JP6111145B2 - Plasma light source - Google Patents

Description

  The present invention relates to a plasma light source that generates extreme ultraviolet light.

  In order to further miniaturize semiconductor circuits, extreme ultraviolet light has attracted attention as the next generation irradiation light in photolithography. As a method for generating extreme ultraviolet light, a method using high energy density plasma is known. In this method, high-temperature plasma is generated in a plasma light source, and extreme ultraviolet light is emitted as the radiation light. The high-temperature plasma is mainly generated by a laser generated plasma (LPP) method using pulsed laser irradiation or a discharge plasma (DPP) method using pulse discharge. Patent Document 1 shows an extreme ultraviolet light source based on the LPP method. In any of the above methods, the generated light is pulsed light.

  In the DPP method, an initial discharge for generating plasma is generated using a discharge electrode, and electric energy for growing (heating) the plasma is input after the plasma is generated. Since this discharge electrode is necessarily close to the plasma, it is easily damaged by the radiant heat of the plasma.

JP 2010-287479 A

  In photolithography, control of the exposure time is extremely important. Therefore, it is necessary not only to secure sufficient intensity and luminance, but also to obtain these stably. That is, in the DPP type plasma light source, it is important to surely discharge each time and continuously generate pulsed plasma. Moreover, in order to obtain extreme ultraviolet light, it is essential to increase the temperature of the plasma.

  By the way, when generating plasma that emits extreme ultraviolet light, it is conceivable to use a low melting point metal such as Li as the medium (hereinafter referred to as plasma medium). Li emits extreme ultraviolet light having a wavelength of about 13.5 nm. In order to supply the low melting point metal to the plasma, it is necessary to generate neutral gas or ions of the low melting point metal. One method is ablation using laser light (hereinafter referred to as laser ablation). In laser ablation, laser light is irradiated to an irradiation region formed of a material containing a plasma medium. Since the energy of the laser beam is very large, the plasma medium evaporates and is released into the space as neutral gas or ions.

  In the laser ablation irradiation region, the low melting point metal is held in a liquid state. Specifically, an uneven surface or a porous surface as a plasma medium holding part (hereinafter simply referred to as a medium holding part) is provided in the irradiation region, and the low melting point metal is used by utilizing the surface tension of the liquid low melting point metal. Hold. On the other hand, the energy given to the irradiation region is very large. Therefore, in the irradiation region immediately after ablation, the amount of the low melting point metal temporarily decreases, and the original state (amount) is restored by the subsequent flow of the low melting point metal. However, since the laser irradiation is repeated at an early cycle of about 1 kHz, there is a possibility that the laser beam is irradiated again before the filling is completed. In this case, the medium holding unit is irradiated with high-energy laser light, and the irradiated medium holding unit is damaged by the energy of the laser beam. When the medium holding portion is damaged, the subsequent holding of the low melting point metal becomes insufficient, and the supply of the plasma medium to the plasma may be insufficient. If the supply of the plasma medium is insufficient, the desired high-temperature plasma cannot be obtained, and the intensity of the obtained extreme ultraviolet light is reduced.

  In view of the above circumstances, the present invention provides a plasma light source capable of supplying an appropriate amount of plasma medium by preventing thermal damage of the medium holding unit and stably obtaining desired extreme ultraviolet light. Objective.

1st aspect of this invention is a plasma light source, Comprising: The rod-shaped center electrode extended on a single axis | shaft, The external electrode provided so that the outer periphery of the said center electrode might be enclosed, The said center electrode and the said external electrode A pair of coaxial electrodes that are opposed to each other across a plane of symmetry, generate plasma that emits extreme ultraviolet light, and confine the plasma, and on the side surfaces of the center electrode A medium holding unit that holds the plasma medium of the plasma, a voltage applying device that applies a discharge voltage to each of the coaxial electrodes, and ablation in the medium holding unit and a plasma sheet by the discharge voltage a laser device for irradiating a laser light for generating, by the optical element, thereby autonomously shifting the target position of the laser beam on the medium holding section And summarized in that and a location adjustment device.

The position adjusting device may be a device that shifts the target position in at least one of a circumferential direction of a central axis of the central electrode and a direction along the central axis of the central electrode.

