JP3419906B2 - X-ray generator - Google Patents

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 for generating multiple interference X-rays by injecting charged particles such as electrons into a multilayer thin film.

[0002]

2. Description of the Related Art As a small powerful X-ray source, a resonance transition synchrotron radiation (resona) generated when an electron beam is incident on a multilayer thin film is used.
nce transition radiation) is attracting attention. 14
The configuration of a conventional X-ray generator of this type is shown in FIG.

Reference numeral 1 denotes an electron accelerator for generating an electron beam 2, and reference numeral 3 denotes a multi-layer thin film target 3 arranged along the traveling path of the electron beam 2.
Generates X-rays 4 when the electron beam 2 is incident thereon.

Further, 5 is a beam dump 5 provided in the traveling path of the electron beam 2 after passing through the multilayer thin film target 3. FIG. 15 shows an example of the structure of the above-mentioned multilayer thin film target 3. FIG.
2B is a front view of the multilayer thin film target 3. FIG.

As shown in the figure, Mylar thin films 7 are attached to thin film fixing rings 7 concentrically arranged on a fixing base 9 and having different diameters. In this case, the fixed base 9
A spacer 8 is interposed between the thin film fixing ring 7 and the thin film fixing ring 7 so that the distance between the mylar thin films 6 becomes a constant value. In addition to Myra, a substance having a low primitive number such as Be that absorbs a small amount of X-rays may be generally used.

[0006]

By the way, when a commercially available thin film is used as the thin film constituting the multi-layer thin film target 3, there is a limitation in the selection of the thickness.
When forming a multilayer film from a plurality of uniform thin films, a spacer 8 interposed between the fixing base 9 and the thin film fixing ring 7.
Since there is a need for a jig for adjusting the intervals, there is a problem that the structure of the multilayer thin film target 3 becomes complicated.

On the other hand, in order to change the energy of the X-ray source, if the energy of the electron beam is constant,
It is necessary to change the film thickness and the thin film interval of the multilayer film target 3.

However, when using ready-made products such as Be (beryllium) and mylar, it is difficult to select an arbitrary film thickness, so that the X-ray energy obtained from the multilayer film target 3 is limited. .

The present invention has been made in view of the above circumstances, and the structure of a multilayer film target is simple, and X-rays having strong energy are generated by selecting arbitrary film thicknesses and film thickness intervals. It is an object of the present invention to provide an X-ray generation device capable of performing the above.

[0010]

Therefore, first, in order to achieve the above object, according to the invention of claim 1, an X-ray generator for injecting an electron beam into a multilayer film target to generate multiple interference X-rays is generated. In the apparatus, the multi-layered film target includes a plurality of thin films such as a silicon wafer in which the film thickness of a thin film part serving as the electron beam passage region is thinner than the film thickness other than the part serving as the passage region. It is characterized in that it is configured by stacking thick portions as spacers.

According to a second aspect of the present invention, in the X-ray generator according to the first aspect, the thin film forming the multilayer film target has a crystalline structure, and the thin film in the incident direction of the electron beam. It is characterized in that the multilayer film target is arranged such that a crystal plane of a thin film portion of the thin film forms a predetermined angle.

Further, according to the invention of claim 3, in the X-ray generator according to claim 1 or 2, at least one of the thin films of the plurality of thin films is exposed to the outside from the thin film part. It is characterized by having two notches.

Further, according to the invention of claim 4, in the X-ray generator for injecting the electron beam to the multilayer film target to generate the multiple interference X-rays, each thin film portion becomes a passing region of the electron beam. Is formed by stacking a plurality of thin films, such as silicon wafers, which are formed to have a thickness smaller than that of a portion other than a portion serving as a passage region, and a portion having a large thickness of the thin films is stacked as a spacer, and a predetermined electron energy A plurality of multi-layered film targets in which the film thicknesses of the thin film parts and the intervals between the thin film parts are determined so that the generated x-rays cause multiple interference. Switching means for switching any one of the plurality of multilayer film targets so as to be arranged on the way of the electron beam traveling.

