JP2004192914A - Soft x-ray generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft X-ray generator of which the soft X-ray taking out part is not contaminated owing to a sufficient debris removing action as well as which prevents reduction in intensity of an X-ray due to absorption of injection gas for removing debris. <P>SOLUTION: The generator has a mechanism for taking out the soft X-ray irradiated from a plasma generated within a vacuum vessel, removing the debris, generated in generation of the plasma, with injection of a gas flow, and exhausting the gas flow, wherein a Laval nozzle having a rectangular cross section for injecting a supersonic gas flow is disposed as a device for injecting the gas flow, and a vacuum exhausting device for recovering the gas flow to exhaust it is disposed on a downstream side of the gas flow as a device for exhausting the gas flow. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a soft X-ray generator for extracting soft X-rays radiated from high-temperature plasma. More specifically, the present invention relates to a soft X-ray generator which is capable of efficiently removing debris generated during plasma generation. The present invention relates to a soft X-ray generator capable of reliably preventing contamination by debris in a soft X-ray extraction unit by adding a mechanism and minimizing a change in a spatial intensity distribution of soft X-rays. Things. INDUSTRIAL APPLICATION This invention is useful as what provides a soft X-ray generator used as a soft X-ray source, such as a semiconductor lithography apparatus, a biological analysis, and a structural analysis.
[0002]
[Prior art]
Conventionally, a soft X-ray generator has been developed as a device for extracting soft X-rays emitted from high-temperature plasma. In this apparatus, debris is generated when plasma is generated, which causes contamination of the soft X-ray extraction unit. In order to solve the problem of the contamination of the soft X-ray extraction unit due to such debris, for example, a method and an apparatus for removing debris generated during plasma generation by jetting a gas flow have been developed as prior art. However, in this type of method and apparatus, when soft X-rays emitted from the high-temperature plasma pass through the injection gas for debris removal, the absorption of the soft X-rays by the gas occurs, so that soft X-rays are absorbed. There was a problem that the strength of the wire was reduced. In addition, there is a problem that the spatial intensity distribution of the soft X-ray changes before and after the soft X-ray passes through due to the non-uniformity of the density distribution of the jet gas.
[0003]
Here, an outline of a conventional soft X-ray generator having a debris removing mechanism will be described with reference to FIG. In FIG. 2, when a target 15 is irradiated with a laser 15 generated by a laser generator 14, a plasma 8 is generated, and a soft X-ray 17 is generated from the plasma 8. Proceed to section 9. Debris 16 is generated simultaneously with the generation of soft X-rays, and flies toward the X-ray extraction unit 9. Therefore, in order to prevent the soft X-ray extraction unit 9 from being contaminated by the debris 16, the injection gas 19 passes through the high pressure gas supply pipe 2 from the outlet 18 in synchronization with the laser generation by the synchronization signal generator 11. Inject.
[0004]
The debris 16 flying toward the X-ray extraction unit 9 collides with the propellant gas 19, loses its flight speed in the direction of the soft X-ray extraction unit 9, drifts in the vacuum container 10, and then is evacuated from the exhaust device 11 to the vacuum container. It is discharged outside. In the above-described apparatus, for example, when helium gas at about atmospheric pressure is used as the injection gas, the adhesion of debris in the X-ray extraction unit 9 is suppressed to about 1/1000 as compared with the case where there is no injection gas. (See Non-Patent Document 1).
[0005]
[Non-patent document 1]
Laser Research, The Laser Society of Japan, Vol. 27, No. 1, Page 5 (1999)
[0006]
However, in the above-described method, the injection gas 19 diffuses into the space between the plasma 8 and the soft X-ray extraction unit 9 and the soft X-ray extraction There is a problem that the intensity of the soft X-ray 17 in the portion 9 is reduced. In order to reduce the absorption loss of the soft X-rays, for example, if the amount of the gas to be injected is reduced, the debris removing action becomes insufficient, and it is ensured that the soft X-ray extraction unit 9 is contaminated by the debris. There was a problem that it could not be prevented.