  The laser device may irradiate the laser beam at a position symmetrical to the central axis of the central electrode of each of the coaxial electrodes.

According to a second aspect of the present invention, a rod-shaped center electrode extending on a single axis, an external electrode provided so as to surround the outer periphery of the center electrode, and the center electrode and the external electrode are insulated. This is an extreme ultraviolet light generation method using a pair of coaxial electrodes that have an insulator and are arranged opposite to each other across a plane of symmetry and generate plasma that emits extreme ultraviolet light and confine the plasma. In this method, a discharge voltage is applied to each of the coaxial electrodes, laser irradiation is performed on a medium holding portion that is provided on a side surface of the center electrode and includes the plasma medium of the plasma, thereby ablating the plasma medium. the discharge voltage to generate plasma sheet according to the gist that is autonomously shifts the target position location on the medium holding part of the laser light by the optical element performs.

  According to the present invention, it is possible to provide a plasma light source capable of supplying an appropriate amount of plasma medium by preventing thermal damage to the medium holding unit and stably obtaining desired extreme ultraviolet light.

It is a schematic block diagram (sectional drawing) of the plasma light source which concerns on 1st Embodiment of this invention. It is a figure which shows the electrical system for plasma light sources which concerns on 1st and 2nd embodiment of this invention. It is a figure which shows the III-III cross section of FIG. It is a figure which shows the shift operation of the target position and irradiation position in 1st Embodiment of this invention, (a) is a figure when moving a laser beam along the central axis of a center electrode, (b) is a center electrode. It is a figure when a laser beam is moved to the circumferential direction of the center axis | shaft. It is a schematic block diagram (partial cross section figure) of the plasma light source which concerns on 2nd Embodiment of this invention. It is a figure which shows the shift operation of the target position and irradiation position in 2nd Embodiment of this invention, (a) is a figure when a center electrode is operated in translation along the central axis, (b) is the center electrode. It is a figure when it rotates around a central axis.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram (cross-sectional view) of a plasma light source according to the present embodiment, and FIG. 2 is a diagram showing an electrical system of the plasma light source. As shown in these drawings, the plasma light source of the present embodiment includes a pair of coaxial electrodes 10 and 10, a reservoir 20 provided individually for each coaxial electrode 10, a voltage application device 30, and a laser device. 40 and a mirror 46 as a position adjusting device. In FIG. 1, the right coaxial electrode 10 has the same configuration as the left coaxial electrode 10, and thus detailed illustration is omitted.

  The pair of coaxial electrodes 10 and 10 are installed in a symmetrical positional relationship with the symmetry plane 1 in between in a vacuum chamber (not shown). In other words, the coaxial electrodes 10 are installed so as to face each other with a certain distance around the symmetry plane 1. The pair of coaxial electrodes 10 and 10 generate plasma 3 that emits extreme ultraviolet light, and confine the plasma 3 therebetween.

  Each coaxial electrode 10 includes a center electrode 12, a plurality of external electrodes 14, and an insulator 16. Between the center electrode 12 and the external electrode 14, a plasma medium 6 that emits extreme ultraviolet light is introduced from a medium holding unit 18 described later. The plasma medium 6 of this embodiment is a low-melting-point metal (low-melting-point alloy) that can be exposed on the side surface of the center electrode 12 in a liquid state, and the composition thereof is selected according to the necessary wavelength of ultraviolet rays. For example, Li or Sn is included when 13.5 nm ultraviolet light is required, and Bi or the like is included when 6.7 nm ultraviolet light is required.

  As shown in FIG. 1 and FIG. 3, the center electrode 12 has a single axis ZZ common to the coaxial electrodes 10 as a central axis (hereinafter, this axis is referred to as the central axis Z). It is a rod-shaped conductor extending on Z. The center electrode 12 includes a tip portion 12a facing the symmetry plane 1, a medium holding portion 18 provided behind the tip portion 12a (that is, a direction away from the symmetry plane 1 along the central axis Z), and a medium holding portion 18. And a base portion 12b provided at the rear of the reservoir, and protrudes from the reservoir 20 toward the symmetry plane 1. A flow path 12c of the plasma medium 6 is formed inside the base 12b. The channel 12 c communicates with the space 20 a in the reservoir 20 and is connected to the medium holding unit 18.

