JP2011222186A - Plasma light source and plasma light generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma light source that (1) stabilizes plasma light of EUV emission for a long time, (2) has a large emission solid angle,(3) continuously supplies a plasma medium,(4) increases output and reduces discharge jitters, and (5) prevents impurities from being in plasma to enhance conversion efficiency.SOLUTION: The plasma light source includes a pair of coaxial electrodes 10 whose center electrodes have their axially inner ends arranged opposite each other, a discharge environment holding device 20 which holds temperature and pressure in the pair of coaxial electrodes, and a voltage application device 30 which applies discharging voltages to the respective coaxial electrodes. Insulating members 16 are arranged in contact with external surfaces of the center electrodes 12 or internal surfaces of guide electrodes 14 symmetrically with respect to an axis Z-Z, and have a plurality of grooves through which a plasma metal of liquid metal seeps out. A tubular discharge is generated between the coaxial electrodes by surface discharges between the center electrodes and guide electrodes that are generated with the plasma medium of the liquid metal supplied through the grooves as discharge start pins, thereby confining plasma in the axial direction.

Description

  The present invention relates to a plasma light source and a method for generating plasma light for EUV radiation.

  Lithography using an extreme ultraviolet light source is expected for fine processing of next-generation semiconductors. Lithography is a technique for forming an electronic circuit by exposing a resist material to light and a beam by reducing and projecting them onto a silicon substrate through a mask on which a circuit pattern is drawn. The minimum processing dimension of a circuit formed by photolithography basically depends on the wavelength of the light source. Therefore, it is essential to shorten the wavelength of the light source for next-generation semiconductor development, and research for this light source development is underway.

  The most promising next generation lithography light source is an extreme ultraviolet light source (EUV: Extreme Ultra Violet), which means light in the wavelength region of approximately 1 to 100 nm. The light in this region has a high absorptance with respect to all substances, and a transmissive optical system such as a lens cannot be used. Therefore, a reflective optical system is used. In addition, the optical system in the extreme ultraviolet region is very difficult to develop, and exhibits a reflection characteristic only at a limited wavelength.

  Currently, a Mo / Si multilayer reflector having a sensitivity of 13.5 nm has been developed, and it is expected that a processing dimension of 30 nm or less can be realized if a lithography technique combining light of this wavelength and the reflector is developed. ing. Development of a lithography light source with a wavelength of 13.5 nm is urgently required to realize further microfabrication technology, and radiation from a high energy density plasma has attracted attention.

  The light source plasma generation can be broadly classified into a laser irradiation method (LPP: Laser Produced Plasma) and a gas discharge method (DPP: Discharge Produced Plasma) driven by a pulse power technique. The gas discharge method (DPP) is advantageous in that the input power is directly converted into plasma energy, so that the conversion efficiency is superior to that of LPP, and the apparatus is small in size and low in cost.

The conversion efficiency (plasma conversion E. science: PCE) from the plasma to the radiation in the effective wavelength region (in-band) is expressed by the following equation (1).
P. C. E = (P _inband × τ) / E (1)
Here, P _inband is the EUV radiation output in the effective wavelength region, τ is the radiation duration, and E is the energy input to the plasma.

Xe, Sn, Li and the like are typical elements having a radiation spectrum in the effective wavelength region, and research has been progressed mainly on Xe in the early stages of development because of ease of experimentation and ease of handling. However, in recent years, Sn has been attracting attention and research is being promoted because of its high output and high efficiency. In addition, expectation for hydrogen-like Li ions (Li ²⁺ ) having just a Lyman-α resonance line in the effective wavelength region is increasing.

The radiation spectrum from a high-temperature, high-density plasma is basically determined by the temperature and density of the target material. According to the calculation result of the atomic process of the plasma, the electron in the case of Xe, Sn is used to make the plasma in the EUV radiation region. The optimum temperature and electron density are several tens of eV and about 10 ¹⁸ cm ⁻³ , respectively, and in the case of Li, about 20 eV and 10 ¹⁸ cm ⁻³ are optimum.

