JP4818763B2 - Preionization electrode for gas laser - Google Patents

Description

  The present invention relates to a preionization electrode for a gas laser provided in parallel with the longitudinal direction of a pair of main discharge electrodes for exciting a laser gas, and more particularly to the structure of the preionization electrode.

  As semiconductor integrated circuits are miniaturized and highly integrated, improvement in resolving power is demanded in semiconductor exposure apparatuses. For this reason, the wavelength of light emitted from the exposure light source is being shortened. As a light source for exposure, a gas laser device is used instead of a conventional mercury lamp. At present, a KrF excimer laser that emits ultraviolet light having a wavelength of 248 nm is used as a gas laser device for exposure. Further, as a next-generation light source for semiconductor exposure, gas laser devices that emit ultraviolet rays, such as an ArF excimer laser device having a wavelength of 193 nm and a fluorine (F2) laser device having a wavelength of 157 nm, are promising.

  The gas laser device includes a laser chamber in which windows are provided on both wall surfaces, and resonators disposed on both sides of the laser chamber on an optical axis outside the laser chamber. Various laser gases are sealed in the laser chamber at a pressure of several hundred kPa. Light is emitted when the laser gas is excited in this laser chamber and transitions to a stable state. Light is output from one window to the outside of the laser chamber, reflected by one resonator, and input from one window to the inside of the laser chamber. Then, the light is output from the other window to the outside of the laser chamber, reflected by the other resonator, and input from the other window to the inside of the laser chamber. In this way, light reciprocates between the resonators and is amplified in the laser chamber. Laser light is output outside the resonator.

  Discharge is used as a laser gas excitation method. As shown in FIG. 5, a pair of main discharge electrodes 2 and 3 are provided in the laser chamber 1 to excite laser gas by discharge. The pair of main discharge electrodes 2 and 3 are arranged so that their longitudinal directions are parallel to each other and their discharge surfaces are spaced apart from each other by a predetermined distance. When a high voltage is applied between the pair of main discharge electrodes 2 and 3 and the voltage reaches a certain value (breakdown voltage), the laser gas between the main discharge electrodes 2 and 3 breaks down. Then, a main discharge is generated between the main discharge electrodes 2 and 3, and the laser gas is excited.

In the vicinity of the main discharge electrodes 2 and 3, a preionization electrode 10 is arranged in parallel with the longitudinal direction of the main discharge electrodes 2 and 3. The preliminary ionization electrode 10 includes a pipe-shaped dielectric 11, an inner electrode 12 along the longitudinal direction of the dielectric 11 on the inner peripheral surface side of the dielectric 11, and a longitudinal direction of the dielectric 11 on the outer peripheral surface side of the dielectric 11. And an outer electrode 13 extending along the line. When a high voltage is applied to the inner electrode 12, corona discharge is generated on the outer peripheral surface of the dielectric 11 starting from the contact portion between the dielectric 11 and the outer electrode 13. This corona discharge preliminarily ionizes the laser gas between the main discharge electrodes 2 and 3 and the main discharge is likely to occur.

  The gas laser device outputs pulsed laser light by repeating such preliminary ionization and main discharge. Currently, the repetition frequency of laser light used for semiconductor exposure is shifted from about 2 kHz to about 4 kHz.

Here, the shape of the main discharge electrodes 2 and 3, the structure of the preionization electrode 10, and the arrangement of both will be further described.
FIG. 6 shows a main discharge electrode and a conventional preionization electrode. FIG. 6 shows the shape of the cross section passing through the central axis parallel to the longitudinal direction and the discharge direction with respect to the main discharge electrode, and the structure of the cross section passing through the central axis parallel to the longitudinal direction with respect to the preionization electrode. It is. FIG. 6 shows the relative positions in the longitudinal direction of the main discharge electrode and the preionization electrode, that is, the horizontal direction in the drawing, and does not show the relative positions in the vertical direction and the front-back direction in the drawing.

  As shown in FIG. 6, the main discharge electrodes 2 and 3 have flat portions 2f and 3f whose discharge surfaces are flat with respect to the longitudinal direction, and thicknesses on both sides of the flat portions 2f and 3f toward the longitudinal ends. The slopes 2s and 3s are inclined so that the discharge surface is slanted. The reason why the inclined portions 2s and 3s are formed is to create so-called discharge escape regions at both ends in the longitudinal direction of the main discharge space (between the main discharge electrodes 2 and 3). By creating this discharge escape region, the electric field intensity gradually attenuates as it advances toward the main discharge space end, and the main discharge also attenuates gradually as it advances toward the main discharge space end. As a result, a stable discharge can be produced without causing an abnormal discharge such as an arc or streamer.

