JP2006229137A - Pulse oscillation type discharge pumped laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas laser device for guiding laser gas at a desired flow rate between electrodes to a discharge space stably, reducing the influence of acoustic waves generated in main discharge, especially the influence of acoustic wave components in a discharge direction, and improving the frequency characteristics of laser performance, such as spectrum line width. <P>SOLUTION: The pulse oscillation type discharge pumped laser device for applying a high voltage between main electrodes comprising a pair of anode and cathode electrodes arranged opposingly each other for main pulsive discharge and performing pulse oscillation at a maximum oscillation frequency of 4 kHz or higher has a sound absorbing material that is provided without any gap between the discharge surfaces of at least either the anode electrode or the cathode electrode or is provided in the discharge space with a gap to the discharge surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pulse oscillation type discharge excitation laser apparatus such as an ArF excimer laser, a KrF excimer laser, or an F2 laser, and particularly to reduce the influence of acoustic waves generated by discharge on the generation of laser light and the laser output. .

  With the miniaturization and high integration of semiconductor integrated circuits, there is a demand for improvement in resolution in a semiconductor substrate exposure apparatus. For this reason, the wavelength of the exposure light emitted from the exposure light source is being shortened. As a light source for semiconductor exposure, a gas laser device that emits light having a shorter wavelength than light emitted by a conventional mercury lamp is used. Currently, a KrF excimer laser device that emits ultraviolet light with a wavelength of 248 nm and an ArF excimer laser device that emits ultraviolet light with a wavelength of 193 nm are used as gas laser devices for exposure. As a next-generation exposure gas laser apparatus, a fluorine molecule (F2) laser apparatus that emits ultraviolet light having a wavelength of 157 nm is prominent.

  In the KrF excimer laser device, a mixed gas composed of a fluorine molecule (F2) gas and a krypton (Kr) gas as a laser gas that is a laser medium and a rare gas such as neon (Ne) as a buffer gas is used. In the ArF excimer laser device, a mixed gas composed of a fluorine gas (F2) gas and an argon (Ar) gas as a laser gas which is a laser medium, and a rare gas such as neon (Ne) as a buffer gas is used. In the F2 laser device, a mixed gas composed of a fluorine molecule (F2) gas as a laser gas that is a laser medium and a rare gas such as helium (He) or neon (Ne) as a buffer gas is used. Usually, the laser gas is used by being sealed in a laser chamber at several hundred kPa.

(Configuration and operation of gas laser device)
FIG. 1 is a diagram showing a configuration example of a gas laser apparatus.
A laser gas is sealed inside the laser chamber 12, and a pair of main electrodes 14 and 15 including an anode 14 and a cathode 15 for exciting the laser gas are provided. The anode 14 and the cathode 15 are arranged such that their longitudinal directions are parallel to the laser oscillation direction, their discharge surfaces face each other, and are separated from each other by a predetermined distance. In FIG. 1, the anode 14 and the cathode 15 are arranged in a direction orthogonal to the paper surface. A high voltage pulse is applied between the main electrodes 14 and 15 (between the anode 14 and the cathode 15) by a high voltage power source 23. When the voltage reaches a certain value (breakdown voltage), the laser gas between the main electrodes 14 and 15 breaks down and main discharge is started. Laser gas is excited by this main discharge, and fluorescence that causes laser oscillation is generated. In the gas laser device, pulse oscillation is performed by repeating main discharge, and the emitted laser light becomes pulse light.

  Although not shown in FIG. 1, preliminary ionization means is provided in the laser chamber 12. Prior to the main discharge, ultraviolet light is emitted from the preionization means toward the laser gas between the main electrodes 14 and 15. Then, the laser gas between the main electrodes 14 and 15 is preionized. The main discharge that occurs later by preionization is stabilized. Further, a CFF (Cross Flow Fan) 24 is provided in the laser chamber 12. During high repetitive oscillation, an ionized substance or the like is generated between the main electrodes 14 and 15 due to the discharge, but the laser gas circulates in the laser chamber by the rotation of the CFF 24. It is removed from between the main electrodes 14 and 15.

  A heat exchanger 13 for cooling is provided in the laser chamber 12. A coolant is caused to flow inside the heat exchanger 13. When the laser gas heated by the discharge circulates in the laser chamber 12, it passes through the heat exchanger 13 and is cooled by the coolant. The heat absorbed by the coolant is discharged outside the laser chamber 12. Further, a gas supply line 61 having a gas supply valve 62 and a gas discharge line 63 having a gas discharge valve 64 and a vacuum pump 65 are connected to the laser chamber 12. Laser gas is supplied to the laser chamber 12 via the gas supply line 61, and the laser gas is discharged from the laser chamber 12 via the gas discharge line 63.

  On the laser optical axis outside the laser chamber 12, an LNM (Line Narrow Module) 71 and an output mirror 75 are provided via the laser chamber 12. The LNM 71 includes one or more beam expanding prisms 72 and a grating 73 that reflects light in a direction corresponding to the wavelength. The fluorescence generated by the main discharge is narrowed while being selected at a predetermined wavelength by the LNM 71, oscillates by reciprocating between the output mirror 75, and is output from the output mirror 75 as laser light. The laser light output from the output mirror 75 enters the beam sampler 76. The beam sampler 76 divides incident laser light into two-way laser light. One laser beam enters the beam monitor 77. The beam monitor 77 measures information such as the energy, stability, and pulse width of the laser pulse. The other laser beam is output to the exposure apparatus side.

  The controller 80 controls the energy and wavelength of the laser pulse based on each information from the beam monitor 77. For example, as one form of wavelength control, the controller 80 outputs a command signal S1 to a grating driving mechanism (not shown) based on wavelength information from the beam monitor 77. In response to the command signal S1, the grating driving mechanism adjusts the attitude of the grating 73 and controls the incident angle of the laser beam to the grating 73. As one form of energy control, the controller 80 outputs a command signal S2 to the high voltage power supply 23 based on energy information from the beam monitor 77. The high voltage power supply 23 controls the voltage applied to the main electrodes 14 and 15 in response to the command signal S2. As another form of energy control, the controller 80 outputs command signals S3, S4, and S5 to the gas supply valve 62, the gas discharge valve 64, and the vacuum pump 65 based on the energy information from the beam monitor 77. In response to the command signals S3, S4, and S5, the gas supply valve 62 and the gas discharge valve 64 are opened and closed, and the vacuum pump evacuates the laser chamber 12 so that the mixing ratio and pressure of the laser gas in the laser chamber 12 are adjusted. Control.

(High output of gas laser equipment)
In recent years, there is a tendency that further higher output and narrower band are required for the gas laser apparatus for exposure. This tendency seems to be more remarkable in the ArF excimer laser. The main reasons are that the resist used for exposure with ArF excimer laser is less sensitive than the resist used for exposure with KrF excimer laser, and there is a demand for high throughput and high resolution. , Etc. are raised.