  The plasma light source described above is disclosed in Non-Patent Documents 1 and 2 and Patent Documents 1 and 2.

Hiroto Sato et al., “Discharge Plasma EUV Light Source for Lithography”, OQD-08-28 Jeroen Jonkers, “High power extreme-violet (EUV) light sources for future lithography”, Plasma Sources Science and Technology 16 (Science 16)

JP 2000-509190 A, “Method and apparatus for generating X-ray radiation or extreme ultraviolet radiation” Japanese Patent Application Laid-Open No. 2004-226244, “Extreme Ultraviolet Light Source and Semiconductor Exposure Apparatus”

  An EUV lithography light source is required to have a high average output, a small light source size, a small amount of scattered particles (debris), and the like. At present, the EUV emission amount is extremely low with respect to the required output, and increasing the output is one of the major issues. On the other hand, if the input energy is increased for increasing the output, the damage caused by the thermal load will be caused by the plasma generator and The lifetime of the optical system is reduced. Therefore, high energy conversion efficiency is indispensable to satisfy both high EUV output and low heat load.

  In the initial stage of plasma formation, in addition to consuming a lot of energy for heating and ionization, high-temperature and high-density plasma that emits EUV generally expands rapidly, so the radiation duration τ is extremely short. . Therefore, in order to improve the conversion efficiency, it is important to maintain the plasma in a high temperature and high density state suitable for EUV radiation for a long time (on the order of μsec).

  Room-temperature solid media such as Sn and Li have high spectral conversion efficiency, but the plasma generation is accompanied by phase changes such as melting and evaporation, so the effect of contamination inside the device due to debris (derived from discharge) such as neutral particles Becomes larger. Therefore, the target supply and recovery system must be strengthened as well.

  The radiation time of the current general EUV plasma light source is about 100 nsec, and the output is extremely insufficient. In order to achieve both high conversion efficiency and high average output for industrial applications, it is necessary to achieve an EUV radiation time of several μsec (at least 1 μsec or more) in one shot. In other words, in order to develop a plasma light source having high conversion efficiency, it is necessary to restrain plasma in a temperature density state suitable for each target for 1 μsec or more to achieve stable EUV radiation.

  Furthermore, the conventional capillary discharge has a drawback that the effective radiation solid angle is small because the plasma is confined in the capillary.

Further, in the gas discharge method (DPP), in order to stably generate a discharge between electrodes, discharge jitter is reduced by irradiating a laser beam to a discharge start position in synchronization with the timing of applying a discharge voltage. be able to. In particular, symmetrical discharge can be generated by multi-point irradiation with laser light. On the other hand, there is a problem that the device structure is complicated and the device cost is significantly increased.
Further, in the case of multi-point irradiation with laser light, since a large number of laser optical systems are installed, there is a problem that the effective solid angle at which the generated EUV light can be condensed becomes small, and the utilization efficiency of EUV light is reduced.

  On the other hand, in order to increase the output of EUV light, it is conceivable to arrange a plurality of metal pins as discharge starting points symmetrically as a means for simultaneously generating discharge at a plurality of locations and reducing discharge jitter. However, with this means, the metal pin is severely damaged by electric discharge and cannot operate stably for a long time. Further, this means has a problem that the efficiency of conversion to effective EUV light in the vicinity of 13.5 nm is lowered because the evaporated metal pin substance is mixed as impurities in the light source plasma.

  The present invention has been developed to solve such problems. That is, the object of the present invention is to stably generate plasma light for EUV radiation for a long time (on the order of μsec), to increase the effective solid angle of the generated plasma light, and to make the plasma medium continuous. Plasma light source that can increase the output of EUV light, reduce discharge jitter, prevent impurities mixed in the light source plasma and increase the efficiency of conversion to effective EUV light And providing a method for generating plasma light.