As shown in FIG. 6, the outer electrode 13 of the preliminary ionization electrode 10 is the same as the length of the main discharge electrodes 2 and 3 or longer than the length of the main discharge electrodes 2 and 3. Further, most of the inner electrode 12 is occupied by the large diameter portion having the diameter φ1, but the diameter is reduced near the end portion, and the vicinity of the end portion becomes a small diameter portion having the diameter φ2. A pipe-like insulating ceramic 14 is embedded on both ends of the dielectric 11 on the outer peripheral side of the small diameter portion of the inner electrode 12 so as to be coaxial with the dielectric 11 and the inner electrode 12. The insulating ceramic 14 ensures insulation between the inner electrode 12 and the inner wall surface of the laser chamber.

  The preionization region is determined according to the arrangement of the outer electrode 13. That is, preliminary ionization occurs in a portion where the outer electrode 13 exists, and no preliminary ionization occurs in a portion where the outer electrode 13 does not exist. In general, since the intensity of preionization is constant over the entire main discharge space including the discharge escape region, the length of the outer electrode 13 is equal to the length of the main electrodes 2 and 3 as shown in FIG. Have been long.

  By the way, in recent years, in order to increase throughput and reduce variations in exposure amount, further increase in repetition frequency and higher output of laser light are desired. Currently, the realization of a repetition frequency of about 6 kHz or more is being studied. In order to increase the output of laser light, a double chamber type laser apparatus having two chambers has been developed. The double chamber laser device includes an oscillation stage that outputs laser light and an amplification stage that further amplifies and outputs laser light output from the oscillation stage. Each of the oscillation stage and the amplification stage includes a laser chamber (oscillation chamber, amplification chamber) having a main discharge electrode and a preionization electrode.

  There are two known types of double-chamber laser devices, the MOPO method and the MOPA method, which have different amplification means in the amplification stage. MOPO is an abbreviation for Master Oscillator and Power Oscillator, and is also called an injection lock system. In this system, a resonator is provided with an amplification chamber interposed therebetween, and laser light passes through the amplification chamber a plurality of times and is amplified. MOPA is an abbreviation for Master Oscillator and Power Amplifier. In this system, a resonator is not provided with an amplification chamber interposed therebetween, and laser light is amplified by passing through the amplification chamber once or twice.

  However, when the repetition frequency was increased to about 6 kHz in the double chamber laser device, it was found that abnormal discharge occurred in the amplification stage chamber. Since the deterioration of the discharge state causes the deterioration of the quality of the laser beam and adversely affects the exposure of the semiconductor, it is necessary to prevent abnormal discharge.

  The inventors have found that abnormal discharge occurs when non-uniform discharges such as arcs and streamers generated at the ends of the main discharge space grow as the repetition frequency increases and the stability of the main discharge is impaired. I thought that. According to the experiments by the present inventors, it was found that the discharge stability deteriorates in the vicinity of the end portion of the main discharge electrode, particularly in the high repetition laser oscillation operation in which the pulse oscillation repetition number exceeds 4 KHz.

Regarding abnormal discharge, the following can be considered regarding preionization. Although it is not intended to generate the main discharge in the discharge escape region, the conventional structure generates pre-ionization with the same intensity in the entire main discharge space including the discharge escape region. The main discharge of considerable intensity also occurs in the escape area. Further, the main discharge intensity in the discharge escape region is weaker than the original main discharge intensity. A discharge generated in such a portion having a low electric field strength is more unstable than a discharge generated in a portion having a high electric field strength. Therefore, during a high repetition operation such as 6 KHz, it becomes easy to shift to non-uniform discharge such as an arc or streamer. Therefore, the preionization that occurs in the discharge escape region is a cause of impairing the stability of the discharge during a high repetitive operation exceeding 6 KHz.

  Therefore, the present inventor needs to optimize the end treatment for the high repetition operation of 6 KHz or more, such as the discharge escape region near the electrode end, and it is most effective to optimize the preionization region I thought.

  The present invention has been made in view of such circumstances, and abnormal main discharge is generated even in a high-frequency / high-power laser device by changing the intensity distribution of preionization near both longitudinal ends of the main discharge space. Therefore, the object is to enable stable semiconductor exposure.