[0014]

According to the first aspect of the invention, since the multilayer film target is constructed by laminating a plurality of thin films such as a silicon wafer having a thin film portion as spacers having a large film thickness, the structure is simple. An X-ray generator can be provided.

According to the second aspect of the invention, since the multilayer film target is arranged so that the crystal plane of the thin film portion of the thin film forms a predetermined angle with respect to the incident direction of the electron beam, it occurs from the boundary surface of the thin films. It becomes possible to extract the transition radiation X-rays in a relatively large angle direction with respect to the direction of the electron beam.

According to the invention of claim 3, in the X-ray generator according to claim 1 or 2, at least one notch cut out from the thin film portion to the outside in the thick portion of the plurality of thin films. Since the grooves are provided, the gas between the thin films can be quickly exhausted, and as a result, the pressure difference between the thin films can be eliminated and the intervals between the thin films can be made uniform.

According to the fourth aspect of the present invention, one of the plurality of multilayer film targets for generating X-rays of different energies for a predetermined electron energy by the switching means.
By switching to one multilayer film target, it is possible to provide an X-ray generator capable of generating variable-energy X-rays.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 shows the schematic arrangement of an X-ray generator according to the first embodiment of the present invention.

As shown in the figure, a multilayer film target 13 held by a target holder 14 is arranged on the way of the electron beam 12 generated from the electron accelerator 11, and further passes through the multilayer film target 13. A beam dump 16 is provided on the subsequent traveling path of the electron beam 12.

The multilayer film target 13 is shown in FIG.
As shown in (a) and (b), a central portion of a rectangular thin film 21 such as a silicon wafer has a thicker portion 22 on the outer peripheral side and a thicker film 22 through which the electron beam 12 passes on the inner side. A thin thin film portion 23 is formed.

The thickness of the thin film portion 23 is determined by the conditions under which the X-rays due to the transition radiation from the boundary surfaces on both sides interfere with each other.
The multilayer film target 13 is configured by laminating a plurality of thin films 21 with the thick outer peripheral portion being a spacer.

Therefore, the distance between the thin films 21 is set to
It is adjusted by the step between the thick portion 22 on the outer peripheral side and the thin portion 23 on the inner side. This value is determined by the conditions under which transition radiation X-rays between different thin films interfere with each other.

Next, a method of manufacturing the thin film 21 shown in FIG. 2 will be described with reference to FIGS. The thin film 21 is
A silicon (100) wafer that has been mirror-polished on both sides is shaped by anisotropic etching, and then each element is cut out to manufacture.

FIG. 3 shows an explanatory view for explaining the outline of the first thin film forming method. (1) First, a thin film portion is formed on the silicon wafer 31. (2) The wafer 31 is thinned.

(3) Each element 32 (thin film 21) is cut out from the wafer 31. Next, details of the first thin film forming method will be described with reference to FIG. (A) First, the silicon wafer 31 is oxidized to form a silicon oxide film 33.

The silicon oxide film 33 is used as a mask layer in anisotropic etching, and the forming method is not limited to oxidation, and a silicon oxide deposition layer such as CVD may be used. The mask material is not limited to the silicon oxide film. For example, when an aqueous solution of potassium hydroxide is used as an anisotropic etchant, the oxide film may be thickened to deal with it.
Since the potassium hydroxide aqueous solution dissolves the silicon oxide film relatively well, a silicon nitride film which is difficult to dissolve in the potassium hydroxide aqueous solution is often formed. The nitride film may be a metal film.

(B) Next, the silicon oxide film 33 is patterned to form a thin film. (C) The patterned wafer 31 is etched to a predetermined depth with a silicon anisotropic etchant to form a thin film portion.

As this anisotropic etchant, an ethylenediamine / pyrocatechol (EDP) aqueous solution, a potassium hydroxide (KOH) aqueous solution, a tetramethylammonium hydroxide (TMAH) aqueous solution, etc. are known.

(D) The shape-processed wafer 31 is oxidized again after removing the silicon oxide film 33 (this process can be omitted), and the silicon oxide film on the surface opposite to the shape-processed surface is removed. It

(E) This wafer 31 is anisotropically etched to reduce the thickness of the final element. As a characteristic of anisotropic etching, etching progresses uniformly in the direction perpendicular to the (100) plane, and the etched surface becomes very smooth. Therefore, the thin film formed by etching has a uniform thickness and has a very smooth mirror surface.

