JP2012191040A - Plasma light source system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma light source system which can extend the lifetime of device by minimizing damage due to thermal load even when the output of plasma light generated is increased significantly.SOLUTION: In a vacuum chamber 21 which is evacuated internally, the plasma light source system comprises: a plurality of plasma light sources 10 emitting plasma light 8 periodically at a plurality of light-emitting points 1a set on the circumference of a circle centered on a central axis 7; a mirror rotating body 40 which reflects the plasma light 8 at each light-emitting point 1a toward a focal point 9 located on the central axis 7; a rotary drive device 48 which rotationally drives the mirror rotating body 40 about the central axis 7; and a cooler 50 which cools the interior of the mirror rotating body 40.

Description

  The present invention relates to a plasma light source system 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 irradiating a resist material by reducing and projecting light or a beam 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 ultra violet (EUV) light source, which means light in a wavelength region of about 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 if a lithography technique combining light of this wavelength and the reflector is developed, it is expected that a processing dimension of 30 nm or less can be realized. 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. DPP has the advantage that the input power is directly converted into plasma energy, so that it has an advantage in conversion efficiency compared to LPP, and the apparatus is small in size and low in cost.

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

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

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)

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 high output is one of the major issues.

Currently, plasma light sources for EUV radiation are being developed in the direction of using high repetition pulse light sources.
However, at high repetition operation (10 to 100 kHz) aiming at practical output, even if energy conversion efficiency (for example, 10% or more) far exceeding the conventional technology is achieved, 1 kW output required for a lithography light source is achieved. In this case, it is necessary to supply power of 10 kW or more to the light source unit.

  On the other hand, when the input energy is increased to increase the output, there is a problem that damage due to a thermal load causes a decrease in the lifetime of the plasma generation apparatus and the optical system.

  The present invention has been developed to solve such problems. That is, an object of the present invention is to provide a plasma light source system that can extend the life of the apparatus by suppressing damage due to thermal load even when the output of the generated plasma light is significantly increased.

According to the present invention, a plurality of plasma light sources that periodically emit plasma light at a plurality of light emitting points installed on a circumference centered on the central axis in a vacuum chamber in which the inside is evacuated,
A mirror rotator that reflects the plasma light at each of the light emitting points toward a condensing point located on the central axis;
A rotational drive device for rotationally driving the mirror rotator about the central axis;
And a cooling device for cooling the inside of the mirror rotating body.

According to an embodiment of the present invention, the mirror rotating body reflects the plasma light at each light emitting point toward a condensing point located on the central axis, and
A mirror support that hermetically surrounds the back of the reflecting mirror;
A hollow rotating shaft having one end fixed to the mirror support and extending along the central axis, the other end positioned outside the vacuum chamber, and having a hollow hole communicating from the inside of the mirror support to the other end .

The cooling device includes a hollow cooling water conduit that communicates from the outside of the hollow rotating shaft to the inside of the mirror support through the hollow hole without contacting the inner surface of the hollow hole;
A cooling water supply device that injects cooling water through the cooling water conduit toward the back of the reflecting mirror and collects the cooling water from a gap between the hollow hole and the cooling water conduit;

Further, the vacuum chamber has a through support portion through which the hollow rotating shaft passes,
A plurality of magnetic fluid seals positioned in the through-supporting portion at an interval in the axial direction of the hollow rotary shaft and hermetically sealing the hollow rotary shaft;
An evacuation device for evacuating the space between the magnetic fluid seals.

  Moreover, it has a balance weight which is fixed to the hollow rotating shaft and adjusts the rotation balance around the central axis of the mirror rotating body.

  Further, it is preferable that the balance weight has a weight that balances with a rotational moment of the mirror rotating body centering on a support position of the rotation driving device.

  According to the configuration of the present invention described above, since the cooling device that cools the inside of the mirror rotating body that reflects the plasma light is provided, even when the output of the plasma light is greatly increased, the damage to the mirror rotating body due to the thermal load is suppressed. The device life can be extended.

  The mirror rotating body includes a reflecting mirror, a mirror support, and a hollow rotating shaft, and the cooling device directly cools the back surface of the reflecting mirror with cooling water through the hollow hole of the hollow rotating shaft. Even when the reflectance is low and the heat load is large, the reflecting mirror can be efficiently cooled to prevent the damage.

In particular, the cooling device includes a hollow cooling water conduit and a cooling water supply device, and the cooling water conduit is not in contact with the inner surface of the hollow hole and is disposed on the back surface of the reflecting mirror via the cooling water conduit. The cooling water is jetted toward and the cooling water is collected from the gap between the hollow hole and the cooling water conduit, so that the rotational resistance is small and the reflection due to the heat load is not affected without affecting the high speed rotation of the mirror rotating body. Mirror damage can be suppressed.