  The distal end portion 12a and the base portion 12b are formed using a material having heat resistance against high temperature plasma. Such a material is, for example, a refractory metal such as tungsten or molybdenum. The end surface of the front end portion 12a facing the symmetry plane 1 is a hemispherical curved surface. However, this shape is not essential, and a concave portion (not shown) may be provided on the end surface, or a simple flat surface. Further, since the base portion 12b is not exposed to a temperature as high as that of the tip portion 12a, the material is not limited to the above-described refractory metal, and may be copper having a high thermal conductivity.

  The medium holding unit 18 is a plasma medium region that holds and exposes the plasma medium 6 of the plasma 3 on the side surface of the center electrode 12. That is, the medium holding unit 18 holds the plasma medium 6 supplied from the reservoir 20 via the flow path 12 c in a liquid state and exposes the plasma medium 6 to the side surface of the center electrode 12. In order to have such a function, the medium holding part 18 is formed of a porous member having a hole diameter of about 10 to 100 μm. The porous member is made of a refractory metal and may be made of the same material as the center electrode 12. The surface of the medium holding unit 18 is irradiated with the laser beam 42 of the laser device 40, and the plasma medium 6 held by the medium holding unit 18 is ablated (see FIG. 1). The medium holding unit 18 may be formed entirely along the circumferential direction of the central axis Z or may be formed only at the irradiation position of the laser beam 42.

  The surface of the medium holding unit 18 is intermittently heated with a short period (for example, about 1 ms) due to ablation by the laser light 42. Also, starting from this ablation, an annular planar discharge 2 is generated, and then a final plasma 3 that emits extreme ultraviolet light is generated on the symmetry plane 1 (see FIG. 1). Therefore, the tip end portion 12a and the medium holding portion 18 are always exposed to high temperatures. In particular, since the tip 12a is close to the high temperature plasma 3, heating is remarkable. As a result, the temperature of the medium holding unit 18 rises due to the enormous heat from the tip 12a. The sheet discharge is a sheet discharge current that spreads two-dimensionally and is also called a current sheet or a plasma sheet.

  The reservoir 20 has a space 20a for storing the plasma medium 6 therein. The space 20 a communicates with the flow path 12 c of the center electrode 12. The reservoir 20 is provided with a heater 22. The heater 22 dissolves the plasma medium 6 and holds it in a liquid state. The heater 22 is composed of, for example, a heat medium (oil) circulation heater or an electrothermal heater. The plasma medium 6 dissolved in the space 20a by the heater 22 flows out to the medium holding part 18 through the flow path 12c.

  As shown in FIG. 1, the external electrode 14 is a rod-shaped conductor that extends parallel to the central axis Z of the central electrode 12. Also, as shown in FIG. 3, they are arranged at every angle θ along the circumferential direction of the center electrode 12 with a certain distance from the center electrode 12. In other words, each external electrode 14 is disposed in parallel with the center electrode 12 and surrounds the periphery of the center electrode 12. In the example shown in FIG. 3, six external electrodes 14 are arranged around the center electrode 12 every 60 °.

  As shown in FIG. 3, each external electrode 14 has a cross section including only one point G at which the distance from the center electrode 12 is shortest in a plane perpendicular to the axial direction. The cross section having such a shape is, for example, a circle. The cross-sectional shape of the external electrode 14 is not limited to this circular shape, and it is sufficient that at least the surface facing the center electrode 12 has a curved surface protruding toward the center electrode 12. In any case, the point G is arranged around the center electrode 12 at every angle θ.

  The external electrodes 14 are preferably arranged at equal intervals along the circumferential direction of the center electrode 12. For example, from the viewpoint of processing and assembly, each external electrode 14 is preferably installed at a rotationally symmetric position with respect to the center electrode 12. However, the present invention is not limited to such an arrangement. Further, the number of external electrodes 14 is not limited to six, and is appropriately set according to the size and shape of the center electrode 12 and the external electrode 14, the distance between them, and the like.

  The external electrode 14 is formed using a material having heat resistance against high-temperature plasma, like the center electrode 12. Further, the end face of the external electrode 14 facing the symmetry plane 1 may be either a curved surface or a flat surface.

