JPH0377252A - Minute x-ray source - Google Patents

Abstract

PURPOSE:To improve luminance of an x-ray generating part by forming a minute hole which pierces a first electron scattering and thermally diffusing layer and reaches an x-ray generating layer and radiating an electron beam to the hole for exciting the x-ray. CONSTITUTION:Accelerated electrons at several 10keV-100keV concentrated narrow by an objective lens are radiated to an x-ray generating layer 13 which is a bottom part of a pin holes or a V-shaped groove 16 having different depth. A spherical x-ray generating part 9 is thus provided. When electron beam 6 is radiated in a multilayer using a multilayered pin hole or a V-shaped groove 16 having different depth, reflection electrons are closed and do not come out and thus the x-ray generating part 9 becomes spherical and excessive x-ray is generated at a part 17 as compared with a conventional one. As a result, without altering the apparent size of the x-ray generating part 9, the luminance of the x-ray generating part 9 is improved by the luminance intensity at the part 17.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a micro X-ray source for a projection type X-ray microscope, and in particular, despite the small size of the X-ray generating part, First, it concerns a small XLS source with high brightness.

[Conventional technology]

Conventionally, a projection type X-ray microscope is known as a device for obtaining an enlarged transmission X-ray image of a sample. This device is equipped with a minute XwA source 2, as shown in the schematic overall configuration diagram of FIG. Sample 3 is placed and source 2
A detector 5 such as a film, a position-sensitive detector, a fluorescent screen, etc. is arranged to receive and detect the divergent X-rays 7 emitted downward and radially from the sample 3 and transmitted through the sample 3 at a remote position.

A portion consisting of the radiation source 2, sample 3, support mesh or support film 4, and detector 5 is called a camera section 8, and projects an enlarged transmitted X-ray image of the sample 3 onto the detector 5.

The micro X-ray source 2 is constructed by placing a metal foil 21 on which you want to generate X-rays at the focal position of the objective lens 1 of an X-ray microanalyzer, a scanning electron microscope, a scanning image observation device of a transmission electron microscope, etc. An electron beam 6 accelerated from l to several 10 keV to 100 aV is emitted and applied to the metal foil 21 to generate characteristic X-rays. Metal foil 21 and measurement sample 3
In addition to the method of arranging the measurement sample 3 in close proximity to the metal foil 21, there is also a method of evaporating a metal that generates characteristic X-rays directly onto the measurement sample 3 to form the film 21. However, methods have been used in which the film 21 is exposed to electron beams in the same manner as described above to generate X-rays.

[Problem to be solved by the invention]

The operation of the conventional minute X-ray source 2 will be explained using the enlarged view of FIG. The conventional micro X-ray source 2 consists of a single metal foil or membrane 2
1, and when an accelerated electron beam 6 is applied to this surface,
An X-ray generating section 9 having a shape in which the head of a sphere is cut out is formed inside from the surface thereof, and an electron scattering section 10 that generates heat is formed around the X-ray generating section 9 . Such a single metal foil or film 21
In the method of generating X-rays using the X-ray generator, it is necessary to reduce the size of the X-ray generating section 9 and increase its brightness, but it has been difficult to achieve both of these goals. That is, in order to increase the brightness, it is sufficient to increase the number of electron beams per unit area or increase the acceleration voltage. However, when a large number of electron beams are applied, the temperature of the area hit by the electron beam rises, making it susceptible to thermal damage, and metal foils and films are likely to melt during operation, creating holes or deforming them. On the other hand, if the accelerating voltage is increased, the X-ray generating section 9 will expand. In addition, reflected electrons generated when the electron beam 6 is applied to the metal foil or film 21 hit the objective lens, aperture, structural material, etc., generating X-rays and secondary electrons, which become a background signal and noise factor. .

Furthermore, the X-rays generated when the negative electrons pass through the aperture installed near the objective lens pass through the X-ray generation metal foil or film 2I, mix with the X-rays generated here, and are projected. Since another projection image is formed in the center of the image, an unusable portion is created in the projection image.

Furthermore, in the conventional method, Xi7 can only be taken out in the direction in which the electron beam 6 travels.

In other words, conventionally, micro X-ray sources use a single pure metal as metal foil or vapor-deposited thin film, so they have excellent heat resistance, high brightness, and small size, which are desired as micro It has good separation of characteristic X-rays, continuous X-rays, background, and noise, can be extracted in multiple directions, can select energy (wavelength), and can vary the size, brightness, and position of the source. , good reproducibility, and other requirements at the same time, and no one has been established as a good micro X-ray source. Therefore, a projection type X-ray microscope as shown in FIG. 2 has not been manufactured to be of practical use.

Therefore, an object of the present invention is to solve the problems of the conventional miniature X-ray sources described above and to provide a novel miniature X-ray source that satisfies the requirements for the miniature X-ray sources described above.