According to the present invention, a rod-shaped center electrode extending on a single axis, a tubular guide electrode that surrounds the center electrode at a predetermined interval, and an axially outer end portion of the center electrode and the guide electrode are positioned. A pair of coaxial electrodes, each of which is formed by a ring-shaped insulating member that insulates between them, wherein the inner ends in the axial direction of the central electrode are opposed to each other with a gap therebetween,
A discharge environment holding device for holding the inside of the pair of coaxial electrodes at a temperature and pressure suitable for plasma generation;
A voltage applying device that applies a discharge voltage with the polarity reversed to each of the coaxial electrodes, and
The plasma light source is characterized in that the insulating member has a plurality of grooves that are in close contact with the outer surface of the center electrode or the inner surface of the guide electrode and ooze the liquid metal plasma medium to the inner end surface in the axial direction. Provided.

According to a preferred embodiment of the present invention, the insulating member is electrically insulated from the center electrode and the guide electrode, and a plasma medium supply unit that supplies a plasma medium to an inner end surface in the axial direction thereof;
An inner insulating tube and an outer insulating tube that insulate between the plasma medium supply unit and the center electrode and the guide electrode;
The plurality of grooves are arranged symmetrically with respect to the single axis on the inner surface of the inner insulating tube or the outer surface of the outer insulating tube.

  The plasma medium is preferably lithium or tin.

Further, according to the present invention, (A) a rod-shaped center electrode extending on a single axis, a tubular guide electrode surrounding the center electrode at a predetermined interval, and an axially outside of the center electrode and the guide electrode A ring-shaped insulating member that is located at an end portion and insulates between them, and prepares a pair of coaxial electrodes in which the inner end portions in the axial direction of the center electrode are arranged to face each other with a gap therebetween,
The insulating member has a plurality of grooves that are in close contact with the outer surface of the center electrode or the inner surface of the guide electrode and ooze the liquid metal plasma medium to the inner end surface in the axial direction.
(B) maintaining the temperature and pressure suitable for plasma generation in the pair of coaxial electrodes;
(C) Applying a discharge voltage with the polarity reversed between the center electrode and the guide electrode of each coaxial electrode, and supplying a pair of coaxial electrodes to the pair of coaxial electrodes via the groove, respectively. A sheet discharge is generated between the center electrode and the guide electrode serving as a discharge start pin, and the sheet discharge forms a single plasma at the opposite intermediate position of each coaxial electrode,
(D) The planar discharge is then switched to a tubular discharge between a pair of coaxial electrodes to contain the plasma in the axial direction,
(E) A plasma light generating method is provided, wherein plasma light is generated between the coaxial electrodes by supplying energy corresponding to plasma emission energy from the coaxial electrodes.

According to the apparatus and method of the present invention, the insulating member between the center electrode and the guide electrode has a plurality of grooves that are in close contact with the outer surface of the center electrode or the inner surface of the guide electrode. Due to the phenomenon, the liquid metal plasma medium can ooze out to the inner end face in the axial direction.
Since the liquid metal that has oozed to the inner end face in the axial direction has the same potential as the center electrode or the guide electrode, when a discharge voltage is applied between the center electrode and the guide electrode, a plurality of liquid metals (plasma media) serve as discharge start pins. Function.

  Further, since the plurality of grooves are arranged symmetrically with respect to the single axis, the liquid metal (lithium or tin) oozed out in a symmetrical arrangement on the outer peripheral portion of the center electrode (or the inner peripheral portion of the guide electrode) Acts as a plurality of symmetrically arranged discharge start pins, and can stably perform symmetric planar discharge.

  Furthermore, since the liquid metal is continuously supplied through a plurality of grooves, it does not wear even if it acts as a discharge start pin, and can be operated repeatedly for a long time.

  Further, although the liquid metal evaporates due to electric discharge, since the evaporated metal itself is a plasma medium (lithium or tin), there is no possibility that impurities are mixed into the plasma medium.

  Furthermore, plasma light is generated between the coaxial electrodes, and no special equipment is required around the light emitting point. Therefore, compared to multi-point irradiation with laser light, the generated EUV light can be collected more effectively. The solid angle can be increased, and the utilization efficiency of EUV light can be increased.

