JP3666055B2 - X-ray generator and X-ray exposure apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an X-ray generator used in an X-ray apparatus such as an X-ray exposure apparatus, an X-ray microscope, and an X-ray analyzer.
[0002]
[Prior art]
When laser light (an example of an excitation energy beam) is focused on and irradiated onto a target member placed in a vacuum container that has been decompressed, the target member is rapidly turned into plasma, and X-rays with very high brightness are radiated from this plasma. (X-ray generation) is known (for example, such an X-ray generation source is called LPX: Laser-Plasma X-ray source).
[0003]
Along with the generation of X-rays, scattered particles such as high-speed electrons and ions are emitted from the plasma, and scattered particles of the member material (for example, gasified material, ionized material, small piece of material, etc.) are emitted from the target member. And scattered in the vacuum container (hereinafter collectively referred to as scattered particles).
Among these scattered particles, those having a relatively large shape are called debris. Such scattered particles (particularly debris) collide with the clean optical surface (for example, the surface of the X-ray optical element) and damage them, or adhere and deposit to reduce or change the function and characteristics. So it was a big problem.
[0004]
In order to solve this problem, in the conventional method, a thin film (hereinafter referred to as a scattering particle blocking thin film or an X-ray film) made of a substance having high X-ray permeability (for example, Be) is provided between the X-ray source and the clean optical surface. A scattering filter is prevented from reaching the clean optical surface by installing and shielding a line extraction filter).
As another method, gas in the scattered particles can be obtained by filling a vacuum vessel with a low atomic number gas (for example, He gas) having a high X-ray transmittance or by forming a gas flow of the gas. They attempted to prevent scattered particles by colliding molecules (see JP-A-63-292553).
[0005]
[Problems to be solved by the invention]
The scattering particle prevention thin film can be prevented from adhering to and depositing on the clean optical surface, but instead, scattering particles adhere to and deposit on the scattering particle prevention thin film. There is a problem that the line transmittance gradually decreases (the used X-ray intensity in the X-ray extraction direction decreases).
[0006]
Further, in a method for preventing scattered particles by filling a vacuum vessel with a low atomic number gas (buffer gas) having a high transmittance for X-rays or by forming a gas flow of the gas, There is a problem that the scattered particles cannot be effectively prevented.
For example, when the target member is tantalum, scattered particles are distributed in the normal direction on the surface of the target member in a sufficiently evacuated (pressure 10 Pa or less) vacuum vessel. When a buffer gas for preventing scattered particles is introduced into the vacuum vessel, the scattered particles are reduced due to scattering by gas molecules in the direction in which many scattered particles are released. Will also scatter in the direction where there was little emission of scattered particles.
[0007]
Therefore, when the buffer gas is used to prevent the scattered particles, the distribution in the emission direction of the scattered particles is made uniform. This indicates that the direction in which the emission of scattered particles is small has a smaller effect of introducing the gas than the direction in which the emission of scattered particles is large, or rather the reverse effect.
The extraction of X-rays is generally performed in a direction in which the emission of scattered particles is small, and the effect of gas introduction is small or rather counterproductive in the X-ray extraction direction in which the emission of scattered particles is small. It is a big problem.
[0008]
In particular, in the case of providing a scattering particle control member that controls the directional distribution of the emission amount of scattered particles in the vicinity of the plasma and reduces the emission amount of the scattering particles in the direction of taking out the X-ray, It is a big problem that the effect of gas introduction is small or rather counterproductive with respect to the extraction direction.
The present invention has been made in view of such problems, and is an X-ray generator that uses a buffer gas to prevent scattered particles, and reduces the adhesion and accumulation of unwanted scattered particles in the X-ray extraction direction. As a result, an object is to provide an X-ray generator that can be used stably for a long time.
[0009]
[Means for Solving the Problems]
Therefore, the present invention provides an “X-ray generator that irradiates an excitation energy beam to a target member in a decompressed vacuum vessel to form plasma and extracts X-rays from the plasma, and the target member and / or the plasma An X-ray generator using a buffer gas for blocking scattered particles emitted from a particle is provided with a scattered particle blocking member adjacent to or close to a solid angle region corresponding to the X-ray extraction range. X-ray generator "is provided.
