JP2000091096A - X-ray generator - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Due to metal scattered particles released from LPX,
It can suppress that the optical member is contaminated and the performance is reduced,
Provide an LPX that can be used for a long time. SOLUTION: After the LPX has been operated for a certain period of time, or when the transmittance of the visible light cut X-ray transmission film 107 is monitored and the transmittance becomes lower than a set value, the LPX operation is stopped. Then, the visible light cut X-ray transmission film 107
Is heated to a predetermined temperature, a mixed gas of chlorine gas and SiCl ₄ gas is introduced from a gas inlet 115 and exhausted by a vacuum pump 116 to a predetermined pressure (for example, 0.01 to 0.1 Torr). maintain. Thereafter, the mercury lamp 109 is turned on and the shutter 112 is opened to irradiate the visible light cut X-ray transmitting film 107 with ultraviolet light. As a result, the scattered metal particles adhering to the visible light cut X-ray transmission film 107 become metal chlorides and are discharged out of the vacuum vessel 100 together with the gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray generator suitable for use as an X-ray source for X-ray equipment such as an X-ray microscope, an X-ray analyzer and an X-ray exposure apparatus. The present invention relates to an X-ray generator that can be used for a long time or continuously used by preventing or cleaning an optical system from contamination.

[0002]

2. Description of the Related Art An X-ray source (hereinafter referred to as LPX) utilizing the X-rays radiated from the plasma by converting the material of the target member into plasma by condensing and irradiating a laser beam onto the target member in a reduced-pressure vacuum vessel. Has a brightness comparable to that of an undulator while being small. For this reason, LPX has recently attracted attention as an X-ray source for X-ray equipment such as an X-ray microscope, an X-ray analyzer, and an X-ray exposure apparatus.

[0003] This LPX does not require a high vacuum (about 10 ^-9 Torr) unlike a synchrotron radiation generator. That is, before the laser beam reaches the target member, a vacuum is generated to the extent that it does not receive strong absorption before X-rays generated from plasma are discharged in the air due to residual gas in the vacuum vessel or X-rays generated from plasma reach the irradiation target. Degree is fine. Specifically, the degree of vacuum may be several tens Torr to 0.1 Torr, and the degree of vacuum can be sufficiently achieved by an inexpensive vacuum evacuation device such as a rotary pump.

However, in LPX, in addition to X-rays, ions, atoms or small pieces (hereinafter referred to as scattered particles) are emitted from a target material or peripheral members from plasma or the vicinity of the plasma. These scattered particles are generated by an optical element or the like arranged in the vicinity of the plasma (for example, a window for introducing laser light into the vacuum vessel, a laser light focusing lens arranged in the vacuum vessel, an X-ray radiated from the plasma). Adhering and depositing on reflecting mirrors, filters that transmit X-rays radiated from plasma and cut visible light, etc.), and the performance of these optical elements (reflectance, transmittance, etc.)
Is reduced.

[0005] Replacing optical elements and the like contaminated with scattered particles one by one is not practical because of high cost and labor. In addition, when the optical element or the like is taken out, washed and reinstalled, it is necessary to re-align the optical system each time, which is very troublesome, and this is not practical.

Therefore, in using LPX,
The reduction of the scattered particles is an important issue, and various methods described below have been considered. (1) Fill the gas in the vacuum vessel and reduce or stop the speed of the scattered particles by the collision of the scattered particles with the gas molecules to prevent the scattered particles from reaching the optical element or the like, or reduce the amount of the scattered particles. How to reduce. (2) Dispersion of scattered particles by placing a scattered particle control member that is capable of passing laser light and has an opening large enough to extract radiated X-rays from the generated plasma in the vicinity of the plasma. A method in which the angular distribution is concentrated in the normal direction of the surface of the target member to reduce the amount of X-rays emitted in the direction in which the X-rays are extracted (Japanese Patent Laid-Open No. Hei 6-216131). (3) A method of blocking scattered particles by surrounding the plasma with a scattered particle blocking member that is capable of passing laser light and has an opening large enough to extract radiated X-rays from the generated plasma (JP-A-6-30519
No. 9). (4) A method in which a scattered particle blocking member is arranged so as to be adjacent to or close to a solid angle for extracting X-rays, and an optical element or the like is protected so as to be enclosed therein (Japanese Patent Application Laid-Open No. 7-127600). (5) A method in which a magnet is arranged in the X-ray extraction direction and the trajectory of the scattered particle is bent so that the scattered particle does not reach the X-ray irradiated object (Mochizuki et al., Proceedings of the Japan Society of Applied Physics, 1985).