  Two methods are conceivable for realizing high output of the gas laser device. One is to increase the energy per pulse. In this method, it is not necessary to increase the oscillation frequency, but since the peak power in the laser pulse increases, there is a concern about damage to the optical system. In order to increase the energy per pulse while suppressing the increase in peak power, it is necessary to perform pulse stretching so as to extend the laser oscillation time in terms of time. However, there are trade-offs between oscillation time and energy, and pulse stretching is performed electrically or optically, so that the device itself is complicated. The other is to increase the oscillation frequency. In this method, since it is not necessary to increase the energy per pulse, the damage to the optical system is not so great. However, as the oscillation frequency is increased, the influence of the acoustic wave generated by the discharge increases. As will be described later, acoustic waves are closely related to narrowing the band.

  In order to obtain stable laser oscillation by increasing the oscillation frequency, it is necessary to increase the circulation flow rate between the main electrodes, and it is necessary to increase the power consumption in the motor of the CFF 24.

(Acoustic wave)
When the oscillation frequency is low, the acoustic wave generated in the previous discharge is attenuated until the next discharge, so that there is no problem. However, when the oscillation frequency is high, the acoustic wave generated in the previous discharge is not sufficiently attenuated until the next discharge. This phenomenon becomes remarkable particularly at an oscillation frequency exceeding 2 kHz. The acoustic wave causes the laser gas to become sparse and dense. Therefore, if an acoustic wave exists between the main electrodes 14 and 15 at the time of the next discharge, the laser gas between the main electrodes 14 and 15 becomes dense. Therefore, a change in refractive index appears in a direction (discharge direction and discharge width direction) orthogonal to the laser optical axis direction, and the gain is not uniform. The change in the refractive index causes distortion in the wavefront of the laser beam. When the wavefront of the laser light is distorted, the LNM 71 does not function normally, and the spectral line width does not become constant.

  The specifications required for the current excimer laser for exposure are that the maximum value of the pulse repetition number is 4 kHz or more and the spectrum line width is 0.2 pm or less.

  FIG. 2 is a diagram showing the relationship between the oscillation frequency and the spectral line width when affected by an acoustic wave.

  In FIG. 2, the minimum value of the spectral line width is about 0.2 pm, and the fluctuation width of the spectral line width is about 0.12 pm at the maximum. It is difficult to satisfy the specification value of the spectral line width of 0.2 pm or less. In addition, laser performance (beam pointing, beam size, etc.) other than the spectral line width is also affected by acoustic waves. Therefore, when the gas laser device is used at a high oscillation frequency, a method for reducing the influence of acoustic waves is essential.

  FIG. 3 is a schematic diagram for explaining how the acoustic wave generated by the main discharge propagates.

  In FIG. 3, the main electrodes 14 and 15 are arranged to face each other. When the CFF 24 operates, the laser gas recirculates in the laser chamber 12 and flows in the discharge space 37 from the left side (hereinafter referred to as upstream) to the right side (hereinafter referred to as downstream) in the drawing. When a high voltage is applied to the main electrode and main discharge occurs, an acoustic wave is generated in the discharge space 37.

  As shown in FIG. 3, the acoustic wave generated in the main discharge is divided into acoustic wave components that propagate in the discharge width direction (X-axis direction), the longitudinal direction (Y-axis direction), and the discharge direction (Z-axis direction). . The acoustic wave propagated to the space is reflected by surrounding members, and a part of the reflected acoustic wave returns to the discharge space 37 again.

  It is the acoustic wave components in the X-axis direction and the Z-axis direction among the acoustic wave components reflected and returned to the discharge space 37 that have a large influence on the laser performance. On the other hand, it is considered that the acoustic wave component in the Y-axis direction does not significantly affect the laser performance. The laser beam profile (intensity distribution) is obtained by integrating the intensity distribution on a plane (XZ axis wavefront) perpendicular to the laser optical axis in the laser optical axis direction (Y-axis direction). Therefore, even if the density distribution of the laser gas in the Y-axis direction is generated by the acoustic wave component in the Y-axis direction, various density distributions are integrated and homogenized.

  Therefore, in order to cope with the above problem, Patent Document 1 below discloses an apparatus in which a pleated portion having unevenness is provided in the vicinity of the main electrode, and an attenuation material for attenuating an acoustic wave generated by the main discharge is inserted into the recessed portion. Yes.

Further, in Patent Document 2 below, an acoustic wave generated in the previous discharge and propagated to the space is separated from the discharge space by a predetermined distance so as not to be reflected in the discharge space before the next discharge starts. An apparatus is disclosed in which no member that reflects acoustic waves in the direction of the discharge space is disposed within the range.
JP 2003-60270 A JP 2003-298155 A

  In the case of Patent Document 1, although there is an effect of reducing the acoustic wave component in the Z-axis direction, the laser gas flow is disturbed by a member having an uneven fold portion arranged in the vicinity of the main electrode, and a desired interelectrode flow velocity is obtained. The laser gas cannot be stably guided to the discharge space 37.

  According to Patent Document 2, the influence of the acoustic wave component propagating in the X-axis direction can be reduced, but the effect of reducing the influence of the acoustic wave component propagating in the Z-axis direction is that the oscillation frequency is 4 kHz. The range exceeding this is not necessarily sufficient.

  According to the inventors of the present application and the like, in the case of a gas laser device having a maximum oscillation frequency of 4 kHz or more, which is the subject of the present invention, it has been clarified that an acoustic wave component in the Z-axis direction has a large effect on laser performance. That is, in the case of Patent Document 1, the reflection surface of the member arranged in the Z-axis direction is close to the main electrodes 14 and 15, and the acoustic wave component in the Z-axis direction is difficult to escape from the discharge space 37 and is reflected for a long time. There is a problem of repeatedly staying.

  Therefore, in order to solve the above problem, the structure around the main electrode is changed so that the acoustic wave component in the Z-axis direction can quickly escape from the discharge space, or the acoustic energy of the acoustic wave component in the Z-axis direction is attenuated. It is necessary to let At that time, the acoustic wave component in the X-axis direction needs to be set to the level described in Patent Document 1 or less in the range of the high oscillation frequency of 4 kHz or higher, and the acoustic wave component in the Z-axis direction is further reduced. There is a need.

  The present invention has been made in view of the above-described problems, and can stably guide a laser gas having a desired interelectrode flow velocity into the discharge space, and also influence the acoustic waves generated by the main discharge, particularly the acoustic in the discharge direction. An object of the present invention is to provide a gas laser device that can reduce the influence of wave components and improve the frequency characteristics of laser performance such as spectral line width.

  In order to achieve the above object, the first invention performs a pulsed main discharge by applying a high voltage between main electrodes including a pair of anode electrodes and a cathode electrode arranged to face each other. In the pulse oscillation type discharge excitation laser apparatus that oscillates at a maximum oscillation frequency of 4 kHz or more, it is provided without opening a gap between at least the discharge surface of one of the anode electrode and the cathode electrode, or In the discharge space, a sound absorbing material provided with a gap between the discharge surface and the discharge surface is provided.

  In the second invention, a high voltage is applied between a pair of anode electrodes and cathode electrodes arranged opposite to each other to perform pulsed main discharge, and pulse oscillation with a maximum oscillation frequency of 4 kHz or more is performed. In the pulse oscillation type discharge excitation laser device, at least one of the anode electrode and the cathode electrode is formed with a hole or groove penetrating from the discharge surface to the back surface side, and the hole or groove is formed on the back surface side. It is characterized in that a sound absorbing material is provided corresponding to the position.