[Means to solve the problem]

The micro X-ray source of the present invention includes, from the electron beam incident side, a multilayer consisting of a first electron scattering heat diffusion layer, an X-ray generation layer, and a second electron scattering heat diffusion layer, and a direct current connected to the multilayer. a high-voltage power source, a minute hole is provided that penetrates the first electron scattering heat diffusion layer and reaches the X-ray generation layer, and an electron beam for X-ray excitation is made incident on this hole. It is characterized by the fact that

A dielectric layer is provided on the electron beam incident side surface of the first electron scattering heat diffusion layer, and a characteristic X-ray separation continuous X-ray absorption heat reflection layer is provided on the X-ray extraction side surface of the second electron scattering heat diffusion layer,
It is most desirable that the microholes be provided through the dielectric layer and the first electron scattering heat diffusion layer.

Further, the microhole may be in the shape of a pinhole or a V-shaped groove having different depths.

Furthermore, it is preferable that the DC high voltage power source applies a DC voltage to the multilayer that is comparable to or higher than the accelerating voltage of the electron beam.

The DC voltage ranges from plus several 10 keV to minus 1.0 keV with the critical excitation voltage of the X-ray generating metal as the center voltage.
It is in the range of 0 eV.

Furthermore, it is desirable that the DC voltage is variable.

Further, it is preferable that the atomic numbers of the materials constituting the first electron scattering heat diffusion layer, the X-ray generation layer, and the second electron scattering heat diffusion layer are selected to be equal to or smaller in order from the electron beam incident side.

Further, a second electron scattering heat diffusion layer and a second characteristic X-ray separation continuous X-ray absorption heat reflection layer are provided on the side surface of the multilayer near the microhole, so that two directions parallel and perpendicular to the electron beam are provided. It is desirable to be able to extract X-rays from the center in multiple directions.

The above-mentioned micro X-ray source can be used in a projection type X-ray microscope and a micro X-ray diffraction device.

[Effect]

The electron beam incident on the microhole hits the X-ray generation layer at the bottom, forming an X-ray generation section. In this way, the backscattered electrons are confined and do not go out of the multilayer, so the four X-ray generating parts become spherical, and compared to the conventional one, the part corresponding to the spherical head is redundant. generates X-rays. Therefore, without changing the apparent size of the X-ray generating part,
The brightness of the X-ray generating section can be improved. At this time,
Since a DC voltage is applied to the multilayer, reflected electrons and the like are drawn back into the multilayer and absorbed, and do not have any adverse effects.

〔Example〕

Next, the present invention will be described with reference to the sectional view of an embodiment of the present invention shown in FIG.

This minute X-ray source 2 has a dielectric layer 11 . electron scattering heat diffusion layer 12, X-ray generation layer 13,
It consists of a multilayer consisting of an electron scattering heat diffusion layer 14, a characteristic X-ray separation continuous X-ray absorption heat reflection layer 15, and a DC high voltage power supply 19 connected to this multilayer, and also includes an A characteristic X-ray separating continuous X-ray absorbing heat reflecting layer 15' is provided on the side surface of the multilayer near the electron scattering section 10. A pinhole or V-shaped groove 16 with different depths penetrates the dielectric layer 11 and the electron scattering heat diffusion layer 12 and reaches the X-ray generation layer 13.
is provided, and the objective lens 1 (
The electron beam 6 that has been narrowed down by the lens (FIG. 2) is made incident. The minute X-ray source 2 is used in a state where a DC high voltage of plus several OkeV to minus 100 eV is applied by the DC high voltage power supply 19 with the critical excitation voltage of the X-ray generating metal as the center voltage.

The roles of these components are as follows.

The dielectric layer 11 suppresses the generation of reflected electrons at high acceleration voltage,
The generated reflected electrons and stray electrons are unspecified in the electron scattering diffusion layer 1.
2 and the X-ray generation layer 13, and also absorbs X-rays from the electron beam diaphragm near the objective lens 1 to prevent them from reaching the detector 5. One with a large atomic number is desirable.

The electron scattering heat diffusion layer 12 is a layer in which incident electrons have only energy below the critical excitation voltage and releases most of the energy as heat, and has the same thermal conductivity and electrical conductivity as the metal of the X-ray generation layer 13. A substance with a high melting point is used. It is desirable to use a substance with as low an atomic number as possible and a long characteristic X-ray wavelength, such as copper. As described above, the dielectric layer 11 and the electron scattering heat diffusion layer 12 are characterized by having pinholes or V-shaped grooves 16 of different depths leading to the X-ray generation layer 13 to prevent thermal damage. It also serves as a heat diffusion layer.

The X-ray generator 1113 is required to be a material with a high melting point, high thermal conductivity, high electrical conductivity, and high characteristic X-ray intensity.
Gold or its compounds give good results as an X-ray source. When using these compounds, the electron scattering heat diffusion layer 12 must be made of a conductive material.