  Therefore, the effective radiation solid angle of the generated plasma light can be increased, the EUV light output can be increased and the discharge jitter can be reduced, and impurities mixed in the light source plasma can be prevented and converted into effective EUV light. Efficiency can be increased.

In addition, a plasma medium supply unit that is electrically insulated from the center electrode and the guide electrode is provided, and the plasma medium is supplied to the inner end face in the axial direction. Therefore, plasma light for EUV radiation is emitted for a long time (on the order of μsec). It can generate stably and can supply a plasma medium continuously.

It is a whole block diagram of the plasma light source by this invention. It is a block diagram of the coaxial electrode in FIG. It is operation | movement explanatory drawing of the plasma light source by this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail 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.

FIG. 1 is an overall configuration diagram of a plasma light source according to the present invention.
In this figure, the plasma light source of the present invention includes a pair of coaxial electrodes 10, a discharge environment holding device 20, and a voltage application device 30.

The pair of coaxial electrodes 10 are disposed opposite to each other with the symmetry plane 1 as the center.
Each coaxial electrode 10 includes a rod-shaped center electrode 12, a tubular guide electrode 14, and a ring-shaped insulating member 16.

The rod-shaped center electrode 12 is a conductive electrode extending on a single axis ZZ.
In this example, the end surface of the center electrode 12 facing the symmetry plane 1 is a flat surface, but may be provided with a concave hole or may be arcuate.

  The tubular guide electrode 14 surrounds the central electrode 12 with a certain interval, and holds a plasma medium therebetween. The end face of the guide electrode 14 facing the symmetry plane 1 may be arcuate or flat.

  The ring-shaped insulating member 16 is an electrical insulator having a hollow cylindrical shape as a whole located at the axially outer ends of the center electrode 12 and the guide electrode 14, and electrically between the center electrode 12 and the guide electrode 14. Insulate.

  In the pair of coaxial electrodes 10 described above, the center electrodes 12 are positioned on the same axis ZZ, and the inner ends in the axial direction of the center electrodes 12 are disposed to face each other with a certain distance therebetween. It is located symmetrically.

The discharge environment holding device 20 holds the coaxial electrode 10 at a temperature and pressure suitable for plasma generation in the coaxial electrode 10.
The discharge environment holding device 20 can be constituted by, for example, a vacuum chamber, a temperature controller, a vacuum device, and a plasma medium supply device. This configuration is not essential, and other configurations may be used.

The voltage application device 30 applies a discharge voltage with the polarity reversed to each coaxial electrode 10.
In this example, the voltage application device 30 includes a positive voltage source 32, a negative voltage source 34, and a trigger switch 36.
The positive voltage source 32 applies a positive discharge voltage higher than that of the guide electrode 14 to the center electrode 12 of the coaxial electrode 10 on one side (left side in this example).
The negative voltage source 34 applies a negative discharge voltage lower than that of the guide electrode 14 to the center electrode 12 of the other coaxial electrode 10 (right side in this example).
The trigger switch 36 simultaneously activates the positive voltage source 32 and the negative voltage source 34 to apply positive and negative discharge voltages to the respective coaxial electrodes 12 simultaneously.
With this configuration, the plasma light source of the present invention forms a tubular discharge (described later) between the pair of coaxial electrodes 10 to contain the plasma in the axial direction.

FIG. 2 is a configuration diagram of the coaxial electrode in FIG. In this figure, (A) is a side view showing only one (left side) of the pair of coaxial electrodes 10 described above, and (B) is a BB cross-sectional view thereof.
In this figure, the insulating member 16 is in close contact with the outer surface of the center electrode 12 (or the inner surface of the guide electrode 14), and a plurality (eight in this example) arranged symmetrically with respect to a single axis ZZ. ) Groove 16a. The groove 16a is so fine that the liquid metal plasma medium 6 causes a capillary phenomenon, and the liquid metal plasma medium 6 oozes out to the inner end face in the axial direction by the capillary phenomenon.