(F) Next, the oxide film on the thinned wafer 31 is removed. (G) The wafer 31 from which the oxide film is removed is diced to separate each element. Through the above steps, the thin film 32 forming the multilayer film target can be obtained.

The step (f) can be performed after the step (g). In this case, there is an advantage that damage and dirt on the silicon surface during dicing can be reduced, although it is only on the surface with the oxide film.

Next, the outline of the second thin film forming method will be described with reference to FIG. The method of forming the second thin film is as follows: (1) First, the silicon wafer 31 is thinned.

(2) A thin film portion is formed on the silicon wafer 31. (3) Each element is cut out from the wafer 31. It consists of the process.

Next, the details of the second thin film forming method will be described with reference to FIG. (A) First, the silicon wafer 31 is thinned to the final element thickness. In this step, the wafer 31 may be mechanically polished, or the double-sided mirror-polished wafer 31 may be thinned by anisotropic etching.

(B) The thinned wafer 31 is oxidized to form a silicon oxide film. (C) Pattern the thin film portion. (D) Silicon is etched by anisotropic etching to form a thin film.

(E) The oxide film is removed. (F) Finally, dicing is performed to complete the thin film (silicon target element) 32.

This second thin film forming method has an advantage that the number of times of oxidation is one and the number of steps is small as compared with the above-described first thin film forming method. As the element becomes thinner, the risk of the element breaking during the dicing process increases, and the wafer on which the element is formed is easily broken and becomes difficult to handle. This risk can be avoided by separating the elements by etching instead of dicing.

Next, the process of separating elements by etching will be described with reference to FIG. (1) A thin film portion is formed.

(2) The part where the element is separated from the wafer 31 is etched. (3) The substrate is thinned by etching from the opposite side of the wafer 31, and the element portion is separated from the wafer 31.

In this process, since dicing is not performed, there is less risk that the element will be broken. However, since the element is separated by etching, the thin film 41 (silicon target element) is completely etched by etching as shown in FIG. The beam-shaped support portion 42 is formed so as not to be separated, and after etching, it is cut off by a laser or broken off.

Incidentally, FIG. 8A shows a plan view of the thin film 41, and FIG. 8B shows a BB sectional view of the thin film 41.
In the process of separating the elements by etching as described above, the thin film portion was formed by etching from one side, but as shown in FIG. 9, etching processing may be performed from both sides of the thin film 41.

In the above-described first and second thin film forming methods, a plurality of thin films are formed on the wafer, and each element is separated by dicing at the end. However, each thin film is formed at the beginning of the process. After cutting the chip to the size of, the thin film portion is processed, or in the second thin film forming method described above, steps (2) and (3) are reversed, that is, a thin wafer is formed. It is also possible to carry out the processing for thin film formation after cutting into chips of the size of each thin film.

The advantage of adopting such a process is that there is no risk of destruction at the time of element separation. Next, a multilayer film target is manufactured by stacking a plurality of thin films obtained through the above-described process.

A thin film which is a silicon target element is formed by a direct silicon bonding technique (for example, Journal of Applied Physics, Vol.
Volume 3 (1987) pp. 373 to 376). The silicon target element is stacked and fixed on the target holder, but a single element is thin and easily broken, so that the assembly work for stacking and fixing must be performed with great care.

Therefore, if the elements are laminated in advance by using the silicon direct bonding technique to make a laminated target in which the elements are laminated and integrated, the laminated and integrated element has high strength and can be easily attached to the target holder. Makes assembly work easier.

Further, the feature of this technique is that it can be pasted without an adhesive, and has the same size as the case of stacking after pasting. Therefore, even when this method is adopted, there is an advantage that it is not necessary to change the element thickness at the time of manufacturing the element or to adjust the element interval at the time of bonding.

Since the target element having the conventional structure is a combination of elements having different diameters, it is necessary to manufacture the elements having different diameters by the number of combinations. According to the invention of the present embodiment, the target element is formed by stacking thin films having the same structure, so that it is possible to provide a multilayer film target having a simple structure and little sagging of the thin films.