It is embodiment drawing of the plasma light source relevant to this invention. It is operation | movement explanatory drawing of the plasma light source of FIG. 1 is a plan view of a first embodiment of a plasma light source system according to the present invention. FIG. 4 is a side view of FIG. 3. It is a side view of 2nd Embodiment of the plasma light source system 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 a diagram showing an embodiment of a plasma light source related to the present invention. The plasma light source 10 includes a pair of coaxial electrodes 11, a discharge environment holding device 20, and a voltage application device 30.
The pair of coaxial electrodes 11 are arranged opposite to each other with the symmetry plane 1 as the center. Each coaxial electrode 11 includes a rod-shaped center electrode 12, a tubular guide electrode 14, and a ring-shaped insulator 16.

The rod-shaped center electrode 12 is a conductive electrode extending on a single axis ZZ.
The tubular guide electrode 14 surrounds the central electrode 12 with a certain interval, and holds a plasma medium therebetween. The plasma medium is a gas such as Xe, Sn, or Li.
The ring-shaped insulator 16 is a hollow cylindrical electrical insulator positioned between the center electrode 12 and the guide electrode 14 and electrically insulates between the center electrode 12 and the guide electrode 14.

  In the pair of coaxial electrodes 11, the center electrodes 12 are located on the same axis ZZ, and are symmetrically spaced from each other at a constant interval.

  The discharge environment holding device 20 supplies a plasma medium into the coaxial electrode 11 and holds the coaxial electrode 11 at a temperature and pressure suitable for plasma generation. 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.

The voltage application device 30 applies a discharge voltage with the polarity reversed to each coaxial electrode 11. 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 11 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 11 (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 between the pair of coaxial electrodes 11 to contain the plasma in the axial direction.

FIG. 2 is an operation explanatory view of the plasma light source of FIG. 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 will be described with reference to this drawing.

  In the plasma light generation method described above, the pair of coaxial electrodes 11 described above are arranged to face each other, a plasma medium is supplied into the coaxial electrode 11 by the discharge environment holding device 20, and held at a temperature and pressure suitable for plasma generation. Then, the voltage application device 30 applies a discharge voltage with the polarity reversed to each coaxial electrode 11.

As shown in FIG. 2A, a planar discharge current (hereinafter referred to as planar discharge 2) is generated on the surface of the insulator 16 in the pair of coaxial electrodes 11 by applying this voltage. The planar discharge 2 is a planar discharge current that spreads two-dimensionally, and is hereinafter referred to as a “current sheet”.
At this time, the center electrode 12 of the left coaxial electrode 11 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 11 is applied with a negative voltage (−). The guide electrode 14 is applied to a positive voltage (+).

  As shown in FIG. 2 (B), 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. 2 (C), when the sheet discharge 2 reaches the tips of the pair of coaxial electrodes 11, 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 11 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. 2D, the planar discharge 2 is applied to the tubular discharge 4 that discharges between the pair of opposed center electrodes 12 and between the 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 confinement magnetic field (magnetic bin) indicated by reference numeral 5 in the figure is formed, and the plasma 3 can be sealed 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 described above, a pair of coaxial electrodes 11 arranged opposite to each other are provided, and a planar discharge current (planar discharge 2) is generated in each of the pair of coaxial electrodes 11 to thereby generate a planar discharge. 2, a single plasma 3 is formed at the opposite intermediate position of each coaxial electrode 11, and then the planar discharge 2 is switched to a tubular discharge 4 between a pair of coaxial electrodes to contain the plasma 3. Since the magnetic field 5 (magnetic bin 5) is formed, plasma light for EUV radiation can be stably generated for a long time (on the order of μsec).

  In addition, compared with conventional capillary discharge or vacuum photoelectric metal plasma, a single plasma 3 is formed at an intermediate position where a pair of coaxial electrodes 11 face each other, and the energy conversion efficiency is greatly improved (10 times or more). As a result, the thermal load on each electrode during plasma formation is reduced, and the damage caused by the thermal load on the components can be greatly reduced.

  In addition, since the plasma 3 which is a light source of plasma light is formed at an intermediate position where the pair of coaxial electrodes 11 are opposed to each other, the effective radiation solid angle of the generated plasma light can be increased.

However, although the above-described plasma light source can greatly improve the energy conversion efficiency compared with the prior art, the energy conversion efficiency is still low (for example, about 10%) and can be generated for 1 kW of electric power input to the light source unit. The output of the plasma light is only about 0.1 kW.
Therefore, in order to achieve the plasma light output (for example, 1 kW) required for the lithography light source, further ingenuity is required.