  In FIG. 2, the insulating member 16 includes a plasma medium supply unit 16b, an inner insulating tube 16c, and an outer insulating tube 16d.

The plasma medium supply part 16b is a porous ceramic in this example. In addition, a main medium supply device 18 is provided on the inner end surface in the axial direction of the plasma medium supply unit 16b.
The main medium supply device 18 is provided in close contact with the inner end surface in the axial direction of the plasma medium supply unit 16b, and supplies the plasma medium 6 to the inner end surface in the axial direction through the plasma medium supply unit 16b.
In this example, the main medium supply device 18 includes a main reservoir 18a (for example, a crucible) that holds the plasma medium 6 therein, and a main heating device 18b that heats and liquefies the plasma medium. The main heating device 18b is connected to a power source (not shown) so that the heating rate can be controlled.
The plasma medium 6 on the inner end surface in the axial direction of the plasma medium supply unit 16b is a liquid or a gas.

  The inner insulating tube 16 c and the outer insulating tube 16 d insulate the plasma medium supply unit 16 b from the center electrode 12 and the guide electrode 14. The inner insulating tube 16c and the outer insulating tube 16d are, for example, dense ceramic.

The plurality of grooves 16a are arranged symmetrically with respect to a single axis ZZ on the inner surface of the inner insulating tube 16c (or the outer surface of the outer insulating tube 16d). Further, an auxiliary medium supply device 19 is provided on the inner end surface in the axial direction of the groove 16a.
The auxiliary medium supply device 19 is provided in close contact with the inner end face in the axial direction of the groove 16a, and supplies the plasma medium 6 to the inner end face in the axial direction through the groove 16a.
In this example, the auxiliary medium supply device 19 includes an auxiliary reservoir 19a (for example, a crucible) that holds the plasma medium 6 therein, and an auxiliary heating device 19b that heats and liquefies the plasma medium. The auxiliary heating device 19b is connected to a power source (not shown) so that the heating rate can be controlled.
The plasma medium 6 on the inner end surface in the axial direction of the groove 16a is a liquid.

The main medium supply device 18 and the auxiliary medium supply device 19 may have different configurations as long as they are electrically insulated from each other and can supply the plasma medium 6 independently.
The plasma medium 6 by the main medium supply device 18 and the auxiliary medium supply device 19 is preferably the same lithium or tin.

FIG. 3 is an operation explanatory view of the plasma light source according to the present invention. In this figure, (A) shows the occurrence of a planar discharge, (B) shows the movement of the planar discharge, (C) shows the formation of plasma, and (D) shows the formation of a plasma confining magnetic field. .
Hereinafter, the plasma light generation method of the present invention will be described with reference to this drawing. In this figure, the discharge environment holding device 20 and the voltage application device 30 are omitted.

  In the plasma light generating method of the present invention, the pair of coaxial electrodes 10 described above are arranged to face each other, and the inside of the coaxial electrode 10 is held at a temperature and pressure suitable for plasma generation by the discharge environment holding device 20. A discharge voltage with the polarity reversed is applied to each coaxial electrode 10 by 30.

As shown in FIG. 3A, by applying this voltage, the liquid metal plasma medium 6 supplied to the pair of coaxial electrodes 10 through the grooves 16a on the surface of the insulating member 16 is used as a discharge start pin. A planar discharge current (hereinafter referred to as planar discharge 2) between the electrode 12 and the guide electrode 14 is generated. The planar discharge 2 is a planar discharge current that spreads two-dimensionally.
The “discharge start pin” means a conductor that functions as a discharge electrode when starting discharge.

At this time, the center electrode 12 of the left coaxial electrode 10 is applied with a positive voltage (+), the guide electrode 14 is applied with a negative voltage (−), and the center electrode 12 of the right coaxial electrode 10 is applied with a negative voltage (−). The guide electrode 14 is applied to a positive voltage (+).
Alternatively, both guide electrodes 14 may be grounded and held at 0 V, one center electrode 12 may be applied to a positive voltage (+), and the other center electrode 12 may be applied to a negative voltage (−).