[0007]

However, when it is intended to reduce the scattered particles simply by filling the gas in the vacuum vessel, the scattered light emitted in a direction different from the direction in which the optical elements and the like are arranged is considered. Particles are also diffused by many collisions with gas molecules, and eventually adhere and deposit on optical elements and the like, and the effect is not sufficient.

In the method described in Japanese Patent Application Laid-Open No. 6-305199, when the solid angle at which the X-ray is taken out increases, the aperture of the scattered particle blocking member increases and the effect is reduced.

In the method described in Japanese Patent Application Laid-Open No. 7-127600, when the solid angle at which the X-ray is taken out becomes large, interference with the excitation laser beam becomes a problem.

When the trajectory of a flying particle is bent using a magnetic field, the speed of the flying particle in a vacuum is very high (> 10 ⁶ cm / sec). In order to bend without hitting, it is necessary to create a large magnetic field, which is difficult to realize. In particular, when the distance from the plasma to the object to be irradiated is reduced in order to obtain a large amount of X-rays, the trajectory of the scattered particles needs to be further bent, and an even larger magnetic field is required. Therefore, it is difficult to manufacture and mount the magnet, and the cost is very high.

The present invention has been made in view of such circumstances, and an optical element, an X-ray optical element, and an optical element arranged in a vacuum vessel by metal scattered particles emitted from LPX are provided.
It is possible to prevent or suppress the deterioration of the performance due to contamination of the optical member, the optical element or the X-ray irradiated object which is the optical member (hereinafter, these are simply referred to as optical elements), and can be used for a long time or continuously. It is an object to provide a simple LPX.

[0012]

A first means for solving the above-mentioned problem is to form a plasma by irradiating a target member in a reduced-pressure vacuum vessel with a laser beam, and to extract X-rays from the plasma. An X-ray generator, wherein at least one of an optical element disposed in the vacuum container or an optical element disposed in the vacuum container or an optical element forming a part of the vacuum container is provided with chlorine gas or An X-ray generator (Claim 1) is provided with a mechanism for introducing at least one of chlorine-containing gases.

In this means, by introducing chlorine or a gas containing chlorine into the vacuum vessel in which the optical element is placed or in the vicinity of the optical element, the scattered particles adhering to the optical element react with chlorine. The scattered particles are removed from the optical element by vaporizing as chloride. This method is particularly effective when the scattered particles are substances that easily react with chlorine, such as when copper is used.

[0014] A second means for solving the above-mentioned problems is as follows.
An X-ray generator for irradiating a target member in a decompressed vacuum vessel with laser light to form plasma and extracting X-rays from the plasma, wherein X-rays radiated from the plasma are generated.
A mechanism is provided for introducing at least one of chlorine gas or gas containing chlorine into a vacuum vessel containing an optical element (first optical element) on which a line is first incident or in the vicinity of the first optical element. An X-ray generator (Claim 2).

Depending on the type of LPX, an optical element (first optical element) on which X-rays radiated from the LPX first enter
However, there is a case where it is installed in a vacuum container different from other optical elements. In this case, since the first optical element is intensively contaminated, it is necessary to prevent performance degradation of the LPX due to contamination of the first optical element. In this means, the same operation as that performed on the optical element in the vacuum vessel or the optical element constituting a part of the vacuum vessel by the first means is performed on the first optical element. Therefore, contamination of the first optical element can be removed.

A third means for solving the above-mentioned problem is as follows.
In the first means, at least one of the optical elements exposed to at least one of the chlorine gas or the gas containing chlorine, visible light, ultraviolet light, vacuum ultraviolet light or shorter wavelength of these An X-ray generator (claim 3), comprising a mechanism for irradiating light.

In this means, Cl radicals are generated when irradiated with ultraviolet light or vacuum ultraviolet light in a chlorine gas (Cl ₂ ) atmosphere. By evaporating the metal scattered particles adhering to the optical element surface as chloride by the Cl radical, the scattered particles on the optical element surface can be removed.
The vaporized metal chloride is exhausted out of the vacuum vessel by a vacuum pump. Therefore, according to the present means, it is possible to prevent or suppress the performance degradation due to the adhesion of the scattered metal particles emitted from the LPX to the optical element and the like arranged in the vacuum vessel, and thus replace the contaminated optical element and the like. There is no need to stop the apparatus for removing or cleaning, and as a result, the apparatus can be operated stably for a long period of time. The gas to be introduced may be only chlorine gas, one kind of gas containing chlorine, or a mixture thereof, or a mixture of two or more gases containing chlorine gas, or a mixture of these and chlorine gas. . For example, a mixed gas of chlorine gas and SiCl ₄ may be used.