FIG. 3 is a plan view of the first embodiment of the plasma light source system according to the present invention, and FIG. 4 is a side view of FIG.
3 and 4, the plasma light source system of the present invention includes a plurality of (in this example, four) plasma light sources 10 (in this example, 10A, 10B, 10C, and 10D) and a mirror rotating body 40.

  Note that the discharge environment holding device 20 and the voltage application device 30 constituting the plasma light source 10 are preferably provided in each of the plurality of plasma light sources 10, but some or all of them may be shared.

The plurality (four) of plasma light sources 10 (10A, 10B, 10C, 10D) periodically emit plasma light 8 at a predetermined light emitting point 1a. The period is preferably 1 kHz or more, the emission time of plasma light is 1 μsec or more, and the output of plasma light is preferably 0.1 kW or more. Moreover, it is preferable that the period, light emission time, and output of each plasma light source 10 are equal.
Moreover, each plasma light source 10 supplies a plasma medium into a pair of coaxial electrodes 11 arranged opposite to each other as shown in FIG. 1, and maintains the temperature and pressure suitable for plasma generation. A discharge environment holding device 20 and a voltage applying device 30 for applying a discharge voltage with the polarity reversed to each coaxial electrode 11 to form a tubular discharge between the pair of coaxial electrodes 11 to generate plasma. It can be contained in the axial direction.

  The mirror rotating body 40 includes a reflecting mirror 42, a mirror support body 44, and a hollow rotating shaft 46.

  In this example, the plurality of light emitting points 1 a of the plasma light source 10 are installed on a circumference around the central axis 7. The intervals on the circumference are preferably set equal to each other. In this example, the central axis 7 is a vertical axis.

The reflection mirror 42 condenses the plasma light 8 at the plurality of light emitting points 1 a of the plasma light source 10 at the condensing point 9.
The reflection mirror 42 is located on the central axis 7, and reflects the plasma light 8 from each light emitting point 1 a of the plasma light source 10 toward the condensing point 9 located on the central axis 7. In this example, the reflection mirror 42 is a concave mirror, but may be a plane mirror.
Further, a condensing mirror (not shown) is provided between the reflecting mirror 42 and the light emitting point 1a, and the plasma light 8 at the light emitting point 1a is condensed on the condensing point 9 by the condensing mirror and the reflecting mirror 42. Good.

The mirror support 44 is a hollow member that hermetically surrounds the back surface (lower surface in the drawing) of the reflection mirror 42 and is hollow inside.
The hollow rotating shaft 46 has one end 46 a (upper end in the figure) fixed to the mirror support 44, extends along the central axis 7, and the other end 46 b (lower end in the figure) outside the vacuum chamber 21 (downward in the figure). A hollow hole 47 is located and communicates from the inside of the mirror support 44 to the other end 46b.

  The vacuum chamber 21 is a constituent member of the discharge environment holding device 20 described above, and hermetically surrounds the plasma light source 10, the reflection mirror 42, and the mirror support 44, and the inside is evacuated.

In FIG. 4, the plasma light source system of the present invention further includes a rotation driving device 48.
The rotation driving device 48 rotates the reflection mirror 42 about the central axis 7 so that the reflection mirror 42 faces the plasma light source when each plasma light source 10 emits light.

  In this example, the rotary drive device 48 includes a bearing mount 48a, a bearing 48b, a gear device 49a, and a drive motor 49b.

The bearing mount 48 a is fixed to the outside of the vacuum chamber 21 (downward in the drawing), has a plurality of bearings 48 b inside, and supports the hollow rotary shaft 46 so as to be rotatable around the central axis 7.
The gear device 49a includes a driven gear fixed to the hollow rotating shaft 46 of the mirror rotating body 49 and a driving gear meshing with the driven gear. The drive motor 49b is an electric motor for high-speed rotation and rotationally drives the drive gear.
In addition, the rotation drive device 48 of the present invention is not limited to this example, and rotation means other than the gear device may be used.

  In this embodiment, the number of plasma light sources 10 is four, but may be two or three or five or more. In particular, in order to shorten the light emission interval and realize high repetition operation (1 to 10 kHz), the larger the number, the more preferable, for example, 10 or more.

  According to the above-described first embodiment of the present invention, a plurality of plasma light sources 10 are installed on the same circumference, and a condensing point 9 by the reflection mirror 42 is formed on the center axis of the circle, and is formed at the center of the circle. The reflecting mirror 42 is arranged to collect light on a vertical axis passing through the center of the circle, and the reflecting surface of the reflecting mirror 42 is synchronized with the light emission timing of each plasma light source 10 arranged on the circumference. By rotating the plasma light source 10 so as to face the plasma light source 10, it is possible to periodically emit a high-power and minute-size plasma light from the condensing point 9.