  In the present invention, since the plurality of fine grooves 16a are arranged symmetrically with respect to the single axis ZZ, they ooze out in a symmetrical arrangement with respect to the outer peripheral portion of the center electrode (or the inner peripheral portion of the guide electrode). The liquid metal (lithium or tin) acts as a plurality of discharge start pins having a symmetrical arrangement, and can perform a symmetrical planar discharge stably.

  As shown in FIG. 3B, the planar discharge 2 moves in a direction (direction toward the center in the figure) discharged from the electrode by the self magnetic field.

  As shown in FIG. 3C, when the sheet discharge 2 reaches the tip of the pair of coaxial electrodes 10, the plasma medium 6 sandwiched between the pair of sheet discharges 2 becomes high density and high temperature. A single plasma 3 is formed at an intermediate position (symmetric surface 1 of the center electrode 12) of the coaxial electrodes 10 facing each other.

Further, in this state, the pair of opposed center electrodes 12 are a positive voltage (+) and a negative voltage (−), and similarly, the pair of opposed guide electrodes 14 are also a positive voltage (+) and a negative voltage. Since (−), as shown in FIG. 3D, the planar discharge 2 is transformed into a tubular discharge 4 that discharges between a pair of opposed center electrodes 12 and between a pair of opposed guide electrodes 14. It can be reconnected. Here, the tubular discharge 4 means a hollow cylindrical discharge current surrounding the axis ZZ.
When this tubular discharge 4 is formed, a plasma containment magnetic field (magnetic bin) indicated by reference numeral 5 in the figure is formed, and the plasma 3 can be contained in the radial direction and the axial direction.

That is, the central portion of the magnetic bin 5 is large due to the pressure of the plasma 3 and both sides thereof are small, and a magnetic pressure gradient in the axial direction toward the plasma 3 is formed. The plasma 3 is constrained to an intermediate position by this magnetic pressure gradient. Furthermore, the plasma 3 is compressed (Z pinch) in the center direction by the self-magnetic field of the plasma current, and the restraint by the self-magnetic field also acts in the radial direction.
In this state, if the energy corresponding to the emission energy of the plasma 3 is continuously supplied from the voltage application device 30, the plasma light 8 (EUV) can be stably generated for a long time with high energy conversion efficiency.

According to the apparatus and method of the present invention described above, the insulating member 16 between the center electrode 12 and the guide electrode 14 has the plurality of grooves 16a that are in close contact with the outer surface of the center electrode 12 (or the inner surface of the guide electrode 14). The liquid metal plasma medium 6 can ooze out to the inner end face in the axial direction by capillary action through the plurality of grooves 16a.
Since the liquid metal that has oozed out to the inner end face in the axial direction has the same potential as the center electrode 12 (or guide electrode), when a discharge voltage is applied between the center electrode 12 and the guide electrode 14, a plurality of liquid metals (plasma medium 6) are used. ) Functions as a discharge start pin.

  Further, since the plurality of grooves 16a are arranged symmetrically with respect to the single axis ZZ, the liquid metal (lithium) oozed out in a symmetrical arrangement with respect to the outer peripheral portion of the center electrode (or the inner peripheral portion of the guide electrode). Or tin) acts as a plurality of discharge start pins having a symmetrical arrangement, and can perform a symmetrical planar discharge stably.

  Furthermore, since the liquid metal is continuously supplied through the plurality of grooves 16a, it does not wear even if it acts as a discharge start pin, and can be operated repeatedly for a long time.

  Further, although the liquid metal evaporates due to electric discharge, since the evaporated metal itself is the plasma medium 6 (lithium or tin), there is no possibility that impurities are mixed into the plasma medium 6.

