on both axial end faces of the container are formed in a hollow shape through which laser light generated within the laser container passes, and one end side is hermetically joined to a portion of the laser container facing the opening. a holder that is removably installed, a window member airtightly and removably provided on the other end of the holder, and a window member that is rotatably provided inside the holder and faces the inner surface of the window member. and a shutter that, when rotated, seals off a portion of the inner space of the holder on the inner surface side of the window member.

According to such a configuration, if the shutter is rotated to face the window member and the window member is removed from the laser container together with the holder, the window member remains covered with dust for a long time without being cleaned. Even if left unattended, the inner surface with dust attached can be prevented from coming into contact with the atmosphere.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 3 shows a KrF excimer laser as a gas laser device, and this excimer laser is equipped with a laser container 1 in which a gas laser medium containing krypton, fluorine, and helium is sealed at a pressure higher than atmospheric pressure. Openings 2 are formed in the end walls 1a at both axial ends of the laser container 1, and each opening 2 has a window member 3.
A holder 4 provided thereon is attached airtightly and removably as will be described later. A high-reflection mirror 5 is disposed to face one window member 3, and an output mirror 6, which forms an optical resonator with the high-reflection mirror 5, is disposed to face the other window member 3. There is.

Inside the laser container 1, there is a pair of main electrodes 7 or the laser container 1.
They are arranged facing each other and spaced apart in a direction perpendicular to the axial direction of the. These main electrodes 7 are connected to a high voltage power source (not shown). When electrical energy is supplied from this high-voltage power source to the main electrodes 7, a glow discharge occurs between the main electrodes 7, and the gas laser medium is excited, thereby generating laser light.

The laser beam generated in this way is transmitted to the high reflection mirror 5.
The light is repeatedly reflected by the output mirror 6 and amplified, and when it reaches a predetermined intensity, it is oscillated from the output mirror 6.

As shown in FIG. 1, the holder 4 has a collar 1 at the end in the axial direction.
Cylindrical shape with 1 formed - formed. A plurality of mounting holes 13 are formed in the collar 11 at predetermined intervals in the circumferential direction, and an O-ring 14 is provided on the surface to be joined to the laser container 1. Then, the screw 15 is inserted into the mounting hole 13 drilled in the collar 11 of the holder 4.
By screwing this screw 15 into the end wall 1a of the laser container 1, the laser container 1 is airtightly attached.

Inside the holder 4, a large diameter portion 16a is formed at one end, and a small diameter portion 16 communicating with the large diameter portion 16a is formed at the other end.
b is formed. The large diameter portion 16a and the small diameter portion 16b
A mounting shaft 17 is attached along the radial direction of the holder 4 at the boundary between the
is provided.

This mounting shaft 17 is rotatable, and can also be fixed unrotatably by a stopper mechanism (not shown). Further, one end of the first shutter 18 is fixed to the mounting shaft 17. This first shutter 1
8 can be rotated by the mounting shaft 17 from a lying position shown by a solid line in FIG. 1 to an upright position shown by a chain line. When the first shutter 18 is raised,
One of the plate surfaces comes into close contact with the O-ring 2 provided at the interface 19 between the large diameter section 16a and the small diameter section 16b, and can airtightly close one end side of the small diameter section 16b. ing.

A recess 22 is formed on the other end surface of the holder 4 on the small diameter portion 16b side. The window member 3 is provided in this recess 22. This window member 3 has an inner surface fitted with an O-ring 2 provided in the recess 22, and an outer surface pressed against the flange 2.
It is held and provided by 4. Therefore, the small diameter portion 16b of the holder 4 can be airtightly closed by the shutter 18 and the window member 3 by rotating the first shutter 18 in the upright direction.

The holder 4 is connected to an exhaust pipe 25 whose one end communicates with the small diameter portion 16b and which is provided with an on-off valve 25a in the middle. The other end of the exhaust pipe 25 is detachably connected to a vacuum pump (not shown), so that the small diameter portion 16b, which is sealed by the first shutter 18 and the window member 3, can be evacuated.

On the other hand, the opening 2 formed in the laser container 1 can be opened and closed by a second shutter 26 shown in FIG. That is, in the end wall 1a of the laser container 1 where the opening 2 is formed, the slide groove 28 is formed to penetrate in the radial direction. The second shutter 26 is slidably inserted into the slide groove 28 in an airtight manner by means of a pair of O-rings 29 that contact both surfaces of the second shutter 26 . This second shutter 26 has a through hole 31 that is slightly smaller than the opening 2 described above. In addition, the end wall 1a
There are L-shaped brackets 3 on the outer surface of both radial ends of the
2 is provided with one end fixed. Each bracket 32
A presser foot 33 is screwed onto the other end. The tip of each presser foot 33 is in contact with both end surfaces of the second shutter 26 .

Therefore, by turning one presser screw 33 in the backward direction and turning the other presser screw 33 in the forward direction, the second shutter 26 can be slid along the slide groove 28.