[0010]
The present invention is also an “X-ray generator that irradiates a target member in a decompressed vacuum vessel with an excitation energy beam to form plasma and extracts X-rays from the plasma, and the target member and / or the plasma An X-ray generator that uses a buffer gas to block scattered particles emitted from the X-ray generator, characterized in that a scattered particle blocking member is provided in a solid angle region corresponding to the X-ray extraction range Equipment ".
[0011]
Further, the present invention provides a “scattering particle control member that controls a directional distribution of the amount of scattered particles emitted from the target member and / or the plasma, and controls the amount of scattered particles emitted in the direction of taking out the X-rays. An X-ray generator characterized by further providing a scattering particle control member for reduction is provided.
[0012]
In addition, the present invention provides an “X-ray generator characterized by further comprising a cooling means for cooling the scattered particle blocking member”.
[0013]
[Action]
An X-ray generator that irradiates a target member in a vacuum container with an excitation energy beam to form plasma and extracts X-rays from the plasma, and the scattered particles emitted from the target member and / or the plasma If an X-ray generator that uses a buffer gas to prevent X-rays is provided with a scattering particle blocking member positioned outside (adjacent or close to) a solid angle region corresponding to a range where X-rays are extracted, or inside, a X-ray As a result, it is possible to reduce inconvenient scattered particle adhesion and deposition (adhesion and deposition on a scattering particle blocking thin film, clean optical surface, etc.), and as a result, the X-ray generator can be used stably for a long time. (Claims 1 and 2).
[0014]
As shown in FIG. 1A, a region (solid angle region corresponding to a range in which X-rays are extracted) 103 within a solid angle in which the opening 102 is viewed from the plasma 101 is considered. FIG. 1B shows a cross section including the plasma and the opening.
In a sufficient vacuum state, the scattered particles move linearly, and the scattered particles 110 and 111 emitted into the solid angle region 103 (105) reach the opening 102 only through the region 103 (105).
[0015]
However, when the buffer gas is introduced into the vacuum vessel, the scattered particles collide with the gas molecules and are scattered. Therefore, the scattered particles initially emitted out of the region 103 (105) may have a region as a result of the scattering. Among the particles 112 that enter the region 103 (105) and scattered particles that have once exited the region 103 (105), there are particles 113 that return to the region 103 (105) again.
[0016]
This indicates that the scattered particles that reach the opening 102 do not always pass through the region 103 (105) from the generation to the arrival until the arrival. On the other hand, the optical path of the X-rays generated from the plasma is a straight line, and the X-ray light reaching the opening 102 is always in the region 103 (105).
Here, for example, as shown in FIG. 2, a case where a member 201 with an opening (an example of a scattering particle blocking member) is provided is considered. The opening of the member is equal to the cut surface of the solid angle region 103 (105).
[0017]
Even if the member 201 is provided, the X-ray reaching the opening 102 is not affected at all, and the amount of the extracted X-ray does not change. On the other hand, among the scattered particles, the particles 112 and 113 trying to enter the region 103 (105) are blocked by the member 201, and therefore reach the opening 102 as compared with the case where the member 201 is not provided. Scattered particles are reduced.
[0018]
The scattered particle blocking member that brings about such an effect may have a shape that can prevent the scattered particles that have come out of the region 103 (105) from entering the region 103 (105) again. However, the present invention is not limited to a plate-like product having a hole.
Strictly speaking, the amount of X-rays to be extracted decreases, but the above-described effect can be obtained even if a scattering particle blocking member is provided in the solid angle region corresponding to the range in which X-rays are extracted. For example, as shown in FIG. 8, a very thin plate is provided along the optical path on the X-ray optical path in the solid angle region.
[0019]
In this way, the target member in the decompressed vacuum vessel is irradiated with an excitation energy beam to form plasma, and X-rays are extracted from the plasma, and is emitted from the target member and / or the plasma. An X-ray generator that uses a buffer gas to block scattered particles is provided with a scattering particle blocking member located outside (adjacent or adjacent to) or inside a solid angle region corresponding to a range where X-rays are extracted. In addition, in the X-ray extraction direction, it is possible to reduce inconvenient scattered particle adhesion and deposition (adhesion and deposition on the scattering particle blocking thin film, clean optical surface, etc.), resulting in stable X-ray generation for a long time. A device can be used (claims 1, 2).