  In the third aspect of the invention, a high voltage is applied between a pair of anode electrodes and cathode electrodes arranged opposite to each other to perform pulsed main discharge, and pulse oscillation with a maximum oscillation frequency of 4 kHz or more is performed. In the pulse oscillation type discharge excitation laser device, a hole or groove penetrating from the discharge surface to the back surface side of at least one of the anode electrode and the cathode electrode is formed, and a sound absorbing material is provided in the hole or groove. It is characterized by being.

  According to a fourth invention, in any one of the first to third inventions, the sound absorbing material is a ceramic material.

  According to the first invention, as shown in FIG. 21, the acoustic wave energy in the Z-axis direction of the discharge space can be attenuated by the sound-absorbing material formed at the upper part of the discharge surface, and the Z-axis direction of the discharge space with respect to the laser performance can be attenuated. The influence of acoustic wave components can be reduced.

  According to the second invention, as shown in FIG. 22, the acoustic wave energy in the Z-axis direction that has passed through the through-hole can be attenuated by the sound absorbing material disposed on the back surface facing the discharge surface, and the laser performance The influence of the acoustic wave component in the Z-axis direction of the discharge space can be reduced.

  According to the third invention, as shown in FIG. 26, the acoustic wave energy in the Z-axis direction that has passed through the gap can be attenuated by the sound-absorbing material disposed on the back surface facing the discharge surface. The influence of the acoustic wave component in the Z-axis direction of the discharge space can be reduced.

  According to the fourth aspect of the present invention, there is no possibility that the sound absorbing performance of the sound absorbing material is deteriorated by fluorination and sputtering, so that stable laser performance can be obtained for a long time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Structure inside the laser chamber)
FIG. 4 is a diagram showing the configuration of the gas laser device according to the embodiment of the present invention, and FIG. 5 is a diagram showing the vicinity of the main electrode. 4 and 5 correspond to the cross-sectional view of the laser chamber shown in FIG. Hereinafter, description will be made with reference to FIGS. 4 and 5 together. For convenience, the vertical direction of the drawing will be described as the vertical direction of the apparatus. The discharge direction is the Z-axis direction, the longitudinal direction is the Y-axis direction, and the discharge width direction is the X-axis direction.

  Laser gas is sealed in the laser chamber 12 at a predetermined pressure. Also, a pair of main electrodes 14 and 15, each consisting of a metal anode 14 and a cathode 15, are installed inside the laser chamber 12 so as to face each other in the vertical direction with the discharge space 37 interposed therebetween. When a high voltage is applied between the main electrodes 14 and 15 from the high voltage power supply 23, a pulsed main discharge is generated in the discharge space 37. Then, the laser gas is excited, and a pulsed laser beam is generated in a direction perpendicular to the paper surface of FIG.

  Inside the laser chamber 12, a CFF 24 that circulates the laser gas inside the laser chamber 12 and sends it to the discharge space 37, and a heat exchanger 13 that cools the laser gas heated by the discharge are installed at predetermined positions. ing. The surfaces of the cathode insulating member 54 and the anode insulating members 55 and 58 facing the laser gas flow path are laser gas flow path wall surfaces. As represented by the arrow 47 in FIG. 4, the gas flow of the laser gas flows from the upstream (left side in the figure) to the downstream (right side in the figure) so as to cross the discharge space 37. In the gas laser apparatus, high-speed laser gas is induced between the main electrodes, and therefore, the surface of the member around the discharge portion including the main electrode forms a laser gas flow path W.

  A chamber opening 35 is provided in the upper part of the laser chamber 12. The chamber opening 35 is closed by a cathode base 36 made of an insulator such as ceramic. The cathode base 36 is pressed upward inside the laser chamber 12 by a cathode base presser 46 and is fixed by a fixing bolt (not shown). An O-ring 52 is disposed between the laser chamber 12 and the cathode base 36, and laser gas is sealed inside the laser chamber 12.

  The cathode 15 is fixed to the lower surface of the cathode base 36. The cathode 15 includes a rod-like support portion 15A having a curvature at a corner, and a plate-like discharge portion 15B having a width of about 2 to 5 mm projecting about several millimeters at a substantially central portion of the support portion 15A. 4 and 5 show a configuration in which the support portion 15A and the discharge portion 15B are integrated, the discharge portion 15B may be fixed to the support portion 15A with screws or the like. .

  The cathode 15 and the laser chamber 12 are electrically insulated by a cathode base 36. The cathode base 36 is provided with a plurality of high-voltage power supply rods 48 that penetrate the cathode base 36 in the vertical direction and reach the cathode 15 at predetermined intervals along the electrode longitudinal direction. The high voltage power supply rod 48 is connected to the high voltage side HV of the high voltage power supply 23 through a discharge circuit (not shown). A high voltage current is supplied to the cathode 15 by the high voltage power supply rod 48. A space between the high-voltage power supply rod 48 and the cathode base 36 is sealed with an O-ring 53.

  A cathode insulating member 54 made of alumina ceramic or the like is installed on the upstream side and the downstream side of the cathode 15. The cathode insulating member 54 is fixed to the lower surface of the cathode base 36 with a bolt or the like (not shown). The surfaces of the upstream and downstream cathode insulating members 54 are inclined downward toward the cathode 15 side so that the laser gas flow path is closer to the cathode 15 side. Therefore, the flow path of the laser gas gradually expands as the discharge space 37 is the narrowest and goes upstream and downstream. Further, since the cathode insulating member 54 covers the support portion 15A of the cathode 15, the spread of the electric field distribution is suppressed and the main discharge is stabilized. This is because the equipotential surface is relatively parallel to the left and right of the cathode 15 as compared with the case where there is no support portion 15A. The discharge part 15B has a protruding part 15C protruding from the cathode insulating member 54 to the discharge space 37 side by about 1 to 3 mm. The tip of the protruding portion 15C becomes the discharge surface (see FIG. 5).

  The anode 14 facing the cathode 15 is formed of a plate-like metal having a width of about 2 to 5 mm. The anode fixing screw 43 passes through the anode retainer 44 and the anode 14 and is screwed into the anode holder 42. Then, the anode 14 is sandwiched and fixed between the anode retainer 44 and the anode holder 42. The anode holder 42 and the anode retainer 44 are made of metal. The anode holder 42 is installed on a metal anode base.

  On the upstream and downstream sides of the discharge space 37, a plurality of plate-like return plates 39 having a width of several millimeters (for example, about 1 mm) are installed at predetermined intervals along the main electrode longitudinal direction (vertical direction in the drawing). Yes. The upper part of the return plate 39 is fixed to the cathode base presser 46 with a return plate fixing screw 56. The lower portion of the return plate 39 is fixed to the anode holder 42 by a return plate fixing screw 56. The laser chamber 12 is connected to the ground side GND of the high-voltage power supply 23 through a discharge circuit (not shown), and has a ground potential. The anode 14, the anode holder 42, the anode holder 44, and the anode base 40 are electrically connected to the laser chamber 12 by a return plate 39 and are at ground potential. Since the return plate 39 is thin, it does not affect the gas flow 47 of the laser gas.