A fourth means for solving the above problem is as follows.
An X-ray generator, wherein the second means is provided with a mechanism for irradiating the first optical element with visible light, ultraviolet light, vacuum ultraviolet light, or light having a shorter wavelength. (Claim 4).

Depending on the type of LPX, an optical element (first optical element) on which X-rays radiated from the LPX enter first
However, there is a case where it is installed in a vacuum container different from other optical elements. In this case, since the first optical element is intensively contaminated, it is necessary to prevent performance degradation of the LPX due to contamination of the first optical element. In this means, the same operation as that performed on the optical element in the vacuum vessel or the optical element constituting a part of the vacuum vessel by the third means is performed on the first optical element. Therefore, it is possible to prevent the performance of the LPX from deteriorating due to contamination of the first optical element.

A fifth means for solving the above problems is as follows.
Any of the first to fourth means, further comprising means for heating at least one optical element exposed to chlorine gas or a gas containing chlorine ( Claim 5).

In this means, by heating the optical elements (first optical element when the fourth means is an object) exposed to chlorine gas or a gas containing chlorine, the metal on the surface of these optical elements is heated. The rate of chloride formation increases. Therefore, the speed of removing metal contaminants can be increased.

A sixth means for solving the above problem is as follows.
The optical device according to any one of the first to fifth means, wherein the optical element is made of silicon (Si) or a material containing silicon, or a material whose surface is formed of silicon or a material containing silicon. (Claim 6).

In this means, Cl radicals generated by irradiation of vacuum ultraviolet light in a chlorine atmosphere cause
The silicon surface is etched, and the silicon chloride (SiCl _x ) generated thereby reacts with the metal scattered particles attached to the optical element to generate metal chloride, which is vaporized and discharged out of the vacuum vessel. Especially the third means from the first means
The effect of the means is exhibited.

A seventh means for solving the above-mentioned problems is any one of the third means to the sixth means, wherein visible light, ultraviolet light, vacuum ultraviolet light or light having a shorter wavelength than these is used. Characterized in that the plasma itself for generating X-rays is used as a light source for emitting X-rays.

Light is emitted from LPX over a wide wavelength range from visible light to X-ray. When light in the ultraviolet region to the X-ray region is used, it is not necessary to separately prepare a light source for removing metal contaminants attached to the optical element, so that the configuration of the apparatus becomes very simple. At this time, if the removal rate at which the metal contaminant is removed from the optical element by the light from the LPX exceeds the deposition rate at which the metal scattered particles released from the LPX adhere to the optical element, LP
Even when X is operated, the characteristics of the optical element are not deteriorated due to the adhesion of the metal contaminant, so that the operation can be continuously performed for a long time.

An eighth means for solving the above-mentioned problem is as follows.
In any one of the first means to the seventh means, another halogen gas or a gas containing another halogen gas is used instead of chlorine gas or a gas containing chlorine gas. Item 8). Generally, chlorine gas is preferably used as a gas for reacting with the scattered substance to remove the same, but such effects can be expected with other halogens (for example, fluorine). Therefore, it is possible to select an optimal gas according to the type of the scattered substance.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a first example of an embodiment of the present invention. In FIG. 1, 100 is a vacuum vessel, 101 is a laser beam, 102 is a condenser lens, 1
03 is a laser light introduction window, 104 is a supersonic nozzle, 10
5 is plasma, 106 is X-ray, 107 is visible light cut X
Line transmitting film, 108 is an ultraviolet lamp chamber, 109 is a mercury lamp, 110 is a reflection mirror, 111 is a window, 112 is a shutter, 113 is ultraviolet light, 114 is cluster molecules, 11
5 is a gas inlet, and 116 is a vacuum exhaust device.

From the supersonic nozzle 104, a Kr gas as a target material is jetted by a vacuum pump 116 into a vacuum vessel 100 which has been evacuated in advance by a back pressure of about several to 100 atm. The temperature of the jetted Kr gas rapidly decreases due to adiabatic expansion, and Kr atoms adhere to each other due to van der Waals forces, forming large cluster molecules 114. Laser light 1
By irradiating 01, plasma 105 is generated and X-rays are generated. Since Kr is a gas at room temperature, the scattered particles emitted from the Kr plasma are generated by an optical element (in this embodiment, the visible light cut X-ray transmitting film 10).
Even if it adheres on the laser incident window 7 or the laser incident window 103), it will be vaporized soon, and will not be a factor for deteriorating the performance of the optical element.