  By arranging the plurality of external electrodes 14 around the center electrode 12 in this way, an initial discharge (for example, creeping discharge) of the planar discharge 2 can be generated between each external electrode 14 and the center electrode 12. it can. That is, by preferentially generating the initial discharge including each point G in the discharge path, it is possible to generate the initial discharge over the entire circumference of the center electrode 12, thereby forming the annular planar discharge 2. Becomes easier.

  The insulator 16 is formed using, for example, ceramic, supports the base portions of the center electrode 12 and the external electrode 14, defines the distance between them, and electrically insulates between them. The insulator 16 is formed in a disk shape, for example, and has a through hole through which the center electrode 12 and the external electrode 14 pass.

  Next, an electrical system in the plasma light source of this embodiment will be described. As shown in FIG. 2, the plasma light source includes a voltage applying device 30 connected to each coaxial electrode 10. The voltage application device 30 applies a discharge voltage having the same polarity to each coaxial electrode 10.

  The voltage application device 30 includes a high voltage power supply 32. The output side of the high-voltage power supply 32 is connected to the center electrode 12 of the coaxial electrode 10 and applies a positive discharge voltage higher than that of the external electrode 14 corresponding to the center electrode 12. Therefore, when the external electrode 14 is grounded, the potential of the center electrode 12 is positive.

  As described above, a plurality of external electrodes 14 are provided around each center electrode 12. In order to obtain an ideal sheet discharge 2, it is necessary to generate a discharge between all the external electrodes 14 and the center electrode 12. Moreover, it is desirable that these discharges are spatially distributed at equal intervals around the center electrode 12. For this reason, each external electrode 14 of the present embodiment has a surface facing the center electrode 12 as a curved surface to define a place where discharge is preferentially performed. However, even if the discharge location is fixed and the laser beam 42 described later is simultaneously applied to the medium holding portion 18 of each center electrode 12, the discharge between each external electrode 14 and the center electrode 12 can be generated strictly at the same time. In practice, there is a slight shift in the timing of occurrence of each discharge. The discharge energy supplied from the high-voltage power supply 32 tends to be preferentially consumed with respect to the first generated discharge. In this case, it is difficult to generate a plurality of discharges substantially simultaneously.

  Therefore, the voltage application device 30 of this embodiment includes an energy storage circuit 34 that stores the discharge energy of the discharge voltage for each external electrode 14. For example, as shown in FIG. 2, the energy storage circuit 34 includes a plurality of capacitors C that individually connect the center electrode 12 and each external electrode 14. Each capacitor C is connected to each output side and each common side of the high-voltage power supply 32.

  Thus, by providing the capacitor C for storing discharge energy for each external electrode 14, it is possible to generate discharge in all the external electrodes 14. That is, it is possible to prevent a large amount of discharge energy from being consumed by the first generated discharge, and to obtain an ideal planar discharge 2 generated over the entire circumference of the center electrode 12.

  Furthermore, the voltage application device 30 of this embodiment may include a discharge current blocking circuit 36 that blocks the discharge current from returning. For example, as shown in FIG. 2, the discharge current blocking circuit 36 includes an inductor L that connects each external electrode 14 and the voltage application device 30 (specifically, the common side of the high-voltage power supply 32). Since the inductor L has a sufficiently high impedance with respect to the discharge current, the discharge current that has passed through the center electrode 12 and the external electrode 14 can be returned to the energy storage circuit 34 that is the generation source thereof. That is, in order to prevent the discharge energy accumulated in each capacitor C from being supplied to the external electrode 14 other than the external electrode 14 directly connected to the capacitor C, the distribution of discharge in the circumferential direction of the center electrode 12 is biased. Can be prevented.

  As described above, the plasma light source of the present embodiment irradiates the surface of the central electrode 12 of each coaxial electrode 10 with laser light, thereby releasing the medium of the plasma 3 and the initial discharge of the plasma 3 (ie, the surface). A laser device 40 for generating a discharge 2). The laser device 40 is, for example, a YAG laser, and outputs a double wave of the fundamental wave as a short pulse laser beam 42 in order to perform ablation.