  A first anode insulating member 55 and a second anode insulating member 58 are installed on the upstream side and the downstream side of the anode 14. The surfaces of the upstream and downstream anode insulating members 55 and 58 are inclined upwardly toward the anode 14 side so that the laser gas flow path becomes closer to the anode 14 side. The upper end portion of the anode 14 has a protruding portion 14E that protrudes from the anode insulating member 55 to the discharge space 37 by a predetermined length. The tip of the protrusion 14E becomes a discharge surface (see FIG. 5).

  On the upstream side and the downstream side of the second anode insulating member 58, guides 59 for guiding the gas flow 47 of the laser gas are respectively installed. The guide material is a fluorine-resistant metal or ceramic. Further, since the anode 14 and the laser chamber 12 are at the same potential (ground potential), the material of the anode insulating members 55 and 58 is not necessarily an insulator. However, since the anode insulating members 55 and 58 on the downstream side are insulators, occurrence of arc discharge is prevented when the flow rate of the laser gas is insufficient on the downstream side of the discharge space 37. Further, since the upstream anode insulating members 55 and 58 are insulators, the spread of the electric field distribution is suppressed and the main discharge is stabilized.

  The surface of the first anode insulating member 55 and the surface of the second anode insulating member 58 are inclined to the same extent. The two surfaces are in contact with each other so that the surfaces are included in substantially the same plane, and there is no gap between the two except for the portion where the return plate 39 is interposed. There is an appropriate range for the spread angle formed by the first anode insulating member 55, the second anode insulating member 58, and the cathode insulating member 54. For example, when both are parallel, the acoustic wave 41 becomes a standing wave between the insulating members 54, 55, and 58, and it takes a long time to attenuate. In addition, if the angle of spread is too large, pressure loss occurs in the laser gas flow, leading to a decrease in flow velocity and turbulence. For this reason, the main discharge may be disturbed.

  The upstream second anode insulating member 58 is provided with a preionization electrode 38 composed of a metal columnar inner conductor 38A and a cylindrical dielectric 38B surrounding the peripheral surface thereof. It is buried almost parallel to the direction. Note that a part of the outer peripheral surface of the preionization electrode 38 protrudes from the second anode insulating member 58 and is exposed to the laser gas flow path. The internal conductor 38A is electrically connected to the high voltage side HV of the high voltage power supply 23. One end of the external auxiliary electrode 57 made of a metal plate is fixed to the lower end portion of the upstream return plate 39 by a return plate fixing screw 56. The other end of the external preliminary electrode 57 is disposed along the surface of the second anode insulating member 58, and the tip is in contact with the dielectric 38 </ b> B of the preliminary ionization electrode 38. The external auxiliary electrode 57 is at a ground potential, similar to the laser chamber 12. When a high voltage is applied from the high voltage power supply 23 between the high voltage side HV and the ground side GND, a corona discharge occurs between the external spare electrode 57 and the internal conductor 38A, and the discharge space 37 is preionized. . Then, main discharge is likely to occur between the main electrodes 14 and 15. When main discharge is generated between the main electrodes 14 and 15, laser light is generated.

  Accompanying the main discharge, an acoustic wave 41 is generated from the discharge space 37. The acoustic wave 41 propagates to the entire space and is reflected by surrounding members, and a part of the reflected acoustic wave returns to the discharge space 37 again.

  In order to stably induce a laser gas having a desired inter-electrode flow velocity and allow the acoustic wave component in the Z-axis direction to escape immediately from the discharge space, the surfaces of the main electrode and the members disposed in the vicinity thereof The laser gas flow path constructed with the above structure is made smooth and the inclination angle of the laser gas flow path wall surface is increased, and the propagating acoustic wave component in the Z-axis direction is reflected outside the discharge space by the reflection surface having a large inclination angle. You can do it.

  FIG. 6 is a schematic diagram for explaining the inclination angle of the smooth laser gas flow path W. FIG.

  In FIG. 6, the wall surfaces 6A and 6B, which are connected to the side surfaces of the main electrodes 14 and 15, specifically, the surfaces of the insulating members 54, 55, 58, etc., are spread out to the outside of the main electrode in the X-axis direction. Has an inclined surface with an inclination angle of θ. The acoustic wave component in the Z-axis direction propagated to the laser gas flow path W is reflected in a direction further away from the discharge space 37 corresponding to the inclination angle θ.

  FIG. 7 is a schematic diagram showing a case where the wall surfaces 7A and 7B are formed at an inclination angle θ ′ larger than the inclination angle θ of FIG. In this case, the acoustic wave component in the Z-axis direction can easily escape from the discharge space 37 more quickly. However, if the tilt angle is too large, the pressure loss increases and the inter-electrode flow velocity decreases, so the tilt angle has a limit.

  The reflection related to the stay of the acoustic wave component in the Z-axis direction is considered to be largely influenced by the reflection from the member in the vicinity of the side surface of the main electrode, particularly in the region of the distance of the wavelength of the acoustic wave with respect to the X-axis direction. . Therefore, in order to quickly reduce the acoustic wave component in the Z-axis direction from the discharge space with almost no decrease in the interelectrode flow velocity, the inclined surface has a steep angle only in a minute region of the laser gas flow path near the main electrode. And the acoustic wave component in the Z-axis direction may be reflected to the outside of the discharge space by this inclined surface.

  Therefore, the first embodiment according to the present invention includes a main electrode composed of a pair of anode and cathode electrodes arranged to face each other, and a laser gas flow path including the main electrode, and the gap between the main electrodes. In a pulsed discharge-type excitation laser apparatus that performs pulsed main discharge by applying a high voltage and has a maximum oscillation frequency of 4 kHz or higher, particularly 6 kHz or higher, at least near the discharge surface of one of the main electrodes An inclined surface is formed on the wall surface of the laser gas flow path to reflect the component in the discharge direction of the acoustic wave generated by the main discharge to the outside of the discharge space.

  FIG. 8 is a schematic cross-sectional view in the vicinity of an electrode for explaining the laser gas flow path W having a two-step inclination angle. Connected to both side surfaces of the main electrodes 14 and 15, laser gas flow paths W each formed by an inclined surface 8A having a large inclination angle and a wall surface 8B having a normal inclination angle are formed. The region where the inclined surface 8A is formed is a predetermined range in the laser gas flow path W from the boundary (electrode side surface 8C) between the discharge surface and the non-discharge surface to the outside of the electrode.

  FIGS. 9A and 9B are configuration diagrams of two types of laser gas flow paths W used for simulation comparison of sound pressure between main electrodes.

  FIG. 9A shows a conventional one-stage inclined laser gas passage having an inclination angle, and the laser gas passage W has a wall surface 9A having a constant inclination angle (here, 5.6 degrees) and has a main electrode 15. It is connected to the side. FIG. 9B is a two-stage inclined laser gas flow channel according to the present invention. The laser gas flow channel W is formed by an inclined surface 9B having a large inclination angle (about 23 degrees) connected to the main electrode, and an inclined surface 9B. The wall surface 9C is connected and has an inclination angle (5.6 degrees) that does not cause too much pressure loss. The inclined surface 9B is connected to the side surface of the main electrode 15 and is formed within a range of 1.5 mm in the X-axis direction and 0.65 mm in the Z-axis direction from the connection position of the side surface of the main electrode with this point as the base point. The

  FIG. 10 is a comparison diagram showing the result of simulation calculation of the effective value of the sound pressure between the main electrodes. In the simulation, the laser gas flow paths W composed of the surfaces of the insulating members 54, 55, 58 and the like shown in FIG. 9A or 9B are arranged upstream and downstream on the main electrodes 14, 15 side, respectively. Performed under the same conditions. The horizontal axis represents the elapsed time since the occurrence of discharge, and the vertical axis represents the sound pressure of the generated acoustic wave.