However, since Kr adiabatically expands, the Kr cluster number density sharply decreases as the distance from the supersonic nozzle 104 increases. Therefore, when trying to increase the X-ray dose, the supersonic nozzle 104 having a large cluster density is used.
A plasma must be created nearby. Then, the electrons, ions, or atoms emitted from the plasma collide with the supersonic nozzle 104 and members in the vicinity thereof, and scrape these members. The shaved substance turns into scattered particles, and an optical element placed in the periphery (in this example, the visible light cut X-ray transmitting film 1)
07 and the laser incident window 103).

Therefore, when the LPX is operated for a long time, the X-ray transmittance of the visible light cut X-ray transmitting film 107 gradually decreases. When the supersonic nozzle 104 is made of stainless steel, the main metal contaminants adhering on the visible light cut X-ray transmitting film 107 are Fe, Ni, Cr and the like.

The laser beam 101 is condensed by a condenser lens 102 on a target member (Kr cluster molecules in this example) through a laser beam introduction window 103 made of quartz, and a plasma 105 is generated. A part 106 of the X-rays radiated from this plasma is converted into a visible light-cut X-ray transmitting film 107 (here, a 1 μm-thick Si thin film is used).
After passing through, the light is guided to another X-ray optical element (for example, an X-ray multilayer mirror). In the vicinity of the visible light cut X-ray transmission film 107, a heating wire (not shown), which is a mechanism for heating the optical element, is attached.
The line transmitting film 107 can be heated to a temperature of several hundred degrees Celsius. As described above, by heating the visible light cut X-ray transmission film 107 as an optical element, the generation rate of the metal chloride is increased, so that the speed of removing the metal contaminants from the visible light cut X-ray transmission film 107 is increased. .

The ultraviolet lamp chamber 108 contains a mercury lamp 1
09 is attached. UV rays from mercury lamp 1
Reference numeral 13 denotes the window 11 after being reflected by the reflection mirror 110.
After passing through 1 (quartz, CaF ₂ or the like), it is irradiated onto the visible light cut X-ray transmission film 107. These configurations constitute a mechanism for irradiating vacuum ultraviolet light.

In this mechanism, the scattered particles are
A shutter 112 is provided so as not to adhere to or accumulate on the window 1 during the LPX operation.
11 is covered. After the LPX is operated for a certain period of time, or when the transmittance of the visible light cut X-ray transmitting film 107 is monitored and the transmittance becomes lower than a set value, the LPX operation is stopped. Then, the visible light cut X-ray transmission film 107
Is heated to a predetermined temperature (for example, 400 ° C.), a mixed gas of chlorine gas and SiCl ₄ gas (an example of a gas containing chlorine) is introduced from the gas inlet 115, and exhausted by the vacuum pump 116. To maintain a predetermined pressure (for example, 0.01 to several tens of Torr).

After that, the mercury lamp 109 is turned on and the shutter 112 is opened to cut the ultraviolet light into the visible light X.
Irradiation is performed on the line transmitting film 107. Ultraviolet light emitted from the mercury lamp 109 generates Cl radicals. Then, the metal scattered particles adhering to the visible light cut X-ray transmission film 107 react with Cl radicals generated by irradiation of vacuum ultraviolet light in a chlorine atmosphere, or the Si surface by the Cl radicals (visible light X-rays). Silicon chloride (SiCl _x ) generated by etching of the permeable film 107)
Or a reaction with SiCl ₄ introduced into the vacuum vessel to generate metal chloride, which is vaporized and exhausted out of the vacuum vessel 100.

For this reason, the visible light cut X-ray transmitting film 107
The metal contaminants deposited and deposited on the upper surface are removed, and the transmittance of the visible light cut X-ray transmitting film 107 is restored to the original value when the transmitting film 107 is in a clean state. If the above operation is automatically performed during a period in which the X-ray generator is not operating (for example, at night), it is convenient because a clean visible light-cut X-ray transmitting film 107 can always be used when the apparatus is operating. If the X-ray absorption by the chlorine gas or the gas containing chlorine introduced into the vacuum vessel is sufficiently small, the removal may be performed during the operation of the LPX if the removal processing is possible. In this case, the operation of the LPX is not interrupted, which is more effective.

In the embodiment described above, chlorine gas or a gas containing chlorine is introduced into the vacuum vessel,
Although the predetermined pressure is maintained, the gas may be ejected to the vicinity of the optical element by a nozzle or the like. The gas ejection at this time may be continuous or pulsed.