[0020]
Moreover, it is a scattering particle control member which controls the directional distribution of the amount of scattered particles emitted, and when a scattering particle control member for reducing the amount of scattered particles emitted in the direction of extracting X-rays is further provided, This is preferable because the effect of preventing scattered particles is increased. In order to reduce the amount of scattered particles emitted in the X-ray extraction direction by such a scattered particle control member, for example, the following shape portion may be provided on the scattered particle control member.
[0021]
As such a shape portion, for example, a through-hole provided in the scattering particle control member, and a maximum opening diameter having a minimum opening diameter portion of 0.1 to 3 mm and an opening angle with respect to the minimum opening diameter portion of 60 to 140 degrees. A through hole having a portion is preferred.
The minimum aperture diameter portion is adjacent to or close to a condensing portion of the excitation energy beam on the target member, and an angle at which the excitation energy beam enters the condensing portion through the through hole is 0 to 60 degrees. In addition, if the X-ray extraction angle with respect to the light condensing portion is set to 30 to 60 degrees, respectively, inconvenient scattering particles in the extraction direction are deposited and deposited without decreasing the X-ray intensity in the extraction direction. Since it can reduce remarkably, it is preferable.
[0022]
The shape part that reduces the amount of scattered particles released in the direction of taking out X-rays is not limited to the through-hole provided in the scattered particle control member. For example, when the scattered particle control member is constituted by a plurality of members, And a tapered gap formed between at least two members of the plurality of members, wherein the minimum gap portion is 0.1 to 3 mm and the opening angle with respect to the minimum gap portion is 60 to 140 degrees. A tapered gap having a maximum gap may be used.
[0023]
The minimum gap of such a tapered gap is adjacent to or close to the condensing part of the excitation energy beam on the target member, and the angle at which the excitation energy beam enters the condensing part through the tapered gap is determined. Setting the X-ray extraction angle to 0 to 60 degrees and the X-ray extraction angle to 30 to 60 degrees respectively reduces inadvertent scattered particle adhesion and deposition without reducing the X-ray intensity in the extraction direction. This is preferable.
[0024]
As a material used for the scattered particle control member according to the present invention, for example, a material having a high melting point or a high hardness such as tantalum, tungsten, diamond, or ceramic is preferable. This is because the scattered particle control member is arranged at a position very close to the plasma, so that release of the member material due to collision of ions and electrons flying from the plasma with the member surface is prevented. That is, if the member material is released, inadequate adhesion and deposition occur as in the case of the scattered particles, and this is prevented.
[0025]
It is preferable to further provide a cooling means for cooling the scattered particle blocking member because the member easily adsorbs the scattered particles and the blocking effect is increased. Alternatively, it is also preferable to process (for example, matte processing) the surface of the scattering particle blocking member so that the scattering particles are easily adsorbed. EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[0026]
【Example】
FIG. 3 shows a schematic configuration diagram of the X-ray generator of the present embodiment. FIG. 4 is a scattered particle control member that controls the directional distribution of the amount of scattered particles emitted. The tape pressing aperture 401 is an example of a scattered particle control member that reduces the amount of scattered particles emitted in the direction of taking out X-rays. It is an expanded sectional view.
[0027]
The angular distribution of the amount of scattered particles emitted is controlled by the aperture 401 and becomes a distribution concentrated in the normal direction of the tantalum tape surface. FIG. 5 shows the angular distribution of the amount of scattered particles emitted with and without the aperture 401.
YAG laser light (an example of an excitation energy beam) 311 is condensed on the surface of a Ta target (an example of a target member) 303 by a condenser lens 312. The Ta target 303 has a tape shape with a thickness of 15 μm, and when plasma is generated, the reel 304 is driven by driving means (for example, a motor, not shown) so that the laser beam is not condensed at the same position on the tape. The laser focusing position is changed while winding the Ta tape by rotating.
[0028]
The moving speed of the Ta tape is a speed at which it moves more than the diameter of the hole generated in the Ta tape by the generation of the plasma before the laser beam for generating the next plasma is incident.
X-rays radiated (radiated) from the generated plasma pass through the X-ray extraction filter (scattering particle blocking thin film) 321 and reach the X-ray optical system.