  The excimer laser currently used has a maximum oscillation frequency of 4 kHz, and the oscillation interval at that time is 250 μs. In FIG. 10, it can be seen that the acoustic wave energy staying between the main electrodes of the two-step tilt model is about 60% in the vicinity of the elapsed time of 250 μs as compared with the case of the one-step tilt model. In addition, the two-stage tilt model has an inclined surface with a large tilt angle, but if it is such a narrow region, it hardly affects the flow velocity between electrodes.

  In the above-described simulation, the inclined surfaces are provided on both the main electrodes 14 and 15 side. However, it is effective to quickly release the acoustic wave only by providing the inclined surface on either the main electrode 14 or 15 electrode side. Further, an inclined surface may be provided on the anode electrode and the cathode electrode on either the upstream side or the downstream side. Furthermore, an inclined surface may be provided, for example, every 5 mm instead of the entire region of the main electrode in the longitudinal direction. In this case, it is effective because the acoustic wave component is not uniformly affected in the same time in the laser optical axis direction (longitudinal direction).

  The region where the inclined surface is formed is preferably in the range of 0.5 mm or more from the boundary (electrode side surface) between the discharge surface and the non-discharge surface in the laser gas flow path to the outer side of the electrode. The reason is that in consideration of the wavelength of the acoustic wave, the acoustic wave component in the Z-axis direction cannot be promptly reflected in a minute region below this. The upper limit may be determined by optimizing as appropriate.

  FIG. 11 is a diagram for explaining the relationship between two inclination angles in a laser gas flow path having a two-stage inclination.

  In FIG. 11, the inclined surface 11A has an inclination of an angle θ2 with respect to the discharge width direction, the wall surface 11B has an inclination of an angle θ1 with respect to the discharge width direction, and the angles θ1 and θ2 are 0 ° <θ1. The relationship <θ2 ≦ 45 ° is satisfied.

The larger the angle θ2, the quicker the acoustic wave component in the Z-axis direction can be released, but in practice it is desired to reduce the influence of the acoustic wave on the laser performance by at least 10% compared to the conventional case. Therefore, as a result of performing an acoustic wave simulation based on the laser gas channel structure of FIG.
θ1 + 5 ° ≦ θ2 (1)
It has been found that the effect of the acoustic wave is reduced by 10% or more compared to the conventional case if the above equation is satisfied. Therefore, the shape of the laser gas flow path can be appropriately designed based on the equation (1) obtained by the simulation.

  In the above embodiment, the angle θ2 is not particularly defined, but the range of the angle θ2 is preferably 10 to 30 degrees in order to obtain a desired interelectrode flow rate stably. Moreover, you may form the wall surface after this by two steps or more.

  FIG. 12 is a view for explaining the form of the inclined surface and the wall surface.

  FIG. 12A is a view showing a form in which a two-step slope is formed on the surface of the member 12A disposed on the side surface of the main electrode 15. FIG. That is, the inclined surface 12B and the wall surface 12C are formed on the surface of the member 12A.

  FIG. 12B is a diagram showing a form in which inclined surfaces 12F and wall surfaces 12G are formed on the surfaces of two members 12D and 12E arranged on the side surface of the main electrode 15, respectively.

12A and 12B, the inclined surface or wall surface is formed on the surface of an insulating member or the like, but the electrode itself may be provided with the inclined surface or wall surface.
FIG. 12C is a diagram showing a form in which a two-step inclination is formed on the main electrode itself. An inclined surface 12H and a wall surface 12I are continuously formed on the side surface of the main electrode 15 that is a predetermined distance away from the discharge surface 15D at the tip of the protruding portion 15C of the main electrode 15.

  FIG. 12D is a diagram showing a case where an inclined surface is formed on the main electrode itself. An inclined surface 12J is formed from the side surface of the main electrode 15 that is a predetermined distance away from the discharge surface 15D at the tip of the protruding portion 15C of the main electrode 15. A wall surface 12K made of the member surface is connected to the inclined surface 12J.

  In the above description, the inclined surfaces are all planar. However, the inclined surface does not have to be particularly flat, and may be curved.

  FIG. 13 is a diagram illustrating a case where the inclined surface has a curved surface shape.

  In FIG. 13, inclined surfaces 13A and 13A are formed in regions surrounded by dotted lines, and are connected to wall surfaces 13B and 13B, respectively. In the inclined surfaces 13A and 13A, the inclination of the portions 13C and 13C connected to the side surface of the main electrode 15 is the largest, and the inclination becomes smaller as approaching the wall surfaces 13B and 13B, and finally the inclination angle on the wall surface side. Are connected to the wall surfaces 13B and 13B. That is, the inclined surfaces 13A and 13A are curved.

  In the above description, the side surface of the main electrode has been described as being parallel to the discharge direction. If the main electrode has such a shape, the change in the shape of the laser beam can be reduced even if the discharge surface is shaved by continuous discharge for a long time.

  The side surface of the projecting portion of the main electrode is not necessarily parallel to the Z-axis direction. That is, the side surface of the projecting portion may have a tapered shape that extends to the back surface side.

  FIG. 14 is a diagram showing a case where the side surface of the main electrode 15 has a tapered shape.

  For example, the inclination angle of the side surface 14A with respect to the discharge direction can be set to 0 to 15 degrees. With such an inclination, the change in laser beam size is small even after continuous discharge for a long time. For example, a two-step inclined inclined surface 14C and a wall surface 14D are provided by connecting to the end 14B of the side surface 14A. it can. Also in this case, the inclined surface 14C needs to be formed in a range of 0.5 mm or more from the discharge surface 15D (electrode side surface) to the electrode outer side in the laser gas flow path.

  If the consumption of the main electrode does not matter so much, the inclination angle of the side surface 14A of the main electrode shown in FIG. 14 is further increased, and the acoustic wave component in the Z-axis direction is reflected using the side surface region of the main electrode. It can also be made.

  FIG. 15 is a schematic view of the vicinity of the main electrode when the sound absorbing material is arranged most efficiently in order to attenuate the acoustic energy of the acoustic wave component in the Z-axis direction.

  In FIG. 15, a sound absorbing material K is provided over the entire wall surface of the laser gas channel disposed on both side surfaces of the main electrodes 14 and 15. The surface of the sound absorbing material K facing the discharge space 37 also serves as the laser gas flow path W.

  However, in this case, since the laser gas flow velocity is reduced by the surface resistance of the sound absorbing material K, there is a case where the laser gas having a desired interelectrode flow velocity is prevented from flowing. Further, when the sound absorbing material K is used in a wide area around the main electrode, there is a problem that it is necessary to ensure a dielectric strength voltage against a high voltage. Therefore, when the sound absorbing material K is used, it is necessary to examine the arrangement method of the sound absorbing material and the selection of the material of the sound absorbing material.