As shown in FIG. 2, when the through hole 31 of the second shutter 26 faces the opening 2 of the laser container 1, the laser light generated within the laser container 1 passes through the through hole 31 of the window member. 3 and enters the high reflection mirror 5 or output mirror 6 facing the window member 3. From this state, the second
If the shutter 26 is slid in the direction of the arrow to a position where the through hole 31 is not facing the opening 2, the opening 2 is closed by the second shutter 26.

In other words, the laser container 1 is
Openings 2 formed on both end faces of the can be opened and closed.

In order to oscillate laser light with the excimer laser configured in this way, electrical energy is supplied to the main electrode 7 while facing the through hole 31 of the second shutter 26 or the opening 2 formed in the laser container 1. do. As a result, a glow discharge is generated in the main electrode 7, and the gas laser medium is excited by the glow discharge to generate laser light. This laser light is repeatedly reflected between the high reflection mirror 5 and the output mirror 6 forming an optical resonator, is amplified, and is oscillated from the output mirror 6.

If such operation is repeated for a long time, dust such as discharge products will adhere to the inner surface of the window member 3, so the window member 3 must be removed and cleaned. If the removed window member 3 cannot be cleaned immediately, first clean the mounting shaft 17.
is operated to rotate the first shutter 18 from the collapsed state shown by the solid line in FIG. Seal with 3. Next, the on-off valve 25a of the exhaust pipe 25 is opened to create a vacuum in the sealed small diameter portion 16b, and in this state, the on-off valve 25a is closed to remove the exhaust pipe 25 from the vacuum pump. Thereby, the first shutter 26 and the interface 19
Since the degree of close contact with the O-ring 21 provided in the small diameter portion 16b is increased, the vacuum state within the small diameter portion 16b is reliably maintained.

After the small diameter portion 16b is sealed in this manner, the second shutter 26 is slid in the direction shown by the arrow in FIG. 2 to close the opening 2 of the laser container 1. Next, loosen the screws 15 that attached the holder 4 to the laser container 1, and remove the holder 4.
Remove from airtight container 1.

If the window member 3 is removed from the laser container 1 together with the holder 4 in this way, even if the window member 3 cannot be cleaned immediately, dust attached to its inner surface can be prevented from coming into contact with the atmosphere. .

Therefore, even if the dust adhering to the window member 3 contains fluoride, the fluoride will not react with moisture in the atmosphere to produce hydrofluoric acid, so the window member 3 is coated. It can prevent the anti-reflective coating from being damaged. When cleaning the window member 3 that has been removed together with the holder 4, open the on-off valve 25a provided in the exhaust pipe 25, remove the presser flange 24 from the holder 4, and disassemble the window member 3 from the holder 4. Just go.

When the holder 4 is removed from the laser container 1, the opening 2 formed in the laser container 1 is closed by the second shutter 26, so even if the holder 4 is removed, the gas laser medium in the laser container 1 is not exposed to the outside. There is no leakage.

Note that this invention is not limited to the above-mentioned embodiment, and can be modified in various ways. For example, when the holder 4 is removed from the laser container 1, the small diameter portion 16b sealed by the first shutter 18 is evacuated, but instead it is filled with a non-corrosive dry gas such as nitrogen or helium. Good too.

Further, by preparing a plurality of holders 4 to which window members 3 are attached, the downtime of the gas laser device during maintenance can be shortened.

[Effects of the Invention] As described above, in the present invention, the window member is removed from the laser container along with the holder, and at that time, the holder is removed using a shutter to prevent the dusty inner surface of the window member from coming into contact with the atmosphere. The interior space can now be sealed.

Therefore, even if the dust adhering to the window material contains fluoride, the fluoride reacts with moisture in the atmosphere to produce hydrofluoric acid, and the reflective coating on the window material The barrier film is not damaged. In other words, even if the window member cannot be cleaned immediately after being removed from the laser container, the window member will not be damaged.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is an enlarged cross-sectional view of the holder, FIG. 2 is a cross-sectional view of the end wall of the laser container taken along the line ■-■ in FIG. 1, and FIG. 1 is an overall configuration diagram of a gas laser device. DESCRIPTION OF SYMBOLS 1...Laser container, 2...Opening part, 3...Window member,...Holder, 7...Main electrode, 8...First shutter. Out-of-town agent

Claims (1)

[Claims] A laser container containing a gas laser medium, a main electrode provided in the laser container, openings formed on both axial end faces of the laser container, and a hollow space through which the laser light generated in the laser container passes. a holder formed in a shape and removably provided with one end hermetically joined to a portion facing the opening, a window member airtightly and removably provided on the other end of the holder, and the holder The shutter is rotatably provided inside the holder and is rotated to face the inner surface of the window member, thereby sealing a portion of the inner space of the holder on the inner surface side of the window member. gas laser equipment.