[0007]
Further, when the generated soft X-rays 17 pass through the propellant gas 19 and the density distribution of the propellant gas 19 is not uniform, before and after the soft X-rays 17 pass through the propellant gas, the soft X-rays 17 pass through. , The intensity distribution of the soft X-rays obtained by the soft X-ray extraction unit 9 cannot be controlled. From these facts, in the technical field, in the above soft X-ray generator, contamination of the soft X-ray extraction portion due to debris generated during plasma generation is reliably prevented, and soft X-rays generated by a jet gas for removing debris are removed. There has been a demand for the development of a new soft X-ray generating means and device capable of suppressing the absorption loss of the X-ray and preventing the change of the spatial intensity distribution of the soft X-ray.
[0008]
[Problems to be solved by the invention]
Under these circumstances, the present inventors have developed a new soft X-ray generating means and apparatus capable of drastically solving the problems of the above-mentioned conventional technology in view of the above-mentioned conventional technology. As a result of diligent research and investigation as a target, the present inventors have found that the intended purpose can be achieved by using a supersonic gas flow injected from a Laval nozzle having a rectangular cross section as a gas flow. Was completed.
That is, the present invention exerts a sufficient debris removing effect while preventing the soft X-ray intensity loss due to the absorption loss of the soft X-ray due to the injection gas for debris removal, and contaminates the soft X-ray extraction portion due to the debris. It is an object of the present invention to provide a soft X cotton generating device capable of surely preventing the occurrence of the soft X cotton.
Another object of the present invention is to provide a soft X-ray generator in which the spatial intensity distribution of soft X-rays does not change before and after the soft X-rays penetrate the jet gas flow for debris removal. .
Further, the present invention provides a supersonic gas flow which enables a gas flow to be injected into a space between the plasma and the soft X-ray part extraction portion in a controlled form so as not to diffuse into the space. It is an object to provide a jetting means and a device comprising said means.
[0009]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems is: (1) a soft X-ray generator for extracting soft X-rays radiated from plasma generated in a vacuum vessel, wherein debris generated during plasma generation is converted into a gas flow. In a device provided with a debris removal mechanism for removing by injection and a gas flow exhaust mechanism for exhausting a gas flow, a Laval nozzle having a rectangular cross section for injecting a supersonic gas flow is provided at a predetermined position as a device for injecting the gas flow. A soft X-ray generator, wherein a vacuum exhaust device that collects and exhausts a gas flow is disposed downstream of the gas flow as a device that is disposed and discharges the gas flow.
In a preferred embodiment of the present invention, (2) the soft X-ray generator described above, wherein the Laval nozzle is a rapid expansion nozzle (two-dimensional Laval nozzle).
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail.
The present invention includes a mechanism for extracting soft X-rays emitted from plasma generated in a vacuum vessel, removing debris generated during plasma generation by jetting a gas flow, and exhausting the gas flow. A soft X-ray generator, in which a Laval nozzle having a rectangular cross section for injecting a supersonic gas stream is disposed as a device for injecting the gas flow, and a gas flow is exhausted as a device for exhausting the gas flow. A vacuum evacuation device for collecting and evacuating is disposed downstream of the gas flow. In the present invention, it is important to use a Laval nozzle (taper divergent) having a rectangular cross section as a device for injecting the gas flow, and to use a supersonic gas flow as the gas flow.
[0011]
By injecting the supersonic gas flow from the Laval nozzle having the rectangular cross section, the supersonic gas flow is controlled and injected in a predetermined form (sheet shape, curtain shape, etc.). The Laval nozzle needs to have a rectangular cross-section, but any rectangular or rectangular shape may be used as long as it is rectangular. In the present invention, their specific configuration, overall shape, structure, size, etc. can be arbitrarily designed, and all that are recognized as having a substantially rectangular cross-section are included in the scope of the present invention. The present invention, by making the cross-sectional shape of the Laval nozzle rectangular, it is possible to control the form of the supersonic gas flow to be injected, for example, sheet-like, curtain-like, etc., the present invention, These points have the greatest features. Further, the supersonic gas flow is higher than the sonic speed, and the higher the injection speed, the more preferable. As a type of the gas, an inert gas such as helium, argon, and krypton can be used.