  In order to reduce the influence on the interelectrode flow velocity as much as possible and to reduce the influence of the acoustic wave component in the Z-axis direction, it is considered to limit the location where the sound absorbing material is arranged and to optimize the hole diameter, porosity, etc. It is done.

Accordingly, a second embodiment according to the present invention is directed to a main electrode composed of a pair of anode and cathode electrodes arranged to face each other, and a smooth laser gas flow path having no crease between the main electrodes. A pulsed discharge-type pumped laser apparatus that performs pulsed main discharge by applying a high voltage between the electrodes, and oscillates at a maximum oscillation frequency of 4 kHz or more, at least one of the main electrodes A sound absorbing material that absorbs a component in the discharge direction of the acoustic wave generated by the main discharge is provided on the wall surface of the laser gas channel near the discharge surface of the electrode.

  Here, the vicinity of the discharge surface refers to a region from the discharge surface 14D to the position where the preliminary ionization electrode 38 is provided on the main electrode 14 side, and on the main electrode 15 side, the discharge surface of the main electrode 15. A region from 15D to the periphery of the position facing the preionization electrode 38.

  In the following, components having the same functions as those described in the first embodiment will be given the same reference numerals and description thereof will be omitted.

  Of the acoustic waves generated in the discharge space, the problem is that the acoustic wave component in the Z-axis direction stays between the main electrodes, and it is not necessary to attenuate all the acoustic waves generated in the discharge space.

  As shown in FIG. 16, a sound absorbing material may be disposed in the vicinity of the main electrode instead of the inclined surface described in the first embodiment.

  In FIG. 16, the sound absorbing material K is connected to both side surfaces of the main electrodes 14 and 15 to constitute a laser gas flow path W. Even if this is done, there is a great effect in attenuating the acoustic wave component in the Z-axis direction. Since the surface of the sound absorbing material K reduces the laser gas flow velocity between the main electrodes, in order to avoid this as much as possible, the sound absorbing material K is provided from the discharge surface to a predetermined distance L in the X-axis direction. L should be as small as possible. The distance L may be appropriately determined by experiments or the like. In this case, the dielectric strength on the high voltage side (in this case, the main electrode 15 side) is not significantly affected. Therefore, if L is small, the material of the sound absorbing material K may be conductive, but preferably a dielectric. Is good.

  When the sound absorbing material is arranged around the main electrode, the sound absorbing material having a smaller hole diameter and porosity as parameters does not decrease the flow velocity of the laser gas, so it is necessary to determine the parameters of the sound absorbing material in consideration of the necessary sound absorbing rate. There is. Since a high voltage is applied to at least one of the sound absorbing materials (here, the main electrode 15), the material of the sound absorbing material is limited when the sound absorbing material is disposed near the main electrode to which the high voltage is applied. That is, in this case, it is necessary to use a ceramic system (alumina, aluminum nitride, etc.) having a high withstand voltage.

  Conventionally, the electrode component on the high voltage side is held by a member made of ceramics. Therefore, when a ceramic-based sound absorbing material is disposed, it is necessary to affix to this ceramic member. As the method, a screwing method is simple and preferable. At this time, it is desirable to use a ceramic screw as the screw. Furthermore, a member in which a portion having a sound absorbing effect and a dense portion are integrally manufactured can be used.

  By the way, as a member that affects the acoustic wave component in the Z-axis direction, for example, there is a preionization electrode. If the preliminary ionization electrode is separated from the discharge space 37, the influence is reduced. However, the preliminary ionization electrode is necessary for stable main discharge, and it is not preferable to separate the preliminary ionization electrode from the discharge space 37 so much. However, if they are too close, particularly when an oscillation frequency of 4 kHz or higher is targeted, the acoustic wave reflected from the preionization electrode returns to the discharge space 37 and affects the laser performance.

  FIG. 17 is a schematic diagram of a cross-sectional structure of a preionization electrode.

  As shown in FIG. 17, when the outside of the preionization electrode 38 is surrounded by a tube 38B such as alumina and a high voltage is applied to the internal conductor 38A side, corona discharge is generated and ultraviolet light is emitted. Preliminary ionization is caused by the ultraviolet light, and a stable main discharge can be obtained. Therefore, the preliminary ionization electrode 38 is a necessary part for obtaining a stable main discharge. Corona light emission is possible even when the internal conductor 38A side is at ground potential and the outer electrode of the tube 38 is at high voltage.

  FIG. 18 is a schematic view showing a case where a sound absorbing material is provided on the wall surface of the laser gas flow channel other than the main electrode and the preionization electrode in order to reduce the reflection of the preionization electrode.

  In FIG. 18, two preliminary ionization electrodes 38, 38 are provided on the wall surface of the laser gas channel around the main electrode 14. Further, a sound absorbing material K is attached to the laser gas channel wall surface between the preionization electrodes 38 and 38 and the main electrode 14 and outside the preionization electrodes 38 and 38 when viewed from the main electrode 14. Further, the sound absorbing material K is also attached to the entire surface of the laser gas flow channel wall on both sides on the main electrode 15 side.

  In this way, the acoustic wave component reflected on the surfaces of the preliminary ionization electrodes 38 and 38 and propagated in the Z-axis direction can be absorbed by the sound absorbing material K provided on the laser gas channel wall surface on the main electrode 15 side. However, the flow rate of the laser gas is reduced by the surface resistance of the sound absorbing material attached to the entire surface.

  According to the inventors of the present application and the like, it was found from simulation that it is not necessary to arrange the sound absorbing material as shown in FIG.

  FIG. 19 is a schematic diagram showing a sufficient sound absorbing material arrangement obtained from the simulation.

  In FIG. 19A, unlike the case of FIG. 18, the sound absorbing material K is provided only between the main electrode 14 and the preliminary ionization electrodes 38 on the wall surface of the laser gas flow path on the main electrode 14 side.

  In FIG. 19B, unlike the case of FIG. 18, a sound absorbing material is provided only between the main electrode 14 and the preliminary ionization electrodes 38 on the wall surface of the laser gas flow channel on the main electrode 14 side. Further, the sound absorbing material K is provided only in a predetermined region facing the preliminary ionization electrodes 38 on the wall surface of the laser gas channel on the main electrode 15 side.

  In FIG. 19, the sound absorbing material K may be provided only in a predetermined region facing the preionization electrodes 38 and 38 on the wall surface of the laser gas channel on the main electrode 15 side.

  By arranging the sound absorbing material shown in FIG. 19, the acoustic energy reflected in the Z-axis direction can be effectively attenuated without reducing the flow velocity of the laser gas.

  Instead of devising a method of arranging a sound absorbing material that absorbs reflection of acoustic waves by the preliminary ionization electrode 38, the reflection itself by the preliminary ionization electrode 38 may be reduced.

  By reducing the amount of protrusion H that the tube 38B of the preliminary ionization electrode 38 protrudes from the laser gas flow path W toward the discharge space, reflection of acoustic waves can be suppressed. At the same time, there is an advantage that the flow of the laser gas is less disturbed. The protrusion amount H is preferably 3 mm or less.