There is also a manufacturing advantage that only one kind of thin film needs to be manufactured. Furthermore, since semiconductor silicon is used, a large amount of thin film can be formed at one time.

Further, the change of the film thickness and the film interval of the thin film 21 can be easily dealt with only by changing the etching amount of silicon, and a highly accurate element can be easily manufactured according to the required specifications. .

Furthermore, since the film thickness and interval of the multilayer film target 13 can be selected to predetermined values, X-rays of arbitrary energy are multiply interfered with predetermined electron energy to generate strong X-rays. It is possible to provide an X-ray generating device. <Second Embodiment> Next, referring to FIG. 10 and FIG.
An X-ray generator according to the second embodiment of the present invention will be described.

FIG. 10 is a view showing the arrangement of the multilayer film targets of the X-ray generator of this embodiment, and FIG. 11A is a plan view of the thin films constituting the multilayer film target of the embodiment.
(B) shows a cross-sectional view of a thin film constituting the multilayer film target of the example. The method of manufacturing this thin film is the same as the method described in the first embodiment.

The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals in the following description. That is, in this embodiment, the multilayer film target 1 fixed to the target holder 14 is
3 is arranged so that the crystal plane of the thin film 13 forms an angle θB with respect to the incident direction of the electron beam 12.

This angle θ B is a Bragg condition with respect to a crystal plane (for example, (011) plane) of a predetermined transition radiation X-ray energy obtained by processing a single crystal (for example, (100) plane of silicon) with a step. Determined by

The transition radiation X-rays radiated from the multilayer film target 13 are arranged at the film thickness and the spacing satisfying the resonance condition of the multiple interference as described above, so that the X-rays emitted at the Bragg condition angle. Also causes multiple interference.

Therefore, by adopting such a structure, in addition to the effect of the first embodiment described above, transition radiation X-rays generated from the boundary surface of the thin film 21 are further directed in the direction of the electron beam 12. On the other hand, it is possible to take out in a relatively large angle direction. <Third Embodiment> Next, an X-ray generator according to a third embodiment of the present invention will be described.

The difference between this embodiment and the above embodiment is that
As shown in FIG. 12, the thin film 21 is included in the multilayer film target 13. The method for manufacturing this thin film is the same as the method described in the first embodiment.

That is, in the present embodiment, the notch groove 51 communicating from the thin film portion to the outside is provided in the thick film portion on the outer peripheral side of the thin film 21. By adopting such a configuration, when the multilayer film target 13 is placed in a vacuum, the communication groove 51 facilitates exhaustion between the thin films 21, and as a result, there is no pressure difference between the thin films 21. Therefore, it is possible to make the intervals of the thin films 21 uniform. <Fourth Embodiment> An X-ray generator according to the fourth embodiment of the present invention will be described with reference to FIG. The same parts as those in FIG. 1 will be described with the same reference numerals.

The difference between the above embodiment and this embodiment is that a target exchanging device having a plurality of multilayer film targets is provided. That is, as shown in FIG. 13, a target exchanging device 61 having a plurality of multilayer film targets 13 fixed on the target holder 14 after being stacked on the target holder 14 is provided along the traveling path of the beam 12.

Each multilayer film target 14 generates X-rays of different energies with respect to a predetermined electron energy, and the film thickness and film interval are determined so that the generated X-rays cause multiple interference.

The target exchanging device 61 has a switching means for switching any one of the plurality of multilayer film targets 13 so as to be arranged on the way of the electron beam 12 traveling. The method for manufacturing this thin film is the same as the method described in the first embodiment.

Therefore, a plurality of multilayer film targets 13 optimized in advance for the required X-ray energy can be used by appropriately switching them by the switching means of the exchanging device 61, so that X-rays with variable energy can be generated. be able to.

[0063]

As described above in detail, according to the X-ray generator of the present invention, the structure of the multilayer film target is simple, and strong energy can be obtained by selecting an arbitrary film thickness and film thickness interval. It is possible to provide an X-ray generator that can generate the X-rays that it has.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an X-ray generator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a structure of a thin film forming the multilayer film target in the first embodiment.