  As shown in FIG. 1, the laser beam 42 is branched by a beam splitter (half mirror) 44 and irradiated to the medium holding unit (plasma medium region) 18 of each center electrode 12. On the surface of the medium holding part 18 irradiated with the laser light 42, the plasma medium 6 is emitted as neutral gas or ions by ablation.

  The position adjusting device of the present invention will be described. The position adjusting device of the present invention relatively and automatically sets the target position 42a of the laser beam 42 on the medium holding unit 18 and the irradiation position 18a of the medium holding unit 18 irradiated with the laser beam 42 based on the target position 42a. Shift it. Here, the target position 42a is a position on the medium holding unit 18 determined by the optical path of the laser light 42, and the irradiation position 18a is a position after the target position 42a is irradiated with the laser light 42. If the target position 42a of the laser beam 42 is not changed, the target position 42a and the irradiation position 18a always indicate the same position.

  The position adjustment apparatus of the present embodiment includes an optical element that performs the shift described above. Specifically, as shown in FIG. 1, a movable (that is, angle adjustable) mirror 46 is provided as an optical element on the optical path of the laser light 42. A lens (not shown) for focusing the laser beam 42 on the medium holding unit 18 may be installed between the mirror 46 and the medium holding unit 18.

  FIG. 4 is a diagram illustrating a shift operation between the target position 42a and the irradiation position 18a in the present embodiment, and FIG. 4A is a diagram when the laser light 42 is moved along the central axis Z of the center electrode 12. FIG. (B) is a figure when the laser beam 42 is moved to the circumferential direction of the central axis Z of the center electrode 12. FIG. The mirror 46 defines an irradiation position 18 a that reflects the laser light 42 toward the medium holding unit 18. The reflection angle of the mirror 46 is set using a control unit (not shown) having a known angle adjustment mechanism. Further, the reflection angles of all the mirrors 46 are set synchronously. The moving speed of the target position 42a may be a speed at which the spots of the laser light 42 partially overlap.

  The reflection angle of the mirror 46 is such that the target position 42 a of the laser light 42 on the medium holding unit 18 is at least one of the circumferential direction of the central axis Z of the central electrode 12 and the direction along the central axis Z of the central electrode 12. It is automatically controlled to shift in the direction. That is, as shown in FIGS. 4A and 4B, the laser light 42 is on the medium holding portion 18 in the circumferential direction of the central axis Z and the direction along the central axis Z of the central electrode 12. Are swept (scanned) in at least one direction. The target position 42a may circulate through a predetermined route or may reciprocate. In any case, the irradiation position 18a moves gradually and does not remain at a fixed position.

  As described above, the irradiation position 18a by the laser light 42 gradually moves while the plasma light source is operating. Therefore, an excessive temperature rise at the irradiation position 18a when the irradiation position 18a is constant is suppressed. Furthermore, since the laser beam irradiation is performed on the region already filled with the plasma medium, the shortage of supply of the plasma medium is also solved.

  At the time of irradiation with the laser beam 42, the discharge voltage from the voltage application device 30 has already been applied between the center electrode 12 and the external electrode 14 of each coaxial electrode 10. Therefore, when the ablation described above occurs, a discharge between the center electrode 12 and each external electrode 14 is induced, and a planar discharge 2 (see FIG. 1) is formed by this discharge.

  In addition, the generation | occurrence | production location of the said discharge may be restrict | limited to the irradiation area | region of the laser beam 42, and its vicinity. Therefore, it is preferable that the laser device 40 irradiates the laser beam 42 at a position symmetric with respect to the center axis Z of each center electrode 12. This symmetry is maintained while shifting the target position 42a.

  This is based on an experimental result in which the region of the induced discharge has an opening angle of 180 degrees or more with the axis of the center electrode 12 as a base point. Note that simultaneous irradiation with a plurality of laser beams can be easily achieved by adjusting the optical path length.

  As described above, in the plasma light source of the present embodiment, a pair of coaxial electrodes 10 are provided in a vacuum chamber (not shown). The pair of coaxial electrodes 10 are disposed to face each other with the symmetry plane 1 in between. On the other hand, the inside of the vacuum chamber is maintained at a temperature and pressure suitable for generating the plasma 3. In addition, a discharge voltage having the same polarity is applied to each coaxial electrode 10 before discharge by the voltage application device 30.

