JP2002184597A - Laser induced x-ray source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen contamination on a laser entrance window by an evaporated metal in a laser induced X-ray source. SOLUTION: In order to satisfy 2 requirements that an evaporated metal is inhibited to reach a laser entrance window 10 by a shielding part B and that a irradiation site 9 is irradiated with a laser beam a without shielding the laser beam a by the shielding part B, a reflection part (reflecting mirror 4a) for reflecting the incident laser beam is provided, whereby the laser beam a is entered through the laser entrance window 10 to generate X-rays, and contamination of the laser entrance window 10 by an evaporated metal c is lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser-induced X-ray source applicable to a nondestructive inspection device and an analysis device.

[0002]

2. Description of the Related Art An X-ray tube or a plasma X-ray source is generally known as an X-ray source used for an X-ray laser, an X-ray lithography apparatus, an X-ray microscope, an X-ray analysis apparatus and the like. The plasma X-ray source uses X-rays generated by the interaction between highly ionized multiply-charged ions and electrons formed in the plasma, and a laser-induced X-ray source that generates high-density plasma with a laser is known. . In a laser-induced X-ray source, a laser beam focused to a size of about 10 μm by a lens or mirror optical system is collected on a metal surface such as Al, Mo, W, Ta, and Au by pulsed light with a time interval of several ns. It is formed by light irradiation, and can mainly obtain soft X-rays.

Further, in a laser-induced X-ray source, a hard X-ray is generated by increasing the power density of plasma generated by using an ultrashort pulse laser such as a femtosecond.
It is known that hard X-rays are generated by increasing the component of a bright line or applying a high voltage even when a pulse laser having a relatively long irradiation time of about nanoseconds is used. Such a hard X having a wavelength of 1 nm or less
Lines are non-destructive inspection devices such as defect inspection of electronic components such as next-generation LSI chips and inspections of the rotating state of engines and motors, and short-term changes in crystal structure due to thermal changes and stress changes utilizing pulse characteristics. Is suitable for observation.

FIG. 7 is a schematic diagram for explaining an example of the configuration of a conventional laser-induced X-ray source. In FIG. 7, a laser-induced X-ray source 100 has an anode 102 and a cathode 103 arranged in a container 105 so as to face each other, and a laser incident window 110 is provided in an opening formed in the wall surface of the container 105.
An X-ray window 111 is provided in an opening formed on the wall surface of the container 105. In this configuration, the anode 102 and the cathode 103
And a laser beam is irradiated from a laser incident window 110 to an irradiation site 109 such as the anode 102 or the cathode 103, and the emitted laser light is used as a trigger to generate plasma, and electrons emitted from the cathode 103 are emitted. Is caused to collide with the anode 102 to generate X-rays, which are taken out of the container 105 from the X-ray window 111.

[0005]

When X-rays are generated, a large amount of electrons collide with the anode. This electron bombardment heats and evaporates the metal forming the anode. As a result, the metal evaporated in the container will adhere to the inside of the container.
This metal is used not only for the inner wall of the container but also for the laser entrance window 1.
Also adheres to the inner surface of 10. When a metal adheres to the inner surface of the laser incident window 110, the transmittance of the laser light is reduced, which causes a problem that it is difficult to introduce the laser light into the container.

Therefore, in the conventional laser-induced X-ray source, it is necessary to perform maintenance such as disassembling the container to remove the metal adhering to the inner surface of the laser entrance window or replacing the laser entrance window. . Therefore, the maintenance cost increases, and the laser-induced X-ray source must be stopped during the maintenance, so that the operation rate of the laser-induced X-ray source and the measurement device using the laser-induced X-ray source decreases. Will do. Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and reduce contamination of a laser entrance window by a vaporized metal in a laser-induced X-ray source.