Further, the scattered metal particles may be removed without stopping the operation of the LPX as follows. That is,
If multiple optical elements that perform the same function can be prepared and they can be easily replaced, if the performance of one optical element deteriorates, replace it with another optical element and contaminate the new optical element. Before the performance deteriorates, metal contaminants adhering to the optical element used before are removed by the above-mentioned means.

This method will be described with reference to FIG. In FIG. 2, 201 is a disk, 202a to 202d are visible light cut X-ray permeable films, 203 is a case, 204 and 204 'are openings, 205 is a gas inlet, 206 is a window, 207 is an X-ray source, and 208 is X Wires, 209a to 209d are heating wires, 21
0 is a gas outlet.

As shown in FIG. 2A, one disk 20
Four visible light cut X-ray transparent films 202 of the same material on 1
a to 202d are attached. Heating heating wires 209a to 209d are attached around the visible light cut X-ray transmitting films 202a to 202d. The disk 201 is housed in a case 203 shown in FIG. 2B, and the disk 201 can rotate around its center. The case 203 is provided with openings 204 and 204 ′ opened on the optical axis of the X-ray 208 and a window 206 for irradiating ultraviolet rays (the opening 204 ′ is provided on the back side of the case 203). . The window 206 is provided at a position where scattering particles do not adhere, and an ultraviolet lamp chamber (not shown) is attached in close contact therewith. The case 203 is provided with a gas inlet 205 from which at least one of a chlorine gas and a gas containing chlorine is introduced into the case 203. Further, a gas outlet 210 is attached to the case 203, and an exhaust device (not shown) is provided in front of the gas outlet 210 to exhaust gas introduced into the case 203.

A cylindrical cover is attached to the openings 204 and 204 ′ toward the disk 201, and the tip of the cover reaches the vicinity of the disk 201. Therefore, of the gas introduced into the case 203, the opening 20
4, 204 ′, the amount of leakage into the vacuum vessel in which the case 203 is placed is reduced, and most of the
It is discharged out of the vacuum container from 0. Therefore, Case 2
X-ray absorption by the gas leaked to the outside can be reduced.

Only one of the four visible light cut X-ray transmitting films is disposed at the position of the openings 204 and 204 ′.
During the LPX operation, the scattered particles adhere only to the visible light cut X-ray permeable film at the positions of the openings 204 and 204 ', and the other 3
The scattered particles do not adhere to the two visible light cut X-ray transmitting films. When the transmittance of the visible light cut X-ray transmitting film on the optical axis decreases, the disk 201 is turned so that a new visible light cut X-ray transmitting film is on the optical axis. If the same operation is repeated four times, the first visible light cut X-ray transmission film will return on the X-ray optical axis. On the way, the visible light cut X-ray transmission film contaminated by the scattered particles. Comes to the position of the window 206, a current is applied to one of the corresponding heating wires 209a to 209d to heat it, and at least one of chlorine gas or gas containing chlorine is introduced from the gas inlet 205, and By irradiating ultraviolet light through the filter, the metal scattering particles attached to the visible light-cut X-ray permeable film can be removed by the above-described action, and the transmittance of the visible light-cut X-ray permeable film returned after one round has returned. Has almost recovered to the original transmittance. In this way, the optical performance close to the initial state can always be maintained without interrupting the operation of the LPX.

In the example of FIG. 2, the number of windows for irradiating the ultraviolet rays is one. However, if the number of these windows is increased to three, the time for removing the metal scattered particles becomes longer, so that the metal scattered particles can be more completely removed. Can be removed. As described above, according to the X-ray generator of the present embodiment, it is possible to prevent or suppress performance degradation due to metal contaminants such as an optical element disposed in a vacuum vessel. It is not necessary to stop the apparatus for replacing or removing and washing, and as a result, the apparatus can be operated stably for a long period of time.

In this embodiment, the adhering substance is removed only from the visible light cut X-ray transmitting film.
The process may be performed on the laser light entrance window 103 which is a part of the vacuum container and is an optical member containing Si.

FIG. 3 shows an outline of a second embodiment of the present invention. 3, reference numeral 300 denotes a vacuum vessel, 301 denotes a laser beam, 302 denotes a condenser lens, 303 denotes a laser beam introduction window, 304 denotes a nozzle, 305 denotes a plasma, 306 denotes a multilayer mirror, 307 denotes a heater, and 308 denotes an ultraviolet lamp chamber. , 309 is a mercury lamp, 310 is a window, 311 is a shutter, 312 is a visible light cut X-ray transmission film, 313 is a gas inlet, 314 is a cluster, and 315 is a vacuum exhaust device.