The first invention is
Provided in a chamber of a gas laser device having a pulse oscillation repetition rate exceeding 4 KHz,
A pipe-shaped dielectric (11), an inner electrode (12) along the longitudinal direction of the dielectric (11) on the inner peripheral surface of the dielectric (11), and an outer peripheral surface of the dielectric (11) And an outer electrode (13) along the longitudinal direction of the dielectric (11),
A flat portion (2f, 3f) having a flat discharge surface with respect to the longitudinal direction, and an inclination at which the discharge surface is inclined so as to be thinner at both ends of the flat portion (2f, 3f) in the longitudinal direction. In the preliminary ionization electrode for gas laser provided in parallel with the longitudinal direction of the pair of main discharge electrodes (2, 3) consisting of a portion (2s, 3s),
The length of the flat portion (2f, 3f) in the longitudinal direction is L1,
The distance between the opposing flat portions (2f, 3f) of the pair of main discharge electrodes (2, 3) is D1,
Between the position on one side in the longitudinal direction and the position on the other side where the distance between the inclined portions (2s, 3s) facing the pair of main discharge electrodes (2, 3) is any value of 1.1D1 to 1.2D1 When the interval is D2,
The length of the outer electrode (13) in the longitudinal direction is not less than L1 and not more than D2.

The second invention is the first invention,
The shape of the cross section orthogonal to the longitudinal direction is substantially the same as the shape of the outer electrode (13), which is in contact with the longitudinal end of the outer electrode (13) and on the outer peripheral surface of the dielectric (11). It has a dielectric (15, 16) for laser gas rectification that abuts.

Conventionally, the length of the outer electrode of the preionized electrodes is equal to or longer than the length of the main discharge electrode, but the length of the outer electrode 13 of the first invention is shorter than the length of the main discharge electrodes 2 and 3. Specifically, the length of the flat portions 2f and 3f of the main discharge electrodes 2 and 3 in the longitudinal direction is L1, the interval between the flat portions 2f and 3f facing each other is D1, and the inclined portions 2s and 3s facing each other are arranged. When the distance between the position on the one side in the longitudinal direction and the position on the other side where the distance is any value between 1.1D1 and 1.2D1 is D2, the length of the outer electrode 13 is not less than L1 and not more than D2. is there.

  In the second invention, the dielectrics 15 and 16 for laser gas rectification are provided in the portion where the conventional outer electrode is present. Although the outer electrode also forms a laser gas flow path, the laser gas flow path is partially lost by shortening the outer electrode. The dielectrics 15 and 16 for laser gas rectification make up for the missing flow path.

The third invention is
Provided in a chamber of a gas laser device having a pulse oscillation repetition rate exceeding 4 KHz,
A pipe-shaped dielectric (11), an inner electrode (12) along the longitudinal direction of the dielectric (11) on the inner peripheral surface of the dielectric (11), and an outer peripheral surface of the dielectric (11) And an outer electrode (13) along the longitudinal direction of the dielectric (11),
A flat portion (2f, 3f) having a flat discharge surface with respect to the longitudinal direction, and an inclination at which the discharge surface is inclined so as to be thinner at both ends of the flat portion (2f, 3f) in the longitudinal direction. In the preliminary ionization electrode for gas laser provided in parallel with the longitudinal direction of the pair of main discharge electrodes (2, 3) consisting of a portion (2s, 3s),
The inner electrode (12) has a large diameter portion and small diameter portions located on both sides of the large diameter portion,
The length of the flat portion (2f, 3f) in the longitudinal direction is L1,
The distance between the opposing flat portions (2f, 3f) of the pair of main discharge electrodes (2, 3) is D1,
Between the position on one side in the longitudinal direction and the position on the other side where the distance between the inclined portions (2s, 3s) facing the pair of main discharge electrodes (2, 3) is any value of 1.1D1 to 1.2D1 When the interval is D2,
The length in the longitudinal direction of the large diameter portion of the inner electrode (12) is not less than L1 and not more than D2.