[0029]
In this embodiment, as shown in FIG. 3, the scattering particle blocking member 330 includes three plates 331, 332, and 333 having apertures that do not block the optical path of the X-rays incident on the filter 321. The plates are separated from each other by a predetermined distance.
Further, helium is introduced as a buffer gas into the vacuum vessel, and helium is introduced and exhausted so as to keep the pressure constant.
[0030]
Since the Ta target 303 has a very high melting point, the generated scattered particles are of an ion or atomic level. The angular distribution of the amount of scattered particle emission is as shown in FIG. 5. In this embodiment, the X-ray extraction angle is set to 45 ° so that the amount of scattered particle emission in the X-ray extraction direction is reduced.
Since the distance from the plasma to the plate 331 is short, the scattered particles reach the plate 331 with almost no influence of the buffer gas. That is, most of the particles other than the scattered particles that have first jumped in the X-ray extraction direction are blocked by the plate 331.
[0031]
As shown in FIG. 5, the emission of scattered particles is concentrated in the normal direction of the surface of the tantalum tape, but the scattered particles in this direction are also blocked by the plate 331, and therefore reach the filter 321 even if scattered by the buffer gas. Never do.
Further, since the scattered particles that have passed through the apertures of the plate 331 travel while being scattered by the buffer gas, the trajectory is not a straight line and deviates from the initial traveling direction toward the filter 321.
[0032]
For this reason, scattered particles that have passed through the apertures of the plate 331 may not be able to pass through the apertures of the plate 332 or the plate 333. Therefore, the scattered particles that finally reach the filter 321 are considerably reduced from the scattered particles that are first generated in the solid angle region corresponding to the range in which the X-ray is extracted.
The shape of the scattered particle blocking member 330 is not limited to the example of FIG. 3, and may be any shape that can efficiently block scattered particles without blocking the optical path of X-rays emitted in the X-ray extraction direction. .
[0033]
For example, a hollow frustum-shaped scattering particle blocking member 341 as shown in FIG. 6 may be used. Alternatively, when it is difficult to finely position the scattered particle blocking member, as shown in FIG. 7, the scattered particle blocking member 351 may be formed of a single plate. Scattered particles coming in the X-ray extraction direction by scattering can be effectively blocked by the scattered particle blocking member 351.
[0034]
Further, although the X-ray optical path in the solid angle region corresponding to the X-ray extraction range is somewhat blocked, as shown in FIG. 8, scattering of a plurality of very thin plates on the X-ray optical path. It is also effective to install the particle blocking member 811 along the optical path.
In this case, even when the scattered particles do not come out of the solid angle region, if the traveling direction is changed by the buffer gas even a little, the particles are adsorbed by the scattered particle blocking member 811.
[0035]
When the scattered particle blocking member 811 shown in FIG. 8 is used, if critical illumination is performed, uneven illumination occurs. However, when Koehler illumination is performed or only the total amount of X-rays is targeted (for example, an analytical instrument) Etc.), the X-ray dose is reduced only slightly, and there is no problem in practical use.
The scattered particle blocking members 330, 341, 351, and 811 are preferably processed (for example, matted) on the surface so that the scattered particles can be easily adsorbed. Further, it is preferable to further provide a cooling means for cooling the scattered particle blocking members 330, 341, 351, and 811 because the member easily adsorbs the scattered particles and the blocking effect is increased.
[0036]
In addition, the shape of a target member is not limited to tape shape, For example, plate shape and a bulk shape may be sufficient. Further, the material of the target member is not limited to Ta, and may be Al, Sn, Zn, Pb or the like.
[0037]
【The invention's effect】
According to the X-ray generator of the present invention, inadvertent scattered particle adhesion and deposition (adhesion and deposition on a scattering particle blocking thin film, clean optical surface, etc.) can be reduced in the X-ray extraction direction. The X-ray generator can be used stably for a long time.
[Brief description of the drawings]
FIGS. 1A and 1B are a perspective view and a schematic cross-sectional view showing a region (solid angle region corresponding to a range where X-rays are extracted) 103 within a solid angle when an opening 102 is viewed from a plasma 101.
FIG. 2 is a perspective view showing a region (solid angle region corresponding to a range where X-rays are extracted) 105 within a solid angle in which the opening 102 is viewed from the plasma 101 when the scattering particle blocking member 201 is provided (a). ) And a schematic sectional view (b).