In the embodiment shown in FIG. 3, the target substance and the method for supplying the target substance are the same as in the first embodiment. In the present embodiment, a Mo / Si multilayer mirror 306 designed to have a reflection wavelength peak at a wavelength of 13 nm is used as an X-ray optical element.

X-rays having a wavelength of 13 nm among the X-rays emitted from the plasma 305 are reflected by a parabolic mirror 306 made of a multilayer film of Mo / Si, converted into parallel light, and then cut into a visible light cut X-ray transmission film 312. (0.5 μm thick Si thin film)
It is led to the next stage X-ray optical system. At this time, Mo / Si
The multilayer mirror 306 has a multilayer film formed such that the Si film among the multilayer films of Mo and Si appears on the surface. That is, the surface of the optical element is formed of Si. On the back surface of the mirror, a heater 3 for heating the optical element is provided.
07 is attached so that the mirror 306 can be heated. Here, visible light cut X
The line transmitting film 312 not only cuts visible light but also functions as a pressure partition between the vacuum vessel 300 and the vacuum vessel containing the next stage optical system.

After the LPX has been operated for a certain period of time, or when the X-ray dose transmitted through the visible light cut X-ray transmitting film 312 is monitored and the X-ray dose falls below the set value, LP
Stop the operation of X. Then, the Mo / Si multilayer mirror 30
6 is heated using a heater 307 to reach a predetermined temperature, then a mixed gas of chlorine gas and SiCl ₄ gas is introduced from a gas inlet 313 and exhausted by a vacuum pump 315 to a predetermined pressure (for example, (0.01 to several tens of Torr). Thereafter, the mercury lamp 309 is turned on, the shutter 311 is opened, and ultraviolet light is irradiated onto the multilayer mirror 306. Then, according to the principle already explained, Mo / Si
The metal contaminants attached and deposited on the multilayer mirror are removed, and the reflectivity of the Mo / Si multilayer mirror is restored to its original value.

In this embodiment, a multilayer mirror of Mo / Si is used as the multilayer mirror, but this may be any other multilayer film. For example, Mo / SiC multilayer film or Mo and Si
It may be a Mo / Si / C multilayer film having a C layer for preventing thermal diffusion of Si between the layers. The optical element is not limited to a multilayer mirror, but may be any optical element such as a total reflection mirror such as a Walter mirror or a Kirkpatrick-Bayes mirror or a zone plate. In this embodiment, the metal scattered particles are removed only from the multilayer mirror. However, if necessary, the visible light cut X-ray permeable film 312 may also remove the metal scattered particles.

In this embodiment, the operation of the LPX is stopped when removing the impurities adhering to the X-ray optical element. However, chlorine gas or chlorine-containing gas introduced into the vacuum vessel is used. Even if the absorption of X-rays due to X-rays is sufficiently small, the removal may be performed during the operation of LPX as long as the removal processing is possible. This eliminates the need to stop the operation of the LPX, so that the device can be used efficiently. In the present embodiment, chlorine gas or a gas containing chlorine is introduced into the vacuum vessel to maintain a predetermined pressure. However, the gas may be ejected to the vicinity of the optical element by a nozzle or the like. The gas ejection at this time may be continuous or pulsed.

If the distance between the optical element from which metal contamination is to be removed (the multilayer mirror 306 in this embodiment) and the ultraviolet lamp is large, the ultraviolet light may reach the vicinity of the optical element. And Cl radicals cannot be effectively generated in the vicinity of the optical element. In such a case, the optical element is sealed or roughly covered with a cover provided with a window that transmits ultraviolet light (for example, quartz (SiO ₂ ), MgF ₂ , CaF _2, etc.), and chlorine gas or the like is contained therein. After the pressure in the cover is adjusted to a predetermined pressure by introducing and exhausting, ultraviolet light is irradiated.

This operation will be described with reference to FIG. 4, reference numeral 401 denotes a multilayer mirror; 402, a cover;
3 is a window, 404 is a gas inlet, 405 is an exhaust port, 406
Is an O-ring, and 407 is a heater.