[0007]

SUMMARY OF THE INVENTION The laser-induced X of the present invention
The radiation source satisfies two points, that is, the prevention of adhesion of the evaporated metal to the laser entrance window and the irradiation of the laser beam to the irradiated area. According to the present invention, as means for evaporating metal to reach and adhere to the laser incident window, a shielding portion is provided on a line connecting the anode from which the evaporating metal is generated and the laser incident window. In a laser-induced X-ray source that generates X-rays by irradiating a laser beam, since a portion irradiated with the laser beam and an anode that generates X-rays are close to each other, a shielding portion is provided on a line connecting the anode and the laser incident window. Is disposed, the laser light is shielded by the shielding portion and cannot irradiate the irradiated portion.

Therefore, the present invention satisfies the two requirements that the shield prevents the evaporated metal from reaching the laser entrance window and that the shield irradiates the irradiated area without blocking the laser beam. For this purpose, a configuration is adopted in which the incident laser light is reflected. As a result, X-rays are generated by irradiating laser light through the laser entrance window, and contamination of the laser entrance window by the evaporated metal is reduced.

Therefore, the present invention provides a laser-induced X-ray source in which a cathode and an anode are arranged to face each other and a laser beam is used as a trigger to generate X-rays by using a laser beam as a trigger. In this order, they are arranged on a line, and a configuration is provided that includes a light reflecting portion that reflects the laser light incident from the laser incident window toward the irradiation site. The light reflecting portion is arranged at a position where an optical path connecting the laser incident window and the laser light irradiation site is not blocked by the shielding portion.

[0010] Thereby, the laser beam incident from the laser incident window is reflected by the reflecting portion, and irradiates the irradiated portion through an optical path that is not shielded by the shielding portion, and X-rays are emitted from the anode near the irradiated portion. appear. In addition, the evaporated metal generated at this time is scattered in all directions, but there is a shielding part on the line connecting the anode and the laser incident window, and the evaporated metal goes straight and does not go around to the shadow part, so the evaporated metal is It is blocked by this blocking part and does not reach the laser entrance window. Thereby, the laser entrance window can reduce the adhesion of the evaporated metal. At this time, the evaporated metal adheres to the reflecting portion, but this is the same as the vacuum evaporation of the metal. Even if the evaporated metal adheres, the reflection efficiency of the laser light is slightly reduced and the generation of X-rays is caused. Has no effect.

The reflector according to the present invention can be configured in various modes. A first mode is a configuration in which a reflecting mirror is mounted on an inner wall surface of a container of a laser-induced X-ray source, and a second mode is a configuration in which a reflecting mirror is mounted at a predetermined position in a container of a laser-induced X-ray source. The third aspect is a configuration in which the inner wall surface of the container itself is used as a reflection surface, and the fourth aspect is a configuration in which a plurality of reflection portions are provided in the container and the incident laser light is reflected a plurality of times.

Further, the shielding portion of the present invention can be configured in various modes. The first mode is a configuration in which a part of the container is used as a shielding part.For example, by swelling a part of the container outward and providing a laser incident window at a position that is shaded from the anode by the swelling part. Shields the adhesion of evaporated metal. Further, a second aspect is a configuration in which a shielding portion is provided in a container, and a third aspect is a configuration in which a reflecting mirror and a shielding portion are shared.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram for explaining a first embodiment of the laser-induced X-ray source of the present invention. FIG. 1A shows a cross-sectional configuration of the laser-induced X-ray source cut in the longitudinal direction of the container, and FIG. 1B shows a cross-sectional configuration of the laser-induced X-ray source cut in the radial direction of the container. ing.

In the configuration of the laser-induced X-ray source 1 shown in FIG. 1, an anode 2 and a cathode 3 are opposed to each other to form an electrode pair.
An electric field is formed between the electrode pairs by the high voltage applied to the electrodes. The high voltage is applied by connecting a high voltage power supply to the anode 2 and the cathode 3. FIG. 1 shows a configuration in which the negative side of the high voltage power supply is connected or grounded to the cathode 3 and the positive side is connected to the anode 2. The cathode 3 is also used as a container 5 that forms a vacuum chamber, and the surface facing the anode 2 is a flat plate having an opening through which X-rays b pass. In addition, the anode 2 has a tip portion whose part facing the cathode 3 protrudes in a needle shape.