FIG. 3 is a schematic configuration diagram of an X-ray generator according to an embodiment.
FIG. 4 is a schematic cross-sectional view of an aperture 401 which is an example of a scattering particle control member.
FIG. 5 is a data diagram showing an angular distribution of the amount of scattered particles.
FIG. 6 is a schematic configuration diagram of an X-ray generator of an embodiment when a hollow frustoconical scattering particle blocking member 341 is used.
FIG. 7 is a schematic configuration diagram of an X-ray generator of an embodiment when a scattering particle blocking member 351 made of one plate is used.
FIG. 8 is a schematic cross-sectional view of a scattering particle blocking member 811 comprising a plurality of very thin plates provided on the X-ray optical path.
[Explanation of main part codes]
101... Plasma 102... Opening 103 and 105... Region through which extracted X-ray passes (solid angle region)
110, 111, 112, 113 ... scattered particle trajectory 201 ... scattered particle blocking member 303 ... target member 304 ... reel 311 ... YAG laser beam (an example of excitation energy beam)
312 ... Condensing lens 321 ... X-ray extraction filter (scattering particle blocking thin film)
330, 341, 351 ... Scattering particle blocking members 331, 332, 333 ... Plates having holes (members constituting the scattering particle blocking member 330)
401: Tape pressing aperture (an example of a scattering particle control member)
801 ... plasma 802 ... X-ray extraction filter (thin film for preventing scattered particles)
811 ... Scattered particle blocking member or higher

Claims (10)

An X-ray generator that irradiates a target member in a vacuum chamber with an excitation energy beam to form plasma and extracts X-rays from the plasma, and uses a buffer gas to prevent scattered particles. In the generator,
The solid particles are arranged outside the solid angle region corresponding to the X-ray extraction range so as to surround the scattering particle blocking thin film or the clean optical surface, and the scattered particles emitted outside the solid angle region are again within the solid angle region. An X-ray generation apparatus comprising a scattering particle blocking member having a shape capable of blocking entry into a tube. An X-ray generator that irradiates a target member in a vacuum chamber with an excitation energy beam to form plasma and extracts X-rays from the plasma, and uses a buffer gas to prevent scattered particles. In the generator,
An X-ray generation apparatus comprising a scattering particle blocking member made of a thin plate disposed along an optical path in a solid angle region corresponding to a range in which the X-ray is extracted. The X-ray generator according to claim 2, wherein the scattering particle blocking member is disposed so as to surround the scattering particle blocking thin film or the clean optical surface. The X-ray generator according to any one of claims 1 to 3 , wherein the surface of the scattering particle blocking member is subjected to processing that easily adsorbs scattering particles. The X-ray generator according to claim 1 , further comprising a cooling unit that cools the scattering particle blocking member. The excitation energy beam has a minimum opening diameter portion of 0.1 to 3 mm adjacent to or close to the condensing portion on the target member, and a maximum opening diameter portion having an opening angle of 60 to 140 degrees with respect to the minimum opening diameter portion. 6. The method according to claim 1 , further comprising: a scattering particle control member that controls a directional distribution of a discharge amount of scattered particles emitted to reduce a discharge amount of the scattered particles in a direction in which the X-ray is extracted. The X-ray generator as described in any one of Claims. A tapered gap formed between at least two members, wherein the tapered gap adjacent to or adjacent to the focused portion of the excitation energy beam on the target member is 0.1 to 3 mm in minimum gap And the maximum gap portion having an opening angle of 60 to 140 degrees with respect to the minimum gap portion, thereby controlling the directional distribution of the emission amount of the emitted scattered particles and releasing the scattered particles in the direction of taking out the X-rays. The X-ray generator according to any one of claims 1 to 5 , further comprising a scattering particle control member for reducing the above. 8. The X-ray generator according to claim 6 , wherein any one of tantalum, tungsten, diamond, and ceramic is used as a material used for the scattered particle control member. The X-ray generator according to claim 1 , wherein any one of tantalum, aluminum, tin, zinc, and lead is used as the target material. An X-ray exposure apparatus using the X-ray generator according to any one of claims 1 to 9 in an optical system using Koehler illumination.

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