The multilayer mirror 40 is formed by scattering metal particles or the like.
When the reflectance of No. 1 decreases, the operation of the LPX is interrupted, the cover 402 is advanced, and the multilayer mirror 401 is covered by the cover 402 via the O-ring 406. Then, after heating the multilayer mirror 401 to a predetermined temperature by the heater 407, at least one of chlorine gas or gas containing chlorine is covered 402 from the gas inlet 404.
While being exhausted from the exhaust port 405,
02 so that the internal pressure becomes predetermined. afterwards,
Ultraviolet light from an ultraviolet lamp is applied to the multilayer mirror through the window 403. Then, the metal scattered particles are converted into chlorides and vaporized by the effect described above, and are exhausted by the exhaust device, so that the reflectance of the multilayer mirror 401 is restored to the initial value.

The cover 402 may completely or completely seal the multilayer mirror 401. If the sealing is performed roughly, there is not much gas leakage from the cover into the vacuum vessel, so that the pressure in the vacuum vessel can be kept low. With such a method, even when the ultraviolet light source is far away, the ultraviolet light can reach the vicinity of the optical element with little attenuation, and Cl radicals can be efficiently generated near the mirror.

In this embodiment, the optical element is placed in the vacuum vessel for generating LPX, but the X-ray radiated from LPX is
When the optical element (first optical element) on which the line is first incident is installed in another vacuum vessel, at least one of chlorine gas or chlorine-containing gas is supplied to the vacuum containing the first optical element. What is necessary is just to introduce in a container. Further, in the present embodiment, a mercury lamp is used as an ultraviolet light source, but is not particularly limited to a mercury lamp as long as the light source emits light having a wavelength having photon energy capable of generating Cl radicals. For example, excimer laser (ArF, Kr
F) or an excimer lamp.

Since light is emitted from LPX over a wide wavelength range from visible light to X-ray, light from the ultraviolet to X-ray range emitted from LPX may be used as the light source. If light emitted from the LPX is used, it is not necessary to separately prepare a light source for removing metal contaminants attached to the optical element. If light emitted from the LPX is used, it is only necessary to operate the LPX in a chlorine atmosphere around the optical element, so that the configuration of the apparatus becomes very simple. At this time, if the removal rate at which the metal contaminant is removed from the optical element by the light from the LPX exceeds the deposition rate at which the metal scattered particles released from the LPX adhere to the optical element, even if the LPX is operated. Since the characteristics of the optical element do not deteriorate due to the adhesion of metal contaminants, the operation can be continued for a long time.

If the temperature of the mirror rises to a predetermined temperature due to absorption of X-rays by the multilayer film, a heater for heating the multilayer mirror can be omitted. In each of the above embodiments, the cluster material of Kr was used as the target material. However, the present invention is not limited to this.
Any gas cluster such as O ₂ and N ₂ may be used. The form of the target material is not limited to a cluster, and may be a solid, liquid, or gas, and the target material may be any substance.

Further, in the above-described embodiment, chlorine or a gas containing chlorine is used as the introduction gas, but this may be another halogen gas (for example, fluorine) or a gas containing another halogen gas. Good.

[0058]

As described above, in the present invention according to the first and second aspects of the present invention, the optical element disposed in the vacuum vessel or the vacuum vessel or the optical element disposed in the vacuum vessel. Since a mechanism for introducing at least one of chlorine gas or gas containing chlorine is provided in the vicinity of the optical element forming part (or the first optical element), the substance constituting the scattered particles reacts with chlorine. By vaporizing,
The flying substances can be removed from the optical element.

According to the third and fourth aspects of the present invention, in addition to this, at least one of the optical elements (or the first optical element) is provided with a visible light, an ultraviolet light, a vacuum ultraviolet light or a wavelength shorter than these. Since a mechanism for irradiating the optical element is provided, Cl ₂ that comes into contact with these optical elements becomes Cl radicals, and the Cl radicals vaporize metal scattered particles adhering to the optical element surface as chlorides. Scattered particles on the surface of the optical element can be removed. Therefore, there is no need to stop the apparatus to replace or remove contaminated optical elements or the like for cleaning, and as a result,
The device can be operated stably for a long period of time.

According to the fifth aspect of the present invention, since the means for heating the optical element is provided, the generation rate of metal chloride on the surface of the optical element increases. Therefore, the speed of removing metal contaminants can be increased.

In the invention according to claim 6, the optical element is made of silicon (Si) or a substance containing silicon, or is made of a substance whose surface is formed of silicon or a substance containing silicon. The silicon surface is etched, and the silicon chloride (SiCl _x ) generated thereby reacts with the scattered metal particles attached to the optical element to generate metal chloride, so that the metal contaminant removing action is performed particularly efficiently. .