The electron scattering heat diffusion layer 14 is a layer made of a single element having an atomic number similar to or smaller than that of the X-ray generating substance. X
A high melting point material with good linear transmittance, thermal conductivity, and electrical conductivity is desirable.

The characteristic X-ray separation continuous X-ray absorption heat reflection layer 15 is made of light metal elements or organic compounds such as amorphous carbon and polymer thin films
It consists of one to several thin film layers. The main purpose of this layer is to act as a filter for continuous X-ray absorption, but it also serves to reflect heat rays from the X-ray generation layer 13 and the electron scattering heat diffusion layers 12 and 14. The wavelength selection characteristics of this layer can be changed by changing its thickness, number, and type depending on the purpose of use.

The DC high voltage power supply 19 suppresses the generation of reflected electrons when the X-ray generation layer 13 is irradiated with the electron beam 6, and makes the X-ray generation region 9 variable by changing the accelerating voltage independently of the amount of irradiation current. In particular, the purpose is to reduce and block X-rays generated when passing through the aperture. X1m outlet 18.18'
It also has the role of pulling back transmitted electrons and secondary electrons from heading toward the detector 5.

Next, to explain the operation of this multilayer for a micro X-ray source, this multilayer for a micro 1 and an X-ray detector 5 to obtain a minute X-ray source 2 that converts the energy of an electron beam 6 into X-rays 7. By placing it there, a projection type X-ray microscope is realized.

Several 10 keV to 100 narrowed down by objective lens 1
eV accelerated electrons are passed through pinholes or V-shaped grooves 1 with different depths.
The X-ray generation layer 13 at the bottom of the cell 6 is irradiated. Then, a spherical X-ray generating section 9 is formed.

In the conventional method, as explained in relation to FIG. 3, the electrons at the top become reflected electrons, resulting in the xm generating section 9 having a spherical shape with its head cut off. When the electron beam 6 is irradiated inside the multilayer by using a multilayer with pinholes or V-grooves 16 of different depths, the reflected electrons are trapped and do not come out, so the X-ray The generating section 9 has a spherical shape and generates more X-rays at the portion 17 in FIG. 1 than the conventional one. therefore,
The apparent size of the X-ray generating section 9 remains unchanged (the size seen from below is the same as the conventional one).

), the brightness of the X-ray generating section 9 can be improved by the portion 17. At this time, a direct current voltage comparable to or higher than the accelerating voltage of the electron beam 6 is applied to the multilayers 12 to 14 with the critical excitation voltage of the X-ray generating metal as the central voltage. By operating in this manner, the X-ray generating section 9.17 generates characteristic X-rays, continuous X-rays, and heat, and the electron scattering section 10 generates continuous X-rays and heat. The continuous X-rays in this are absorbed as much as possible by the electron scattering heat diffusion layer 14 and the characteristic Xm separation continuous X-ray absorption heat reflection layer 15, and the heat rays are reflected by the characteristic X-ray separation continuous X-ray absorption heat reflection layer 15.15'. , as shown in FIG.
Take out. Secondary electrons and the like are generated on the surface of the X-ray extraction port 18, 18', but these are absorbed by the multilayer because a normal high voltage is applied to the multilayer by the DC high voltage power supply 19. Since it works as described above, the projection type XWAu
@X-rays generated from a minute point are supplied to the mirror.

According to the experimental results, the electron scattering heat diffusion layer 12, xl
It is desirable that the atomic numbers of the substances constituting the s-generating layer 13 and the electron scattering heat diffusion layer 14 are selected so that they decrease in order from top to bottom.

In addition, there are many combinations of multilayer materials depending on the single metal or compound used for the X-ray generation layer 13 and the type of characteristic X-rays used. There are four possible cases: a case where there are few reflected electrons due to a heavy element, a case where there are many reflected electrons due to a heavy element, a case where the device is used in the atmosphere, and a case where the device is used in a vacuum. however,
In any of these cases, the configuration shown in Figure 1 can be maintained without changing by adjusting the material and thickness of each layer, selecting the depth of pinholes and V-grooves, and adjusting the voltage of the DC high-voltage power supply. It is possible.

By the way, it should be added that the dielectric layer 11 and the characteristic X-ray separation continuous X-ray absorption heat reflection 1115 do not necessarily need to be provided integrally on the surface of the multilayer consisting of the layers 12 to 14 due to their roles.

Note that the minute X-ray source of the present invention can also be used for a minute X-ray diffraction device.