[0012]
In the apparatus of the present invention, as described above, in the soft X-ray generator, a Laval nozzle having a rectangular cross section for injecting the supersonic gas flow is arranged, and vacuum exhaust for collecting and exhausting the injected gas flow. The device is arranged downstream of the gas flow, but the position and direction of disposing them in the vacuum vessel are not particularly limited, and may be arbitrarily arranged according to the size and type of the device. Can be. In the apparatus of the present invention, in addition to the debris removing mechanism including the above-described means and the apparatus, as basic components, for example, a vacuum vessel, a high-pressure gas supply means for supplying a high-pressure gas, and a flow rate control means for a high-pressure gas flow , A laser generating means, a laser controlling means, a plasma of a soft X-ray generating source, a target holding means, a soft X-ray extracting section, a vacuum exhausting means, etc., are arranged. , Can be similarly used without being limited to the type.
[0013]
Next, the operation of the device of the present invention will be described. When soft X-rays are generated from high-temperature plasma in a vacuum vessel, debris is generated. In order to prevent the debris from contaminating the soft X-ray extraction unit, for example, a supersonic gas flow is injected through the Laval nozzle in synchronization with a laser. In this case, by injecting the supersonic gas flow from a Laval nozzle having a rectangular cross section, the supersonic gas flow is injected in a sheet shape, for example. The debris that travels in the direction of the soft X-ray extraction unit collides with the sheet-like supersonic gas flow, loses its speed, and together with the supersonic gas flow, a vacuum exhaust for gas flow recovery disposed downstream of the gas flow. It is discharged out of the vacuum vessel through the device.
[0014]
In the present invention, the gas flow for debris removal is controlled and injected in a predetermined form by the specific cross-sectional shape of the Laval nozzle that injects the gas flow, so that the density distribution of the injected gas flow has high uniformity. Have. Therefore, the debris removing action can be sufficiently exerted, thereby reliably preventing the debris of the soft X-ray extraction portion from being contaminated, and before and after the soft X-ray passes through the jet gas flow. A change in the spatial intensity distribution of soft X-rays can be prevented. Further, since the jet gas is jetted into the space between the plasma and the soft X-ray extracting portion in a controlled manner in a predetermined form, the absorption loss of the soft X-ray due to the diffusion of the jet gas is reduced, and thereby the soft gas is softened. X-ray intensity reduction is reduced. Further, in the apparatus of the present invention, as described above, debris removal can be performed with high efficiency, and the form of the apparatus can be easily changed by variously changing the shape and structure of the Laval nozzle. .
[0015]
Furthermore, when a rapid expansion nozzle is used as the Laval nozzle, the influence of the velocity boundary layer on the inner wall of the nozzle can be reduced, a flow that is not affected by shock waves can be easily created, and the nozzle length can be shortened. Becomes possible. In the present invention, the plasma of the soft X-ray generation source of the soft X-ray generation device is not limited to plasma generated using a laser, for example, plasma focus, capillary discharge, gas discharge such as Z pinch discharge, Discharge plasma such as wire discharge can be applied. In the case where a plurality of plasmas of the soft X-ray source are arranged, a plurality of two-dimensional Laval nozzles may be arranged in an arbitrary shape such as a straight line or an arc, depending on the arrangement, and used as a debris removal mechanism. it can.
[0016]
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 shows an example of a soft X-ray generator according to the present invention. In the apparatus shown in FIG. 1, the debris removing mechanism includes a high-pressure gas supply source 1 for supplying a high-pressure gas, a high-pressure gas supply pipe 2, a pulse operation valve 3 for controlling on / off of a high-pressure gas flow, a Laval nozzle 4, and a supersonic gas flow. And a supersonic gas flow recovery vacuum exhaust device 6 which is installed inside the vacuum vessel 10. In the apparatus shown in FIG. 1, when a target 15 is irradiated with a laser 15 generated by a laser generator 14, plasma 8 is generated, and soft X-rays 17 are generated from the plasma 8. Proceed to section 9.
[0017]
In the above apparatus, debris 16 is generated simultaneously with the generation of soft X-rays. In order to prevent the X-ray extraction unit 9 from being contaminated by debris 16, when the pulse operation valve 3 is opened in synchronization with the laser by the synchronization signal generator 12, the high-pressure gas supply source 1 passes through the high-pressure gas supply pipe 2, and A supersonic gas flow 5 is injected through a nozzle 4 into a soft X-ray optical path between a target 7 and a soft X-ray extraction unit 9 through a nozzle 4. At this time, by making the cross-sectional shape of the Laval nozzle rectangular, the supersonic gas flow 5 has a sheet shape. As a result, the debris 16 collides with the sheet-like supersonic gas flow 5, loses its flying speed in the direction of the soft X-ray extraction unit 9, and together with the sheet-like supersonic gas flow 5, the supersonic gas recovery vacuum exhaust device. 6 discharges out of the vacuum vessel 10.