Conventionally, the length of the large-diameter portion of the inner electrode of the preionized electrodes is equal to or longer than the length of the main discharge electrode. However, the length of the large-diameter portion of the inner electrode 12 of the third invention is the main discharge electrode 2. Shorter than 3. Specifically, the length of the flat portions 2f and 3f of the main discharge electrodes 2 and 3 in the longitudinal direction is L1, the interval between the flat portions 2f and 3f facing each other is D1, and the inclined portions 2s and 3s facing each other are arranged. When the distance between the position on the one side in the longitudinal direction and the position on the other side where the distance is any value between 1.1D1 and 1.2D1 is D2, the length of the large diameter portion of the inner electrode 12 is L1 or more. , D2 or less.

  According to the first invention, since the outer electrode is shorter than the conventional one, the main discharge at the longitudinal end of the main discharge space is also greatly reduced as the preionization intensity near both ends of the main discharge electrode is greatly reduced. To do. Therefore, even if a high repetition operation with a pulse oscillation repetition rate of 6 KHz or more is performed, abnormal discharge can be suppressed and discharge stability can be improved, so that semiconductor exposure can be performed stably.

  According to the third invention, since the large-diameter portion of the inner electrode is shorter than before, the main discharge at the longitudinal end portion of the main discharge space is greatly reduced as the preionization intensity in the vicinity of both ends of the main discharge electrode is greatly reduced. Is also significantly reduced. Therefore, even if a high repetition operation with a pulse oscillation repetition rate of 6 KHz or more is performed, abnormal discharge can be suppressed and discharge stability can be improved, so that semiconductor exposure can be performed stably.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following embodiments, a main discharge electrode and a preionization electrode provided in an amplification stage of a double chamber laser apparatus that oscillates at a high repetition rate of about 6 kHz or more are assumed. The “longitudinal direction” used in the description of each embodiment refers to the longitudinal direction of the main discharge electrode and the preionization electrode.

  The preionization intensity between the main discharge electrodes is affected by the form of the outer electrode among the preionization electrodes. The first embodiment relates to the form of the outer electrode.

  FIG. 1 shows a main discharge electrode and a preionization electrode according to the first embodiment. FIG. 1 shows a cross-sectional shape that passes through the central axis parallel to the longitudinal direction and the discharge direction for the main discharge electrode, and a cross-sectional structure that passes through the central axis parallel to the longitudinal direction for the preionization electrode. It is. FIG. 1 shows the relative positions in the longitudinal direction of the main discharge electrode and the preionization electrode, that is, the horizontal direction in the drawing, and does not show the relative positions in the vertical direction and the front-back direction in the drawing.

  Each component of the main discharge electrode according to the first embodiment shown in FIG. 1 is the same as each component of the conventional main discharge electrode shown in FIG. For this reason, each component of the main discharge electrode shown in FIG. 1 is assigned the same reference numeral as each component of the main discharge electrode shown in FIG. Further, the constituent elements of the preionization electrode according to the first embodiment shown in FIG. 1 and the constituent elements of the conventional preionization electrode shown in FIG. 6 are the same except for some elements such as the length. For this reason, each component of the preionization electrode shown in FIG. 1 is assigned the same reference numeral as each component of the preionization electrode shown in FIG. That is, the preliminary ionization electrode 10 includes a pipe-shaped dielectric 11, an inner electrode 12 along the longitudinal direction of the dielectric 11 on the inner peripheral surface side of the dielectric 11, and the dielectric 11 on the outer peripheral surface side of the dielectric 11. And an outer electrode 13 along the longitudinal direction. Although not shown in the figure, it has a pipe-like insulating ceramic embedded in both ends of the dielectric 11 so as to be coaxial with the dielectric 11 and the inner electrode 12.

Here, the length of each part used in the description of the present embodiment and the reference plane are defined.
L1: Length in the longitudinal direction of the flat portions 2f and 3f.
D1: A distance between the flat portions 2f and 3f facing each other of the pair of main discharge electrodes 2 and 3.
D2: A distance between a position on one side in the longitudinal direction and a position on the other side where the distance between the opposed inclined portions 2s, 3s of the pair of main discharge electrodes 2, 3 is any value of 1.1D1 to 1.2D1 .
P1: An imaginary plane that is orthogonal to the longitudinal direction of the main discharge electrodes 2 and 3 and on which one end portions 2fa and 3fa of the flat portions 2f and 3f of the main discharge electrodes 2 and 3 are located.
P2: An imaginary plane orthogonal to the longitudinal direction of the main discharge electrodes 2 and 3 and where the other end portions 2fb and 3fb of the flat portions 2f and 3f of the main discharge electrodes 2 and 3 are located.
P3: An imaginary plane including a position on one side in the longitudinal direction in which the interval between the inclined portions 2s, 3s facing each other of the pair of main discharge electrodes 2, 3 is any value of 1.1D1 to 1.2D1 .
P4: An imaginary plane including a position on the other side in the longitudinal direction in which the interval between the inclined portions 2s, 3s facing each other of the pair of main discharge electrodes 2, 3 is any value of 1.1D1 to 1.2D1 .