In this configuration, a voltage is applied between the anode 2 and the cathode 3 to irradiate the anode 2 or the cathode 3 with laser light from the laser incident window 10 and the emitted laser light is used as a trigger to generate plasma. The X-ray b is generated by colliding the electrons that have flown out of the cathode 3 with the anode 2, and is extracted from the X-ray window 11 to the outside of the container 5.
It is irradiated to zero.

In the first embodiment, a laser a is radiated from a laser light source (not shown) toward the irradiation site 9, and plasma is generated using the laser light as a trigger. The irradiation site 9 can be the cathode 2 or the anode 3 or the vicinity thereof. The laser light a is applied to the irradiation site 9 through an optical path connecting the lens system 12, the laser entrance window 10, and the reflecting mirror (reflecting portion) 4a.

The reflecting mirror 4a can be formed of a metal plate, and is attached to the inner wall surface 6 of the container 5 at a predetermined angle so as to reflect the incident laser light toward the irradiation site 9. The laser entrance window 10 is attached to the entrance 7. The entrance 7 is formed by bulging a part of the wall of the container 5 outward, and a laser entrance window 10 is attached to the bulge side. A part of each wall surface of the container 5 and the incident part 7 forms a shielding part (B in the figure) between the tip part of the anode 2 and the laser incident window 10. The evaporated metal (c in the figure) discharged from the tip of the anode 2 is in a vacuum state (for example, 1).
In the container 5 of ^0-4 Pa), the container 5 goes straight without wrapping around the shaded portion of the shielding portion, and is shielded by the shielding portion.
Therefore, it is possible to prevent the evaporated metal from adhering to the laser incident window 10.

The shielding portion B also functions as a light shielding portion between the cathode 3 and the laser incident window 10, so that the laser light incident from the laser incident window 10 directly irradiates the irradiation site 9 (for example, the cathode 3). It cannot be irradiated. In the laser-induced X-rays of the present invention, the laser light incident from the laser incident window 10 is reflected once by the reflecting mirror 4a and then irradiates the irradiation site 9.

Next, a second embodiment of the laser-induced X-ray source of the present invention will be described with reference to the schematic diagram of FIG. FIG. 2 shows a cross-sectional configuration of the laser-induced X-ray source cut in the length direction of the container. The second embodiment shown in FIG. 2 is different from the first embodiment in the configuration of the reflection unit 4, and the other configurations are common. Therefore, hereinafter, only the configuration of the reflection unit 4 will be described, and description of other configurations will be omitted.

In the reflecting section 4 of the second embodiment, a reflector 4b having a reflecting surface formed of a metal plate or the like is mounted in a container 5. The reflector 4b can be set at an arbitrary position in the container 5 as long as the position and angle at which the laser light reflected from the laser incident window 10 is reflected and the irradiated portion 9 is irradiated with the reflected light can be set. The irradiation of the laser beam and the shielding of the evaporated metal in the second embodiment are performed in the same manner as in the first embodiment.

Next, a third embodiment of the laser-induced X-ray source of the present invention will be described with reference to the schematic diagram of FIG. FIG. 3A shows a cross-sectional configuration of the laser-induced X-ray source cut in the length direction of the container, and FIG. 3B shows a cross-sectional configuration of the laser-induced X-ray source cut in the radial direction of the container. ing. FIG.
The third aspect shown in FIG. 9 differs from the first aspect in the configuration of the reflection section 4, and the other configurations are common. Therefore, hereinafter, only the configuration of the reflection unit 4 will be described, and description of other configurations will be omitted.

In the reflecting portion 4 of the third embodiment, the inner wall 6 of the container 5 itself is used as the reflecting surface 4c. The reflection surface 4c can be formed by polishing the inner wall surface 6 or depositing a metal on the inner wall surface 6. The reflection surface 4c is formed at any position on the inner wall surface 6 as long as the position and angle at which the laser light reflected from the laser incident window 10 is reflected and the reflected light irradiates the irradiation site 9 can be set. can do. The irradiation of the laser beam and the shielding of the evaporated metal in the third embodiment are performed in the same manner as in the first embodiment.