FIG. 3 is an explanatory view for explaining an outline of a first thin film forming method in the first embodiment.

FIG. 4 is an explanatory view illustrating details of a first thin film forming method in the first embodiment.

FIG. 5 is an explanatory view illustrating an outline of a second thin film forming method in the first embodiment.

FIG. 6 is an explanatory view illustrating details of a second thin film forming method in the first embodiment.

FIG. 7 is an explanatory diagram illustrating a process of separating elements by etching in the first embodiment.

FIG. 8 is a plan view and a cross-sectional view of a thin film according to the first embodiment.

FIG. 9 is a cross-sectional view of a thin film etched from both sides in the first embodiment.

FIG. 10 is a diagram showing a configuration of an X-ray generator according to a second embodiment of the present invention.

11A and 11B are a plan view and a cross-sectional view of a thin film forming a multilayer film target according to the second embodiment.

FIG. 12 is a diagram showing a structure of a thin film of an X-ray generator according to a third embodiment of the present invention.

FIG. 13 is a diagram showing a configuration of an X-ray generator according to a fourth embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of a conventional X-ray generator.

FIG. 15 is a diagram showing a configuration of a conventional multilayer thin film target.

[Explanation of symbols]

11 ... Electron accelerator, 12 ... Electron beam, 13 ... Multilayer film target, 14 ... Target holder, 15 ... X-ray, 16
... beam dump, 21 ... thin film, 22 ... thick part of thin film, 23 ... thin film part, 31 ... silicon wafer, 32 ... element, 33 ... oxide film, 41 ... thin film, 42 ... beam-like support part, 5
1 ... Notch groove, 61 ... Target exchange device.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Nakayama 1 Komushi Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba R & D Center Co., Ltd. (72) Inventor Masayuki Sekimura Komukai-shi Toshiba, Kawasaki-shi, Kanagawa No. 1 in Research & Development Center, Toshiba Corp. (56) Reference Japanese Patent Laid-Open Publication No. 50-142185 (JP, A) Hirakai 3-124497 (JP, U) Ryuji Tanaka, et al. Resonance transition by multi-layer thin film, monochromatic emission, NRI Research Report, Japan, June 1993, Vol. 26 / No. 1, 147-153 Ryuji Tanaka et al. Resonance effect of transition radiation emitted from multilayer thin films, NRI Research Report, Japan, December 1993. , Vol. 26 / No. 2, 330 -339 (58) investigated the field (Int.Cl. ^7, DB name) H05G 1/00 - 2/00 JICST file (JOIS) patent file (PATOLI ) Practical file (PATOLIS)

Claims (4)

(57) [Claims] 1. An X-ray generator for generating multiple interference X-rays by injecting an electron beam into a multilayer film target, wherein the multilayer film target has a film thickness of a thin film portion serving as a passage region of the electron beam. An X-ray generator characterized in that a plurality of thin films such as a silicon wafer formed thinner than the portions other than the portions to be formed are laminated by using the thick portions of the thin films as spacers. 2. The thin film forming the multi-layered film target has a crystal structure, and the multi-layered film target is arranged so that a crystal plane of a thin film portion of the thin film forms a predetermined angle with respect to an incident direction of the electron beam. Claim 1 characterized by the above.
The described X-ray generator. 3. The X-ray generator according to claim 1, wherein at least one notch groove that is pulled out from the thin film portion is provided in a thick portion of the plurality of thin films. . 4. An X-ray generator for generating multiple interference X-rays by injecting an electron beam into a multilayer film target, each of which has a film thickness of a thin film part which is a passing region of the electron beam except a part which is a passing region. Is formed by laminating a plurality of thin films such as silicon wafers, which are formed to be thinner than the film thickness, as spacers having thick film thicknesses, and X-rays having different energies for predetermined electron energies are generated. A plurality of multilayer film targets in which the film thickness of the thin film portion and the distance between the thin film portions are determined so that the generated X-rays cause multiple interference, and any one of the plurality of multilayer film targets An X-ray generation device comprising: a switching unit that switches one multilayer film target so as to be disposed on the way of the electron beam.