As shown in FIG. 1, one end 13a of the outer electrode 13 is located between the plane P1 and the plane P3, and the other end 13b of the outer electrode 13 is located between the plane P2 and the plane P4. The interval between the plane P1 and the plane P2 is equal to the length L1 of the flat portions 2f and 3f of the main discharge electrodes 2 and 3, and the interval between the plane P2 and the plane P4 is the inclined portion 2s facing the main discharge electrodes 2 and 3, This is the distance D2 itself between the position on the one side in the longitudinal direction and the position on the other side in which the distance of 3s takes any value between 1.1D1 and 1.2D1 . That is, the length of the outer electrode 13 in the longitudinal direction is not less than L1 and not more than D2.

  In addition, the preionization electrode 10 of the present embodiment has a cross-sectional shape orthogonal to the longitudinal direction substantially the same as the shape of the outer electrode 13, is in contact with one end portion 13 a of the outer electrode 13, and is an outer peripheral surface of the dielectric 11. And a laser gas rectifying dielectric 16 in contact with the other end 13 a of the outer electrode 13 and in contact with the outer peripheral surface of the dielectric 11.

The dielectrics 15 and 16 will be described.
As shown in FIG. 1, the length of the outer electrode 13 is shorter than the length of the main discharge electrodes 2 and 3. In such a configuration, the laser gas flow is disturbed near the end portion between the main discharge electrodes 2 and 3, and the uniformity of the laser gas flow is reduced. In a laser using a gas discharge as an excitation source, it is necessary to replace the laser gas in the main discharge space immediately after the discharge in order to prevent the gas used for the discharge from affecting the next discharge. A high-speed laser gas flow is generated between them. As can be seen from FIG. 5, the outer electrode 13 has a role of causing preionization, and a laser gas flow path is formed between the pipe-shaped dielectric 11 and the main discharge electrode 3, so that the laser gas flow is smooth. There is also a role to do. If the outer electrode 13 is shortened, a part of the laser gas flow path is lost between the main discharge electrode 3 and the dielectric 11, and the laser gas is disturbed and the laser gas does not flow smoothly.

  Since the discharge tends to become unstable particularly at the ends of the main discharge electrodes 2 and 3, it is desirable to avoid a decrease in gas flow rate near the ends of the main discharge electrodes 2 and 3. Therefore, in the present embodiment, the outer electrode 13 is shortened, and the dielectrics 15 and 16 whose cross-sectional shape orthogonal to the longitudinal direction coincides with the cross-sectional shape of the outer electrode 13 are arranged on both sides in the longitudinal direction of the outer electrode 13. . The dielectrics 15 and 16 are preferably composed of a ceramic material such as alumina ceramics in order to avoid contamination of the laser gas.

  If attention is paid only to the fact that the preionization intensity in the vicinity of both ends of the main discharge electrodes 2 and 3 is significantly reduced, as shown in FIG. 2, the one end 13a of the outer electrode 13 is flat with the plane P1. It is only necessary to be positioned between P3 and the other end 13b of the outer electrode 13 is positioned between the plane P2 and the plane P4, and no dielectric is provided on both sides of the outer electrode 13. Also good.

  According to the present embodiment, since the outer electrode is shorter than the conventional one, the main discharge at the longitudinal end of the main discharge space is also greatly reduced as the preionization intensity near both ends of the main discharge electrode is greatly reduced. To do. Therefore, even if a high repetition operation with a pulse oscillation repetition rate of 6 KHz or more is performed, abnormal discharge can be suppressed and discharge stability can be improved, so that semiconductor exposure can be performed stably.

  The preionization intensity between the main discharge electrodes is affected by the form of the inner electrode among the preionization electrodes. The second embodiment relates to the form of the inner electrode.