  Further, although the EUV region mirror has a low reflectance (for example, around 70%), in the configuration of FIG. 3, the plasma light 8 is condensed on the condensing point 9 by one reflection by the single reflecting mirror 42. The reflection efficiency can be increased and the utilization efficiency of the generated EUV light can be increased.

  In FIG. 4, the plasma light source system of the present invention further includes a cooling device 50. In this example, the cooling device 50 includes a hollow cooling water conduit 52 and a cooling water supply device 54.

  In this example, the hollow cooling water conduit 52 is a vertical hollow tube whose lower end 52b is fixed to the outside of the vacuum chamber 21 (in this example, the cooling water supply device 54). The upper end 52 a is communicated from the outside of the hollow rotating shaft 46 to the inside of the mirror support 42 through the hollow hole 47 without contacting the inner surface, and the upper end 52 a is positioned in the vicinity of the back surface of the reflecting mirror 42.

  The cooling water supply device 54 includes a cooling water recovery tank 55 and a cooling water pump (not shown). The cooling water pump injects cooling water from the lower end 52 b of the cooling water conduit 52 toward the back surface of the reflection mirror 42 via the cooling water conduit 52. Further, the cooling water recovery tank 55 is configured to recover the cooling water from the gap between the hollow hole 47 of the hollow rotary shaft 46 and the cooling water conduit 52.

Due to the configuration of the cooling device 50 described above, the mirror in the EUV region has a low reflectance (for example, around 70%), and the amount of heat absorption of the mirror increases accordingly. 50 (the cooling water conduit 52 and the cooling water supply device 54) are not in contact at all, so that a high-speed rotation sealing device (for example, an oil seal) is unnecessary, and the rotational resistance caused by the cooling device 50 can be reduced.
Further, since the cooling device 50 directly cools the back surface of the reflecting mirror 42 with the cooling water through the hollow hole 47 of the hollow rotating shaft 46, even when the reflectance of the reflecting mirror 42 is low and the heat load is large, it is efficiently The reflection mirror 42 can be cooled to prevent the damage.

In FIG. 4, the plasma light source system of the present invention further includes a penetration support portion 62, a plurality of magnetic fluid seals 64, and a vacuum exhaust device 66.
The penetration support part 62 is hermetically fixed to the outer surface of the vacuum chamber 21 and has a through hole 62 a through which the hollow rotary shaft 46 passes.

A plurality (two in this example) of magnetic fluid seals 64 are located between the through hole 62 a of the through support portion 62 and the hollow rotary shaft 46 with a space in the axial direction of the hollow rotary shaft 46. Seal the outer surface of the airtight.
The magnetic fluid seal uses the force that magnetic fluid reacts to a magnetic field, and uses a ring-shaped magnet in combination with a magnetic circuit component sandwiched between ferromagnetic materials such as stainless steel. It is formed on the shaft 46 and prevents dust, oil mist, and the like generated from the drive unit or the like from entering the vacuum chamber 21.

The penetration support part 62 further has a radial hole 62b that communicates the space between the plurality of magnetic fluid seals 64 and the outer surface thereof.
The vacuum exhaust device 66 has an exhaust pipe 65 connected to the radial hole 62 b, and evacuates the space between the magnetic fluid seals 64 through the exhaust pipe 65.

  With the configuration described above, in the present invention, the magnetic fluid seal 64 has a plurality of stages, and the space between the seals is evacuated, so that the amount of leakage can be greatly reduced or eliminated even at high speed.

FIG. 5 is a side view of a second embodiment of the plasma light source system according to the present invention.
In the example of this figure, the central axis 7 is a horizontal axis. The plasma light source system of the present invention further includes a balance weight 68.
In this example, the balance weight 68 is fixed in the vicinity of the other end 46b of the hollow rotary shaft 46, and adjusts the rotational balance around the central axis 7 of the mirror rotating body 40.

In this example, the balance weight 68 has a weight that balances with the rotational moment of the mirror rotating body 40 around the support position of the rotation drive device 48 (for example, the center position of the bearing 48b).
Other configurations are the same as those of the first embodiment.

By providing the balance weight 68 described above, the rotation balance around the central axis 7 of the mirror rotating body 40 can be adjusted, and the mirror rotating body 40 can be rotated at high speed.
The bearing mount 48a of the high-speed rotation mechanism is provided with a balance weight 68 that balances the weight of the reflection mirror 42 and the mirror support 44 on the side opposite to the reflection mirror 42 and the mirror support 44 in vacuum. The rotational moment acting on 48b can be reduced, and the rotating shaft 7 of the mirror rotating body 40 can be held horizontally.