Next, a fourth embodiment of the laser-induced X-ray source of the present invention will be described with reference to the schematic diagram of FIG. FIG. 4 shows a cross-sectional configuration of the laser-induced X-ray source cut along the length direction of the container. FIG. 4A shows an example of the fourth embodiment, and FIG. 4B shows another example of the fourth embodiment. The fourth embodiment shown in FIGS. 4A and 4B is different from the first embodiment in the configurations of the incident section 7 and the shielding section B, and the other configurations are common. Therefore, in the following, the incident portion 7
Only the configuration of the shielding unit B will be described, and description of other configurations will be omitted.

The incident portion 7 of the fourth embodiment forms an opening in the wall surface of the container 5 without bulging the wall surface of the container 5,
It is configured by attaching a laser incident window 10 to the opening. Therefore, according to this configuration, as in the first embodiment, the wall surface of the container 5 can be swelled and the processing can be omitted. In the fourth embodiment, as in the first embodiment, the container 5
Since the shielding part B cannot be formed by the wall surface or the incident part 7, the shielding body 8 is provided as the shielding part B.
The shielding portion 8 is not limited to a metal plate, and may be any material as long as it is a member that shields evaporated metal. In addition, the shielding unit 8
Is on the line connecting the tip of the anode 2 for generating the evaporated metal and the laser irradiation window 10, the optical path connecting the laser irradiation window 10 and the reflection section 4 (reflection mirror 4 a), and the reflection section 4 (reflection mirror 4 a ) Can be placed at any position as long as it is off the optical path connecting the irradiation site 9.

In addition to the arrangement of the shielding portion 8 in the container 5, a part of the inner wall surface 6 of the container 5 can be made to protrude toward the inside of the container. FIG. 4B shows this configuration example. Thereby, the evaporated metal is shielded by the shielding portion 8, and the laser incident window 10 can be prevented from being attached by the evaporated metal. The irradiation of the laser beam in the fourth embodiment is performed in the same manner as in the first embodiment.

Next, a fifth embodiment of the laser-induced X-ray source of the present invention will be described with reference to the schematic diagram of FIG. FIG. 5 shows a cross-sectional configuration of the laser-induced X-ray source cut in the length direction of the container. The fifth mode shown in FIG. 5 is different from the first mode in the configuration of the reflection unit 4, and the other configurations are common. Therefore, hereinafter, only the configuration of the reflection unit 4 will be described, and description of other configurations will be omitted.

The reflecting section 4 of the fifth embodiment includes a plurality of reflecting mirrors 4.
a1, 4a2, 4a3 (or reflecting surfaces 4c1, 4c)
2, 4c3) and attached to the inner wall surface 6 of the container 5. The laser light incident from the laser incident window 10 is sequentially reflected by the reflecting mirrors 4a1, 4a2, and 4a3,
The finally reflected light irradiates the irradiation site 9. Therefore, when the reflecting mirrors 4a1, 4a2, 4a3 (or the reflecting surfaces 4c1, 4c2, 4c3) are installed, the laser light incident from the laser incident window 10 is sequentially reflected, and the finally reflected reflected light is applied to the irradiation site 9. If the position and angle for irradiating can be set, any position in the container 5 can be set.

The irradiation of the laser beam and the shielding of the evaporated metal in the second embodiment are performed in the same manner as in the first embodiment. Note that the plurality of reflecting mirrors 4a1, 4a2, 4a3
(Or the reflecting surfaces 4c1, 4c2, 4c3)
Not only the structure attached to the inner wall surface 6 but also any position as long as the optical path is formed in the container 5 as in the second embodiment, and the number of the reflecting mirrors is also arbitrary. It can be.