  FIG. 3 shows the main discharge electrode and the preionization electrode according to the second embodiment. FIG. 3 shows the shape of a cross section passing through the central axis parallel to the longitudinal direction and the discharge direction with respect to the main discharge electrode, and the structure of the cross section passing through the central axis parallel to the longitudinal direction with respect to the preionization electrode. It is. FIG. 3 shows the relative positions in the longitudinal direction of the main discharge electrode and the preliminary ionization electrode, that is, the horizontal direction in the drawing, and does not show the relative positions in the vertical direction and the front-back direction in the drawing.

  Each component of the main discharge electrode according to the second embodiment shown in FIG. 3 is the same as each component of the conventional main discharge electrode shown in FIG. For this reason, each component of the main discharge electrode shown in FIG. 3 is assigned the same reference numeral as each component of the main discharge electrode shown in FIG. Moreover, each component of the preionization electrode according to the second embodiment shown in FIG. 3 and each component of the conventional preionization electrode shown in FIG. 6 are the same except for some elements such as length. For this reason, each component of the preionization electrode shown in FIG. 3 is given the same reference numeral as each component of the preionization electrode shown in FIG. That is, the preliminary ionization electrode 10 includes a pipe-shaped dielectric 11, an inner electrode 12 along the longitudinal direction of the dielectric 11 on the inner peripheral surface side of the dielectric 11, and the dielectric 11 on the outer peripheral surface side of the dielectric 11. It has the outer electrode 13 along a longitudinal direction, and the pipe-shaped insulation ceramic 14 embed | buried under the both ends of the dielectric material 11 so that it may become coaxial with the dielectric material 11 and the inner electrode 12. FIG.

The length of each part and the reference position used in the description of this embodiment are common to those of the first embodiment, but are defined here again.
L1: Length in the longitudinal direction of the flat portions 2f and 3f.
D1: A distance between the flat portions 2f and 3f facing each other of the pair of main discharge electrodes 2 and 3.
D2: A distance between a position on one side in the longitudinal direction and a position on the other side where the distance between the opposed inclined portions 2s, 3s of the pair of main discharge electrodes 2, 3 is any value of 1.1D1 to 1.2D1 .
φ1: The diameter of the large diameter portion of the inner electrode 12.
φ2: Diameter of the small diameter portion of the inner electrode 12.
P1: An imaginary plane that is orthogonal to the longitudinal direction of the main discharge electrodes 2 and 3 and on which one end portions 2fa and 3fa of the flat portions 2f and 3f of the main discharge electrodes 2 and 3 are located.
P2: An imaginary plane orthogonal to the longitudinal direction of the main discharge electrodes 2 and 3 and where the other end portions 2fb and 3fb of the flat portions 2f and 3f of the main discharge electrodes 2 and 3 are located.
P3: An imaginary plane including a position on one side in the longitudinal direction in which the interval between the inclined portions 2s, 3s facing each other of the pair of main discharge electrodes 2, 3 is any value of 1.1D1 to 1.2D1 .
P4: An imaginary plane including a position on the other side in the longitudinal direction in which the interval between the inclined portions 2s, 3s facing each other of the pair of main discharge electrodes 2, 3 is any value of 1.1D1 to 1.2D1 .

As shown in FIG. 3, one end portion 12a of the large-diameter portion of the inner electrode 12 is located between the plane P1 and the plane P3, and the other end portion 12b of the large-diameter portion of the inner electrode 12 is formed between the plane P2 and the plane P4. Located between. The interval between the plane P1 and the plane P2 is equal to the length L1 of the flat portions 2f and 3f of the main discharge electrodes 2 and 3, and the interval between the plane P2 and the plane P4 is the inclined portion 2s facing the main discharge electrodes 2 and 3, This is the distance D2 itself between the position on the one side in the longitudinal direction and the position on the other side in which the distance of 3s takes any value between 1.1D1 and 1.2D1 . That is, the length in the longitudinal direction of the large diameter portion of the inner electrode 12 is not less than L1 and not more than D2.

  According to this embodiment, since the large-diameter portion of the inner electrode is shorter than in the prior art, the main discharge at the longitudinal ends of the main discharge space is greatly reduced as the preionization intensity near both ends of the main discharge electrode is greatly reduced. Is also significantly reduced. Therefore, even if a high repetition operation with a pulse oscillation repetition rate of 6 KHz or more is performed, abnormal discharge can be suppressed and discharge stability can be improved, so that semiconductor exposure can be performed stably.

  The third embodiment relates to the form of the outer electrode and the inner electrode.