  As described above, according to the configuration of the present invention, the cooling device 50 that cools the inside of the mirror rotating body 40 that reflects the plasma light 8 is provided. Therefore, even when the output of the plasma light 8 is greatly increased, the heat load is increased. It is possible to extend the life of the apparatus by suppressing damage to the mirror rotating body 40.

  The mirror rotating body 40 includes a reflecting mirror 42, a mirror support 44, and a hollow rotating shaft 46. The cooling device 50 cools the back surface of the reflecting mirror 42 with cooling water through a hollow hole 47 of the hollow rotating shaft 46. Since it is directly cooled, even when the reflectance of the reflection mirror 42 is low and the heat load is large, the reflection mirror 42 can be efficiently cooled and its damage can be prevented.

  In particular, the cooling device 50 includes a hollow cooling water conduit 52 and a cooling water supply device 54, and the cooling water conduit 52 does not contact the inner surface of the hollow hole 47 of the hollow rotating shaft 46, and the cooling water conduit The cooling water is jetted toward the back surface of the reflecting mirror 42 through 52 and the cooling water is recovered from the gap between the hollow hole 47 and the cooling water conduit 52, so that the rotational resistance is small and the mirror rotating body rotates at high speed. The reflection mirror can be prevented from being damaged by the heat load without affecting the resistance.

  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, 1a emission point,
2 sheet discharge (current sheet), 3 plasma,
4 Tubular discharge, 5 plasma confinement magnetic field,
6 plasma medium, 7 central axis,
8 plasma light (EUV), 9 focusing point,
10 (10A, 10B, 10C, 10D) plasma light source,
11 Coaxial electrode, 12 Center electrode, 12a Recessed hole,
14 guide electrode, 14a opening,
16 Insulator (porous ceramic),
20 discharge environment holding device, 21 vacuum chamber,
30 voltage application device, 32 positive voltage source,
34 Negative voltage source, 36 Trigger switch,
40 mirror rotating body, 42 reflecting mirror (concave mirror),
44 mirror support, 46 hollow rotating shaft,
46a one end, 46b the other end, 47 hollow hole,
48 rotary drive, 48a bearing mount, 48b bearing,
49a gear device, 49b drive motor,
50 cooling device, 52 cooling water conduit,
52a upper end, 52b lower end,
54 cooling water supply device, 55 cooling water recovery tank,
62 through support, 62a through hole, 62b radial hole,
64 magnetic fluid seal, 65 exhaust pipe,
66 Vacuum exhaust device, 68 Balance weight

Claims (6)

A plurality of plasma light sources that periodically emit plasma light at a plurality of light emitting points installed on a circumference centered on the central axis in a vacuum chamber in which the inside is evacuated;
A mirror rotator that reflects the plasma light at each of the light emitting points toward a condensing point located on the central axis;
A rotational drive device for rotationally driving the mirror rotator about the central axis;
And a cooling device for cooling the inside of the mirror rotating body. The mirror rotator includes a reflecting mirror that reflects the plasma light at each light emitting point toward a condensing point located on the central axis;
A mirror support that hermetically surrounds the back of the reflecting mirror;
A hollow rotating shaft having one end fixed to the mirror support and extending along the central axis, the other end positioned outside the vacuum chamber, and having a hollow hole communicating from the inside of the mirror support to the other end The plasma light source system according to claim 1. The cooling device includes a hollow cooling water conduit that communicates from the outside of the hollow rotating shaft to the inside of the mirror support through the hollow hole without contacting the inner surface of the hollow hole;
A cooling water supply device for injecting cooling water toward the back surface of the reflecting mirror through the cooling water conduit and collecting the cooling water from the gap between the hollow hole and the cooling water conduit. The plasma light source system according to claim 2. The vacuum chamber has a through support part through which the hollow rotating shaft passes,
A plurality of magnetic fluid seals positioned in the through-supporting portion at an interval in the axial direction of the hollow rotary shaft and hermetically sealing the hollow rotary shaft;
The plasma light source system according to claim 2, further comprising an evacuation device that evacuates a space between the magnetic fluid seals.   The plasma light source system according to claim 2, further comprising a balance weight that is fixed to the hollow rotation shaft and adjusts a rotation balance around the central axis of the mirror rotating body.   6. The plasma light source system according to claim 5, wherein the balance weight has a weight that balances a rotational moment of the mirror rotating body centering on a support position of the rotation driving device.