  As shown in FIG. 1, the laser beam 42 is simultaneously irradiated to the medium holding portion 18 of each coaxial electrode 10 in a state where a discharge voltage is applied. Immediately thereafter, an initial discharge occurs between the center electrode 12 and each external electrode 14. Thereafter, a planar discharge 2 in which the discharge is distributed over the entire circumference of the center electrode 12 is obtained. By forming the planar discharge 2, the gas or ions containing Li are released from the medium holding unit 18 in each coaxial electrode 10.

  As shown in FIG. 1, the planar discharge 2 moves in a direction (direction toward the symmetry plane 1) discharged from the electrode by the self magnetic field. The planar discharge 2 at this time is distributed in a substantially annular shape as viewed from the axis ZZ.

  When the planar discharge 2 reaches the tip of the coaxial electrode 10, the starting point of the discharge current of the planar discharge 2 is forcibly shifted from the circumferential side surface of the center electrode 12 to the tip 12a. In other words, the discharge current flows intensively from the tip 12a. Due to the pinch effect caused by this current concentration, the current density around the tip 12a rapidly increases, and the plasma medium 6 including Li around the tip 12a sandwiched between the pair of planar discharges 2 has a high density and a high temperature. Become.

  Further, since this phenomenon proceeds at each coaxial electrode 10 across the symmetry plane 1, the plasma medium 6 is pushed out from one coaxial electrode 10 toward the other coaxial electrode 10. As a result, the plasma medium 6 receives electromagnetic pressure from both directions along the axis ZZ (center axis Z) and moves to an intermediate position where each coaxial electrode 10 faces (that is, the symmetry plane 1 of the center electrode 12). Thus, a single plasma 3 having the plasma medium 6 as a component is formed.

  As described above, while the sheet discharge 2 is generated, the current of each sheet discharge 2 is concentrated on the front end portion 12a of each center electrode 12. Accordingly, a pinch effect toward the axis ZZ acts on the plasma 3 around the front end portion 12a, and the density and temperature of the plasma 3 increase. That is, ionization of the plasma medium 6 proceeds. As a result, plasma light 8 including extreme ultraviolet light is emitted from the plasma 3. In this state, the voltage application device 30 continues to supply energy corresponding to the light emission energy of the plasma 3. With this energy supply, the plasma light 8 can be generated for a long time with high energy conversion efficiency.

  In the plasma light source of the present embodiment, the target position 42 a is gradually shifted with respect to the irradiation position of the medium holding unit 18. Therefore, since the irradiation position 18a is also gradually shifted, an excessive temperature rise at the irradiation position 18a when the irradiation position 18a is constant is suppressed, and laser light irradiation is performed on a region already filled with the plasma medium. The shortage of media supply is also resolved. That is, since it is avoided that the laser beam 42 is irradiated with the medium holding unit 18 exposed, thermal damage to the medium holding unit 18 due to the laser beam 42 can be prevented. Since the thermal damage to the medium holding unit 18 can be prevented, the life of the medium holding unit 18 is extended, and the plasma medium can be stably held and an appropriate amount of evaporation can be achieved over a long period of time. As a result, extreme ultraviolet light having a constant intensity can be stably obtained over a desired exposure time.

(Second Embodiment)
A second embodiment of the present invention will be described. FIG. 5 is a schematic configuration diagram (cross-sectional view) of the plasma light source according to the present embodiment, FIG. 6 is a diagram illustrating a shift operation of the target position 42a and the irradiation position 18a in the present embodiment, and FIG. (B) is a diagram when the center electrode 12 is rotated around the central axis Z. FIG. The plasma light source of the present embodiment includes a support mechanism 24 and a control unit (not shown) having a known drive mechanism as a position adjusting device that performs the above-described shift. The support mechanism 24 is constituted by, for example, a known rotation introducer or a linear rotation introducer, and supports the center electrode 12 so as to be rotatable around the center axis Z thereof. This rotation is automatically controlled by a control unit (not shown). The support mechanism 24 may support the center electrode 12 so as to be movable along the center axis Z, or may support the center electrode 12 by a combination thereof. In the former case, the support mechanism 24 is constituted by a known linear introducer, and in the latter case, the support mechanism 24 is constituted by a known linear rotation introducer. Further, when the plasma light source is in operation, the angle of the mirror 46 is fixed. Other configurations are the same as those in the first embodiment, and thus the description thereof is omitted.