  FIG. 4 shows the main discharge electrode and the preionization electrode according to the third embodiment. FIG. 4 shows the shape of a cross section passing through the central axis parallel to the longitudinal direction and the discharge direction with respect to the main discharge electrode, and the structure of the cross section passing through the central axis parallel to the longitudinal direction with respect to the preionization electrode. It is. FIG. 4 shows the relative positions in the longitudinal direction of the main discharge electrode and the preionization electrode, that is, the horizontal direction in the drawing, and does not show the relative positions in the vertical direction and the front-back direction in the drawing.

  This embodiment includes the outer electrode 13 of the first embodiment shown in FIGS. 1 and 2, the inner electrode 12 of the second embodiment shown in FIG. 3, and the dielectrics 15 and 16 shown in FIG. It is a combination. This embodiment can reduce the preionization intensity in the vicinity of both ends of the main discharge electrode, compared to the first and second embodiments.

  According to this embodiment, since the large-diameter portion of the inner electrode is shorter than in the prior art, the main discharge at the longitudinal ends of the main discharge space is greatly reduced as the preionization intensity near both ends of the main discharge electrode is greatly reduced. Is also significantly reduced. Therefore, even if a high repetition operation with a pulse oscillation repetition rate of 6 KHz or more is performed, abnormal discharge can be suppressed and discharge stability can be improved, so that semiconductor exposure can be performed stably.

In each embodiment, it is assumed that the preliminary ionization electrode 10 is applied to the amplification stage of the double chamber type laser device that oscillates at a high repetition rate of about 6 kHz or more. However, the preliminary ionization electrode 10 is used as the oscillation stage. The present invention may be applied to a single chamber type laser apparatus. Further, the preionization electrode 10 may be applied to a laser device that oscillates at about 6 kHz or less. When the pulse oscillation repetition number is 4 KHz or more, an effect of suppressing abnormal discharge can be obtained.

FIG. 1 is a diagram showing a main discharge electrode and a preionization electrode according to the first embodiment. FIG. 2 is a diagram showing another embodiment of the main discharge electrode and the preionization electrode according to the first embodiment. FIG. 3 shows the main discharge electrode and the preionization electrode according to the second embodiment. FIG. 4 is a view showing the main discharge electrode and the preionization electrode according to the third embodiment. FIG. 5 is a view showing the structure in the laser chamber. FIG. 6 is a diagram showing a main discharge electrode and a preionization electrode according to a conventional embodiment.

Explanation of symbols

2, 3 ... Main discharge electrode 2f, 3f ... Flat part 2s, 3s ... Inclined part 10 ... Preionization electrode 11 ... Dielectric 12 ... Inner electrode 13 ... Outer electrode 15, 16 ... Dielectric

Claims (1)

In a gas laser device with a pulse oscillation repetition rate exceeding 4 kHz,
A pair of main discharge electrodes (2, 3) provided in the chamber of the gas laser device, the flat portions (2f, 3f) having a flat discharge surface in the longitudinal direction, and the flat portions (2f, 3f) ) And a pair of main discharge electrodes (2, 3) comprising inclined portions (2s, 3s) in which the discharge surface is inclined so that the thickness is thinner toward the end in the longitudinal direction;
A gas laser preionization electrode (10) provided in parallel with the longitudinal direction of the pair of main discharge electrodes (2, 3),
The gas laser preionization electrode (10) is:
A pipe-shaped dielectric (11), an inner electrode (12) along the longitudinal direction of the dielectric (11) on the inner peripheral surface of the dielectric (11), and an outer peripheral surface of the dielectric (11) And having an outer electrode (13) along the longitudinal direction of the dielectric (11),
The inner electrode (12) has a large diameter portion and small diameter portions located on both sides of the large diameter portion,
The length in the longitudinal direction of the flat portions (2f, 3f) of the pair of main discharge electrodes (2, 3) is L1,
The distance between the opposing flat portions (2f, 3f) of the pair of main discharge electrodes (2, 3) is D1,
The distance between the inclined portions (2s, 3s) facing the pair of main discharge electrodes (2, 3) is any value between 1.1D1 and 1.2D1, and the position on one side in the longitudinal direction and the other side When the distance from the position is D2,
The length in the longitudinal direction of the large diameter portion of the inner electrode (12) is not less than L1 and not more than D2.
The length of the longitudinal direction of the inner electrode (12) is longer than the length of the pair of main discharge electrodes (2, 3) in the longitudinal direction.

Images