〔Effect of the invention〕

In the micro X-ray source of the present invention, pinholes or V-shaped grooves 16 with different depths are provided in the multilayer, so when the electron beam 6 is irradiated in the multilayer through the pinhole, the reflected electrons are emitted from the multilayer. Since it is trapped inside and does not escape, the X-ray generating section 9 has a spherical shape, and the newly added section 17 can convert the energy that was lost as reflected electron energy in the conventional one into X-ray energy, making it possible to generate heavy When the element is used as the material of the X-ray generation layer 13, the generation xi intensity is 20 to 40.
% could be improved.

In addition, since a DC high-voltage electric current [19] was attached and a positive voltage was applied to the multilayer, reflected electrons could be absorbed by the multilayer.
Secondary electrons generated near the X-ray extraction ports 18 and 18' were also absorbed. In addition, the voltage mentioned above makes it possible to adjust the accelerating voltage of the incident electron beam 6 independently of the current amount at a point other than the voltage applied between the filament of the electron gun and the anode.
The size, brightness, and position of the line generation area 9 can now be controlled.

Furthermore, since the dielectric layer 11 is provided on the surface of the multilayer, it is possible to minimize the amount of disturbance factors such as reflected electrons and X-rays from the aperture and its surroundings that reach the detector 5.

Further, since the electron scattering heat diffusion layers 12 and 14 were provided, the micro X-ray source of the present invention has improved heat resistance and increased durability.

In addition, since the characteristic X-ray separation continuous X-ray absorption heat reflection layer 15.15' is provided on the X-ray extraction port side, the amount of continuous X-rays reaching the detector is reduced, and characteristic X-rays with a good P/B ratio are is obtained,
The contrado of the projected image has improved and thermal noise has disappeared.

Furthermore, it has become possible to extract X-rays from the X-ray extraction ports 18, 18' in multiple directions, centering on two directions parallel and perpendicular to the electron beam 6.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a micro X-ray source according to an embodiment of the present invention, FIG. 2 is a schematic overall configuration diagram of a projection type XWA microscope, and FIG. 3 is an enlarged sectional view of a conventional micro X-ray source. . 1: Objective lens, 2: Micro X-ray source, 3: Measurement sample, 4:
sample support mesh or support membrane, 5: detector, 6: electron beam, 7 generated X-rays, 8; camera section, 9 X-ray generation section, 10:
Electron scattering section, 11: dielectric layer, 12: electron scattering heat diffusion layer, 13: X-ray generation layer, 14: electron scattering heat diffusion layer, 15.
15': Characteristic X-ray separation continuous X-ray absorption heat reflection layer, 16:
Pinhole or 7-shaped groove with different depths, 172 parts that generate extra X-rays, 18.18': X-ray extraction port, 19: DC high voltage power supply, 21: Metal foil Applicant: JEOL Ltd. company

Claims (10)

[Claims] (1) From the electron beam incident side, a first electron scattering heat diffusion layer;
Consisting of a multilayer consisting of an X-ray generation layer and a second electron scattering heat diffusion layer, and a DC high voltage power supply connected to this multilayer,
A fine hole is provided that penetrates the first electron scattering heat diffusion layer and reaches the X-ray generation layer, and an electron beam for X-ray excitation is made to enter the hole. A small X-ray source. (2) A dielectric layer is provided on the electron beam incident side surface of the first electron scattering heat diffusion layer, and a characteristic X-ray separation continuous X-ray absorption heat reflection layer is provided on the X-ray extraction side surface of the second electron scattering heat diffusion layer. 2. The micro X-ray source according to claim 1, wherein the micro hole is provided to penetrate the dielectric layer and the first electron scattering heat diffusion layer. (3) The micro X-ray source according to claim 1 or 2, wherein the micro hole is in the shape of a pinhole or a V-shaped groove with different depths. (4) The micro X-ray according to any one of claims 1 to 3, wherein the DC high voltage power supply applies a DC voltage to the multilayer that is comparable to or higher than the accelerating voltage of the electron beam. source. (5) The DC voltage ranges from plus several 10 keV to minus 100 e with the critical excitation voltage of the X-ray generating metal as the center voltage.
The minute X according to claim 4, characterized in that it is in the range of V.
source. (6) The minute X-ray source according to claim 4 or 5, wherein the DC voltage is variable. (7) The atomic numbers of the substances constituting the first electron scattering heat diffusion layer, the X-ray generation layer, and the second electron scattering heat diffusion layer are selected to be equal to or smaller in order from the electron beam incident side. The minute X-ray source according to any one of claims 1 to 6. (8) A second electron scattering heat diffusion layer and a second characteristic X-ray separation continuous X-ray absorption heat reflection layer are provided on the side surface of the multilayer near the microhole, and two directions, parallel and perpendicular to the electron beam, are provided. 8. The micro X-ray source according to claim 1, wherein X-rays can be extracted in multiple directions around the center. (9) A projection X-ray microscope using the minute X-ray source according to any one of claims 1 to 8. (10) A micro X-ray diffraction apparatus using the micro X-ray source according to any one of claims 1 to 8.