[0018]
As described above, according to this embodiment, the sheet-like supersonic gas flow 5 has directivity, and the supersonic gas recovery vacuum exhaust device 6 is installed downstream of the sheet-like supersonic gas flow 5. Thus, the gas flow is evacuated before the gas diffuses into the vacuum. Thereby, it is possible to exhibit a function as a soft X-ray generator having a debris removing mechanism that exhibits a sufficient debris removing action, while preventing a decrease in the intensity of the soft X-ray 17 due to absorption of the injection gas. Further, by using the Laval nozzle 4, a shock wave is not generated inside the gas flow, the density distribution of the internal space of the sheet-like supersonic gas flow 5 becomes uniform, and before and after the soft X-ray 17 passes through the gas flow. The change in the spatial intensity distribution of the soft X-rays 17 can be minimized.
[0019]
FIG. 3 shows a computer simulation result of the spatial density distribution of gas at the outlet of the two-dimensional Labarnosul 4 in the debris removal mechanism. In this computer simulation, a two-dimensional slit nozzle (rapidly expanding nozzle) having a throat width of 120 microns and an outlet Mach number defined as Mach 5 with respect to helium gas as an operating gas was used as an example. FIG. 4 shows an example in which the cross-sectional configuration of the rapid expansion nozzle is designed. In FIG. 3, the vertical axis (ρ / ρ0) of the graph indicates the gas density standardized by the gas density of the high-pressure gas supply source. The XY spatial coordinate system of the graph is as shown in the upper frame in FIG. The X axis of the graph is the flow direction of the gas flow, and the Y axis is the direction perpendicular to the flow of the gas flow. Thus, it was shown that the gas flow did not spread up to about 5 mm in the downstream direction from the Laval nozzle outlet, and a uniform spatial density distribution was formed.
[0020]
【The invention's effect】
As described in detail above, the present invention relates to a soft X-ray generator having a debris removal function, and according to the present invention, it is possible to 1) jet a supersonic gas flow controlled in a predetermined form. 2) Reduction of soft X-ray intensity due to absorption of the injection gas for removing debris is reduced. 3) Sufficient debris removal action is exhibited to reliably prevent the soft X-ray extraction portion from being contaminated. 4) The spatial intensity distribution of soft X-rays does not change before and after permeation of the jet gas flow for removing debris. 5) A soft X-ray generator having these functions can be provided. 6) Laval nozzle By using a rapid expansion nozzle, the nozzle length can be shortened. 7) This makes it possible to reduce the size of the apparatus.
[Brief description of the drawings]
FIG. 1 shows a cross-sectional view of an example of a soft X-ray generator according to the present invention.
FIG. 2 is a sectional view of a conventional soft X-ray generator.
FIG. 3 shows a simulation result of a spatial density distribution of a sheet-like supersonic gas flow.
FIG. 4 shows a design example of a cross-sectional configuration of a rapid expansion nozzle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 High-pressure gas supply source 2 High-pressure gas supply pipe 3 Pulse operation valve 4 Laval nozzle 5 Supersonic gas flow 6 Vacuum exhaust device for supersonic gas flow recovery 7 Target for soft X-ray generation 8 Plasma of soft X-ray source 9 Soft X-ray Take-out unit 10 Vacuum container 11 Vacuum exhaust device 12 Synchronous signal generator 13 Laser controller for soft X-ray generation 14 Laser device 15 Laser 16 Debris 17 Soft X-ray 18 Blow-out port 19 Injection gas

Claims (2)

A soft X-ray generator for extracting soft X-rays emitted from plasma generated in a vacuum vessel, wherein a debris removal mechanism for removing debris generated during plasma generation by jetting a gas flow, and exhausting the gas flow In an apparatus provided with a gas flow exhaust mechanism,
As a device for injecting the gas flow, a Laval nozzle having a rectangular cross section for injecting a supersonic gas flow is disposed at a predetermined position, and as a device for discharging the gas flow, a vacuum exhaust device for collecting and exhausting the gas flow is provided. A soft X-ray generator arranged downstream of the gas flow. The soft X-ray generator according to claim 1, wherein the Laval nozzle is a rapid expansion nozzle.

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