  Furthermore, plasma light is generated between the coaxial electrodes, and no special equipment is required around the light emitting point. Therefore, compared to multi-point irradiation with laser light, the generated EUV light can be collected more effectively. The solid angle can be increased, and the utilization efficiency of EUV light can be increased.

  Therefore, the effective radiation solid angle of the generated plasma light can be increased, the EUV light output can be increased and the discharge jitter can be reduced, and impurities mixed in the light source plasma can be prevented and converted into effective EUV light. Efficiency can be increased.

  In addition, a plasma medium supply unit that is electrically insulated from the center electrode and the guide electrode is provided, and the plasma medium is supplied to the inner end face in the axial direction. Therefore, plasma light for EUV radiation is emitted for a long time (on the order of μsec). It can generate stably and can supply a plasma medium continuously.

  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 symmetry plane, 2 planar discharge, 3 plasma,
4 Tubular discharge, 5 plasma containment magnetic field,
6 plasma medium, 8 plasma light (EUV light),
10 coaxial electrode, 12 center electrode,
14 guide electrodes, 16 insulating members,
16a groove, 16b plasma medium supply unit,
16c inner insulating tube, 16d outer insulating tube,
18 Main medium supply device,
18a main reservoir, 18b main heating device,
19 Auxiliary medium supply device,
19a auxiliary reservoir, 19b auxiliary heating device,
20 discharge environment holding device, 30 voltage application device,
32 Positive voltage source, 34 Negative voltage source, 36 Trigger switch

Claims (4)

A rod-shaped center electrode extending on a single axis, a tubular guide electrode surrounding the center electrode at a predetermined interval, and a ring located at an axially outer end of the center electrode and the guide electrode and insulating between them A pair of coaxial electrodes, the inner ends of the central electrode being opposed to each other with a gap therebetween,
A discharge environment holding device for holding the inside of the pair of coaxial electrodes at a temperature and pressure suitable for plasma generation;
A voltage applying device that applies a discharge voltage with the polarity reversed to each of the coaxial electrodes, and
The plasma light source, wherein the insulating member has a plurality of grooves that are in close contact with the outer surface of the central electrode or the inner surface of the guide electrode and allow the liquid metal plasma medium to ooze out to the inner end surface in the axial direction. The insulating member is electrically insulated from the center electrode and the guide electrode, and a plasma medium supply unit that supplies a plasma medium to an axially inner end surface thereof;
An inner insulating tube and an outer insulating tube that insulate between the plasma medium supply unit and the center electrode and the guide electrode;
2. The plasma light source according to claim 1, wherein the plurality of grooves are arranged symmetrically with respect to the single axis on the inner surface of the inner insulating tube or the outer surface of the outer insulating tube.   The plasma light source according to claim 1, wherein the plasma medium is lithium or tin. (A) A rod-shaped center electrode extending on a single axis, a tubular guide electrode surrounding the center electrode at a certain interval, and an axial end portion between the center electrode and the guide electrode. A ring-shaped insulating member that insulates, and preparing a pair of coaxial electrodes in which the axially inner end portions of the center electrode are opposed to each other with a gap therebetween,
The insulating member has a plurality of grooves that are in close contact with the outer surface of the center electrode or the inner surface of the guide electrode and ooze the liquid metal plasma medium to the inner end surface in the axial direction.
(B) maintaining the temperature and pressure suitable for plasma generation in the pair of coaxial electrodes;
(C) Applying a discharge voltage with the polarity reversed between the center electrode and the guide electrode of each coaxial electrode, and supplying a pair of coaxial electrodes to the pair of coaxial electrodes via the groove, respectively. A sheet discharge is generated between the center electrode and the guide electrode serving as a discharge start pin, and the sheet discharge forms a single plasma at the opposite intermediate position of each coaxial electrode,
(D) The planar discharge is then switched to a tubular discharge between a pair of coaxial electrodes to contain the plasma in the axial direction,
(E) A plasma light generation method characterized in that plasma light is generated between the coaxial electrodes by supplying energy corresponding to plasma emission energy from each coaxial electrode.