According to the seventh aspect of the present invention, the plasma itself for generating X-rays is used as a light source for emitting visible light, ultraviolet light, vacuum ultraviolet light or light having a shorter wavelength than these, so Since there is no need to separately prepare a light source for removing metal contaminants attached to the apparatus, the configuration of the apparatus is greatly simplified. At this time, if the removal rate at which the metal contaminant is removed from the optical element by the light from the LPX exceeds the deposition rate at which the metal scattered particles released from the LPX adhere to the optical element, the LPX is operated. However, the characteristics of the optical element are not deteriorated due to the adhesion of the metal contaminant, so that the operation can be continued for a long time.

In the invention according to the eighth aspect, since a halogen gas other than chlorine or a gas containing a halogen gas other than chlorine is used as the introduced gas, a gas capable of removing flying substances most quickly is selected and used. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first example of an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an example of an exchange mechanism of a plurality of optical systems.

FIG. 3 is a schematic diagram showing a second example of the embodiment of the present invention.

FIG. 4 is a schematic configuration diagram in which a chlorine gas and / or a gas containing chlorine is introduced into the vicinity of an optical element in a second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 100 vacuum container, 101 laser light, 102 condensing lens, 103 laser light introduction window, 104 supersonic nozzle, 105 plasma, 106 X-ray, 107 visible light-cut X-ray transparent film, 108 UV lamp room, 109
... mercury lamp, 110 ... reflection mirror, 111 ... window, 11
Reference numeral 2: shutter, 113: ultraviolet ray, 114: cluster molecule, 115: gas inlet, 116: vacuum exhaust device, 2
01 ... Disc, 202a-202d ... Visible light cut X-ray transmitting film, 203 ... Case, 204, 204 '... Opening, 20
5 gas inlet, 206 window, 207 X-ray source, 208
.. X-ray, 209a to 209d, heating wire, 210, gas outlet, 300, vacuum vessel, 301, laser beam, 302
... Condenser lens, 303 ... Laser light introduction window, 304 ... Nozzle, 305 ... Plasma, 306 ... Multilayer mirror, 30
7 Heater, 308 UV lamp chamber, 309 Mercury lamp, 310 Window, 311 Shutter, 312 Visible light cut X-ray transparent film, 313 Gas inlet, 314
Cluster, 315: vacuum exhaust device, 401: multilayer mirror, 402: cover, 403: window, 404: gas inlet, 405: exhaust port, 406: O-ring, 407: heater

Claims (8)

[Claims] 1. An X-ray generator for irradiating a target member in a decompressed vacuum vessel with a laser beam to form plasma and extracting X-rays from the plasma, wherein the X-ray generator is in the vacuum vessel or the vacuum vessel. A mechanism for introducing at least one of chlorine gas or chlorine-containing gas is provided in the vicinity of at least one of the optical element disposed therein or the optical element forming a part of the vacuum vessel. X-ray generator. 2. An X-ray generator for irradiating a laser beam to a target member in a reduced-pressure vacuum vessel to form plasma and extracting X-rays from the plasma, wherein the X-rays radiated from the plasma are generated. X-rays provided with a mechanism for introducing at least one of chlorine gas and chlorine-containing gas into a vacuum vessel containing an optical element (first optical element) to which light is first incident or in the vicinity of the first optical element. Generator. 3. The X-ray generator according to claim 1, wherein at least one of the optical elements exposed to at least one of the chlorine gas or the chlorine-containing gas includes visible light, ultraviolet light, An X-ray generator, comprising: a mechanism for irradiating vacuum ultraviolet light or light having a shorter wavelength than these. 4. The X-ray generator according to claim 2, further comprising a mechanism for irradiating the first optical element with visible light, ultraviolet light, vacuum ultraviolet light, or light having a shorter wavelength than these. An X-ray generator. 5. The method according to claim 1, wherein
Item 8. The X-ray generator according to item 1, further comprising means for heating at least one optical element exposed to chlorine gas or a gas containing chlorine. 6. One of claims 1 to 5
Item 8. The X-ray generator according to item 1, wherein the optical element is made of silicon (Si) or a material containing silicon, or is made of a material whose surface is formed of silicon or a material containing silicon. X-ray generator. 7. One of claims 3 to 6
13. The X-ray generator according to item 1, wherein the plasma is used as a light source that emits the visible light, ultraviolet light, vacuum ultraviolet light, or light having a shorter wavelength. 8. One of claims 1 to 7
An X-ray generator characterized in that another halogen gas or a gas containing another halogen gas is used in place of the chlorine gas or the gas containing chlorine gas in the X-ray generator described in the paragraph.