  However, if the protrusion amount H is too small, the amount of ultraviolet light irradiated between the main electrodes is reduced. Therefore, the decrease in the amount of light caused by reducing the protrusion amount H can be compensated by adding the preliminary ionization electrode 38. The additional preionization electrode 38 can be placed upstream and downstream of the main electrodes 14 and 15 side.

  FIG. 20 is a diagram in the case where a plurality of preliminary ionization electrodes 38 having a protrusion amount H are arranged on the wall surface of the laser gas flow path.

  In FIG. 20, two preliminary ionization electrodes 38 </ b> C and 38 </ b> D having a protruding amount H are provided upstream and downstream on the wall of the laser gas channel on the main electrode 14 side. Further, preliminary ionization electrodes 38E and 38F indicated by dotted lines are provided on the wall surface of the laser gas flow channel outside the preliminary electrodes 38C and 38D when viewed from the main electrode 14 side. Preionization electrodes 38G, 38H, 38I, and 38J indicated by dotted lines are provided on the wall surface of the laser gas channel on the main electrode 15 side so as to face the preionization electrodes 38E, 38C, 38D, and 38F, respectively.

  According to FIG. 20, it is possible to compensate for the decrease in the amount of light of each preliminary ionization electrode by increasing the number of preliminary ionization electrodes.

  The discharge surface itself of the main electrode also reflects acoustic waves. Part of the acoustic wave repeatedly reflects between the main electrodes and stays in the discharge space. I want to reduce these acoustic waves. Below, the form which reduces the acoustic wave reflected on a discharge surface is described.

  FIGS. 21A and 21B are front views of the main electrodes 14 and 15. In FIG. 21, the direction perpendicular to the paper surface is the electrode longitudinal direction.

  In FIG. 21A, a porous sound absorbing material K is provided on the discharge surfaces 14D and 15D of the main electrodes 14 and 15. If the sound absorbing material K is a conductive member, the impedance between the main electrodes 14 and 15 will not increase. However, the surface of the conductive member is fluorinated and sputtered with a high electric field. For this reason, when the sound-absorbing material K is a conductive member, the sound-absorbing property may be lowered. On the other hand, ceramic-based members have fluorination resistance. From the above, it is preferable to use the ceramic-based sound absorbing material K because the sound absorbing property does not deteriorate. When the ceramic sound absorbing material K is used, an increase in impedance between the main electrodes can be prevented by optimizing the porosity and hole diameter of the sound absorbing material K.

  As a method of providing the sound absorbing material K on the discharge surfaces 14D and 15D of the main electrodes 14 and 15, the sound absorbing material K created in accordance with the shape of the discharge surfaces 14D and 15D is arranged without opening a gap on the discharge surfaces 14D and 15D. The method is preferred. Since the sound absorption rate changes according to the thickness of the sound absorbing material K, the thickness of the sound absorbing material is optimized as appropriate.

  Alternatively, the porous sound absorbing material K may be formed on the discharge surfaces 14D and 15D of the main electrodes 14 and 15 using a thermal spraying method. In general, only a thin film is formed by the thermal spraying method. In order to optimize the thickness of the sound absorbing material K (for example, 1 mm or more), the thermal spraying may be repeated a plurality of times.

  The discharge surfaces 14D and 15D of the main electrodes 14 and 15 and the sound absorbing material K are not necessarily in contact with each other without opening a gap. In short, it is sufficient that the sound absorbing material K is provided in the discharge space so as not to disturb the discharge between the main electrodes 14 and 15. Therefore, as shown in FIG. 21B, the sound absorbing material K may be disposed in the discharge space 37 with a gap between the main electrodes 14 and 15. The sound absorbing material K is supported by a holder (not shown).

  Further, it is not necessary to form the sound absorbing material K on the entire surfaces of the discharge surfaces 14 and 15, and the sound absorbing material K divided into a predetermined size may be provided on the discharge surfaces 14D and 15D.

  The sound absorbing material K is not provided on the discharge surfaces 14D and 15D side of the main electrodes 14 and 15, but may be provided on the back surface side of the discharge surfaces 14D and 15D. Below, the form of the sound absorption material K provided in the back surface side of discharge surface 14D, 15D is demonstrated. In the following description, only the structure on the main electrode 15 side will be described for convenience, but the structure on the main electrode 14 side is the same.

  FIG. 22A is a plan view of the main electrode 15, and FIG. 22B is a YY cross-sectional view of FIG. 22A and 22B, the horizontal direction on the paper is the electrode longitudinal direction.

  The main electrode 15 is formed with a plurality of holes 22 penetrating from the discharge surface 15D to the back surface 15E. A sound absorbing material K is provided on the back surface 15E side of the main electrode 15. A part of the acoustic wave propagating in the Z-axis direction in the discharge space passes through the hole 22 and reaches the sound absorbing material K. Most of the acoustic waves that have reached the sound absorbing material K are absorbed by the sound absorbing material K. Therefore, most of the acoustic wave that has passed through the hole 22 does not return to the discharge space.

  The acoustic wave attenuation rate in the form shown in FIGS. 22A and 22B is defined by the ratio of the total cross-sectional area of the hole 22 to the surface area of the discharge surface 15D of the main electrode 15 (hereinafter referred to as area ratio). . The hole diameter of the hole 22 needs to be such that an acoustic wave can pass through and does not deteriorate the function of the main electrode 15. Considering the above, it is preferable that 0.1 mm ≦ pore diameter ≦ 1 mm. The area ratio may be appropriately determined from the required attenuation rate, but preferably 0.1 ≦ area ratio ≦ 0.9. When the area ratio is large, it is preferable to reduce the hole diameter. The shape of the hole 22 is not particularly limited to a circle, and may be a triangle or a rectangle. The arrangement of the holes 22 may not be a lattice shape as shown in FIG. 24 but may be random. The thickness of the main electrode is preferably 1 mm or more in consideration of deformation due to electric discharge.

  Fig.23 (a) is XX sectional drawing of Fig.22 (a), and is a figure which shows a 1st form. FIG.23 (b) is XX sectional drawing of Fig.24 (a), and is a figure which shows a 2nd form. The sound absorbing material K shown in FIG. 23A is disposed on the back surface 15E side of the main electrode 15. The sound absorbing material K shown in FIG. 23B is stored in a cavity 15F formed on the back surface 15E side of the main electrode 15. The sound absorbing material K and the main electrode 15 may or may not be in contact. The sound absorbing material K need not be provided on the entire back surface of the main electrode 15. The sound absorbing material K only needs to be provided at least corresponding to the position of the hole 22.

  As shown in FIGS. 24 to 26, the main electrode 15 may be provided with a groove instead of being provided with a hole.

  FIG. 24A is a plan view of the main electrode 15, and FIG. 24B is a side view of the main electrode 15. In FIGS. 24A and 24B, the horizontal direction on the paper is the electrode longitudinal direction.