  As shown in FIG. 5, the support mechanism 24 of the present embodiment supports the central electrode 12 indirectly by supporting the reservoir 20. The position of the reservoir 20 is arbitrary as long as an appropriate flow of the plasma medium 6 to the medium holding unit 18 can be ensured. Therefore, the support mechanism 24 may be configured and arranged to directly support the center electrode 12.

  In the present embodiment, the target position 42a of the laser beam 42 is fixed. As shown in FIGS. 6A and 6B, the target position 42a is preferably set at a symmetrical position with respect to the central axis Z of each center electrode 12. On the other hand, the support mechanism 24 moves the center electrode 12 along the center axis Z (see FIG. 6A). Alternatively, the support mechanism 24 rotates the center electrode 12 around the center axis Z (see FIG. 6B). Furthermore, the support mechanism 24 may perform these rotations and translational movements simultaneously. Accordingly, the irradiation position 18 a on the medium holding unit 18 is shifted in at least one of the circumferential direction of the central axis Z of the central electrode 12 and the direction along the central axis Z of the central electrode 12. As a result, as in the first embodiment, a relative shift between the target position 42a and the irradiation position 18a is achieved, and the same effect as in the first embodiment can be obtained in the second embodiment. It should be noted that this embodiment and the first embodiment described above can be combined. In this case, the same effect as that of the first embodiment can be obtained.

  In addition, this invention is not limited to embodiment mentioned above, is shown by description of a claim, and also includes all the changes within the meaning and range equivalent to description of a claim.

1 Symmetrical plane 2 Planar discharge (plasma sheet)
DESCRIPTION OF SYMBOLS 3 Plasma 6 Plasma medium 8 Plasma light 10 Coaxial electrode 12 Center electrode 14 External electrode 16 Insulator 18 Medium holding | maintenance part 18a Irradiation position 20 Reservoir 24 Support mechanism 30 Voltage application apparatus 40 Laser apparatus 42 Laser beam 42a Target position 46 Mirror (movable) formula)

Claims (4)

A bar-shaped center electrode extending on a single axis, an external electrode provided so as to surround the outer periphery of the center electrode, and an insulator that insulates between the center electrode and the external electrode, and has a symmetry plane A pair of coaxial electrodes disposed opposite to each other, generating plasma that emits extreme ultraviolet light and confining the plasma;
A medium holding part that is provided on a side surface of the central electrode and holds the plasma medium of the plasma;
A voltage applying device for applying a discharge voltage to each of the coaxial electrodes;
A laser device for performing ablation in the medium holding unit and irradiating a laser beam for generating a plasma sheet by the discharge voltage;
A plasma light source comprising: a position adjusting device that autonomously shifts a target position of the laser beam on the medium holding unit by an optical element . The position adjusting device is a device that shifts the target position in at least one of a circumferential direction of a central axis of the central electrode and a direction along the central axis of the central electrode. Item 2. The plasma light source according to Item 1. 3. The plasma light source according to claim 1 , wherein the laser device irradiates the laser light at a position symmetric with respect to a central axis of the central electrode of each of the coaxial electrodes . A bar-shaped center electrode extending on a single axis, an external electrode provided so as to surround the outer periphery of the center electrode, and an insulator that insulates between the center electrode and the external electrode, and has a symmetry plane In a method of generating extreme ultraviolet light using a pair of coaxial electrodes that are arranged opposite to each other and generate plasma that emits extreme ultraviolet light and confine the plasma,
  Applying a discharge voltage to each of the coaxial electrodes,
  A plasma sheet is generated by the discharge voltage while ablating the plasma medium by irradiating a laser beam onto a medium holding part including the plasma medium of the plasma, provided on a side surface of the center electrode,
  A method of generating extreme ultraviolet light, wherein an optical element autonomously shifts a target position of the laser light on the medium holding unit.

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