Next, a sixth embodiment of the laser-induced X-ray source of the present invention will be described with reference to the schematic diagram of FIG. FIG. 6 shows a cross-sectional configuration of the laser-induced X-ray source cut along the length direction of the container. The sixth embodiment shown in FIG. 6 is different from the fourth embodiment in the configurations of the reflection unit 4 and the shielding unit B, and the other configurations are common. Therefore, in the following, the reflection unit 4
Only the configuration of the shielding unit B will be described, and description of other configurations will be omitted.

The reflecting section 4 of the sixth embodiment includes a reflecting mirror 4d also serving as a shielding section B, and is configured to be combined with the reflecting mirror 4a (or the reflecting surface 4c). The reflecting mirror 4d is the reflecting mirror 4
a (or the reflecting surface 4c) is irradiated with the laser beam reflected on the irradiation site 9, and the evaporated metal emitted from the tip of the anode 2 is shielded to prevent the evaporated metal from adhering to the laser incident window 4d. .

Since the reflecting mirror 4d also serves as the shielding portion B, it is a member having a function of reflecting laser light and a function of shielding evaporated metal. For example, a metal plate having at least one formed as a reflection surface can be used. The reflecting mirror 4
d is a line connecting the tip of the anode 2 for generating evaporated metal and the laser irradiation window 10, an optical path connecting the laser irradiation window 10 and the reflection unit 4 (reflection mirror 4 a), and a reflection unit 4 (reflection mirror). It can be located at any position on the optical path connecting 4a) and the irradiation site 9.

As a result, the evaporated metal is shielded by the shielding portion 8, the laser incident window 10 can be prevented from being adhered by the evaporated metal, and the irradiated laser beam can be irradiated to the irradiated portion. Irradiation of the laser beam in the sixth embodiment is performed in the same manner as in the fifth embodiment described above.
It is performed by being sequentially reflected by the reflection unit.

According to the laser-induced X-ray source of the present invention, since the laser entrance window is not contaminated by the evaporated metal, the laser entrance window is not cleaned or replaced.
It can withstand long-term use. Further, according to the aspect of the laser-induced X-ray source of the present invention, even if the evaporating metal adheres to the reflecting portion, it hardly affects the reflection efficiency of the laser light. , Can withstand long-term use.

[0034]

As described above, according to the laser-induced X-ray source of the present invention, it is possible to reduce the contamination of the laser entrance window by the evaporated metal.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a first embodiment of a laser-induced X-ray source according to the present invention.

FIG. 2 is a schematic diagram for explaining a second embodiment of the laser-induced X-ray source of the present invention.

FIG. 3 is a schematic diagram for explaining a third embodiment of the laser-induced X-ray source according to the present invention.

FIG. 4 is a schematic diagram for explaining a fourth embodiment of the laser-induced X-ray source according to the present invention.

FIG. 5 is a schematic diagram for explaining a fifth embodiment of the laser-induced X-ray source according to the present invention.

FIG. 6 is a schematic diagram for explaining a sixth embodiment of the laser-induced X-ray source of the present invention.

FIG. 7 is a schematic diagram for explaining a configuration example of a conventional laser-induced X-ray source.

[Explanation of symbols]

1,100: laser-induced X-ray source, 2,102: anode,
3,103 ... cathode, 4 ... reflector, 4a, 4d ... reflector,
4b ... reflector, 4c ... reflective surface, 5,105 ... container, 6 ...
Inner wall surface, 7 incident part, 8 shield, 9,109 irradiation part, 10, 110 laser entrance window, 11, 111 X
Line window, 12: optical system, 20, 120: subject, A: vacuum, B: shielding part, a: laser beam, b: X-ray, c: evaporated metal.

Claims (1)

[Claims] 1. A laser-induced X-ray source in which a cathode and an anode are arranged to face each other, and a laser beam is used as a trigger to generate X-rays. A light reflecting portion that reflects the laser light incident from the incident window toward the irradiation site, and the laser light incident from the laser incident window is reflected by the light reflecting portion, without being blocked by the shielding portion. A laser-induced X-ray source, which irradiates the irradiation site.