  24, the main electrode 15 includes a plurality of electrodes 15-1, 15-2,..., 15-N arranged in the longitudinal direction. A gap is provided between adjacent electrodes. In this specification, this gap is referred to as a groove 24. A sound absorbing material K is provided on the back surface 15E side of the main electrode 15. A part of the acoustic wave propagating in the Z-axis direction in the discharge space passes through the groove 24 and reaches the sound absorbing material K. Most of the acoustic waves that have reached the sound absorbing material K are absorbed by the sound absorbing material K. Therefore, most of the acoustic waves that have passed through the groove 24 do not return to the discharge space. In consideration of discharge stability and ease of acoustic wave passage, the interval between the grooves 24 is preferably 1 mm or less. The sound absorbing material K may be a conductive member, but a ceramic member is more preferable because it can insulate each electrode. The sound absorbing material K need not be provided on the entire back surface of the main electrode 15. The sound absorbing material K only needs to be provided at least corresponding to the position of the groove 24.

  FIG. 25 is a front view of the main electrode 15. In FIG. 25, the direction perpendicular to the paper surface is the electrode longitudinal direction.

  25, the main electrode 15 is composed of a plurality of electrodes 15-1, 15-2,..., 15-N arranged in the discharge width direction. A gap is provided between adjacent electrodes. In this specification, this gap is referred to as a groove 25. A sound absorbing material K is provided on the back surface 15E side of the main electrode 15. A part of the acoustic wave propagating in the Z-axis direction in the discharge space passes through the groove 25 and reaches the sound absorbing material K. Most of the acoustic waves that have reached the sound absorbing material K are absorbed by the sound absorbing material K. Therefore, most of the acoustic waves that have passed through the groove 25 do not return to the discharge space. In consideration of discharge stability and ease of acoustic wave passage, the interval between the grooves 25 is preferably 0.5 mm or less. The sound absorbing material K may be a conductive member, but a ceramic member is more preferable because it can insulate each electrode. The sound absorbing material K need not be provided on the entire back surface of the main electrode 15. The sound absorbing material K only needs to be provided at least corresponding to the position of the groove 25.

  FIG. 26A is a plan view of the main electrode 15, and FIG. 26B is a side view of the main electrode 15. In FIGS. 26A and 26B, the horizontal direction on the paper is the electrode longitudinal direction.

  The grooves 25 shown in FIGS. 25 (a) and 25 (b) are merely gaps, but the sound absorbing material K is provided in the grooves 26 shown in FIGS. 26 (a) and 26 (b). Although not shown, the sound absorbing material K may not be provided on the back surface 15E side of the main electrode 15, and the sound absorbing material K may be provided only in the groove 25.

  In the present embodiment, the mode in which the sound absorbing material K is provided on the discharge surfaces 14D and 15D side or the back surface 15E side of the main electrodes 14 and 15 has been described. However, the sound absorbing material K is not necessarily provided on both the main electrodes 14 and 15. The sound absorbing material K may be provided only on one of the main electrodes 14 and 15.

The pulse oscillation type discharge excitation laser apparatus of the present invention is applicable not only to semiconductor manufacturing but also to all fields as a laser source for fine processing with high output.

It is a figure which shows the example of 1 structure of a gas laser apparatus. It is a figure which shows the relationship between the oscillation frequency at the time of receiving the influence of an acoustic wave, and a spectrum line width. It is a schematic diagram for demonstrating a mode that an acoustic wave propagates. It is a figure which shows the structure of the gas laser apparatus which concerns on embodiment of this invention. It is a figure which shows sectional drawing of the main electrode vicinity in a laser chamber. 4 is a schematic diagram for explaining an inclination angle of a smooth laser gas flow path W. FIG. It is a schematic diagram in which a laser gas channel wall surface having a large inclination angle is formed. It is a cross-sectional schematic diagram of the electrode vicinity for demonstrating the laser gas flow path W of 2 steps | paragraphs of inclination angles. It is a block diagram of two types of laser gas flow paths W for carrying out simulation comparison of the sound pressure between main electrodes. It is a comparison figure of the result of having simulated the effective value of the sound pressure between main electrodes. It is a figure for demonstrating the relationship of the two inclination angles in the laser gas flow path which has a 2 step | paragraph inclination. It is a figure for demonstrating the form of an inclined surface and a wall surface. It is a figure explaining the case where an inclined surface is a curved surface shape. It is a figure which shows the case where the side surface of the main electrode 15 is a taper-shaped shape. It is a schematic diagram of the vicinity of the main electrode when the most efficient arrangement of the sound absorbing material is used to attenuate the acoustic energy of the acoustic wave component in the Z-axis direction. It is a figure for demonstrating the case where the sound-absorbing material is arrange | positioned in the main electrode vicinity. It is a schematic diagram of the cross-sectional structure of a preionization electrode. It is a schematic diagram which shows the case where a sound-absorbing material is provided in the laser gas flow path wall surface other than the main electrode and the preionization electrode. It is a schematic diagram which shows sound-absorbing material arrangement | positioning by simulation. It is a figure in case a plurality of preliminary ionization electrodes are arranged on the wall surface of the laser gas channel. It is a figure which shows the case where a sound-absorbing material is provided in the upper part of the discharge surface. It is a figure which shows the case where a sound-absorbing material is provided in the back surface of the main electrode. It is a figure explaining embodiment by which a sound-absorbing material is provided in the back surface of a main electrode. It is a figure for demonstrating the sound absorption material arrangement | positioning in the divided | segmented main electrode. It is a figure for demonstrating the sound-absorbing material arrangement | positioning in the other divided | segmented main electrode. It is a figure explaining the case where the sound-absorbing material is provided in the groove | channel of the divided | segmented main electrode.

Explanation of symbols

K sound absorbing material H protrusion amount W laser gas flow path 12 laser chamber 14 anode electrode 14D discharge surface 15 cathode electrode 15D discharge surface 37 discharge space 38 preliminary ionization electrode 41 acoustic wave

Claims (4)

Pulse oscillation type discharge excitation in which a high voltage is applied between a main electrode composed of a pair of an anode electrode and a cathode electrode arranged opposite each other to perform a pulsed main discharge and a pulse oscillation with a maximum oscillation frequency of 4 kHz or more. In the laser device,
A sound-absorbing material provided with no gap between the discharge surface of at least one of the anode electrode and the cathode electrode or provided with a gap between the discharge surface in the discharge space A pulse oscillation type discharge excitation laser device comprising: Pulse oscillation type discharge excitation in which a high voltage is applied between a main electrode composed of a pair of an anode electrode and a cathode electrode arranged opposite each other to perform a pulsed main discharge and a pulse oscillation with a maximum oscillation frequency of 4 kHz or more. In the laser device,
At least one of the anode electrode and the cathode electrode has a hole or groove penetrating from the discharge surface to the back surface side, and a sound absorbing material is provided on the back surface side corresponding to the position of the hole or groove. A pulse oscillation type discharge excitation laser device characterized by being provided. Pulse oscillation type discharge excitation in which a high voltage is applied between a main electrode composed of a pair of an anode electrode and a cathode electrode arranged opposite each other to perform a pulsed main discharge and a pulse oscillation with a maximum oscillation frequency of 4 kHz or more. In the laser device,
A pulse characterized in that a hole or groove penetrating from the discharge surface to the back surface side of at least one of the anode electrode and the cathode electrode is formed, and a sound absorbing material is embedded in the hole or groove. Oscillation type discharge excitation laser device. 4. The pulse oscillation type discharge excitation laser device according to claim 1, wherein the sound absorbing material is a ceramic material.

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