JP3028675B2 - X-ray scanning device - 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 scanning device for scanning an X-ray micro beam.

[0002]

2. Description of the Related Art Conventionally, when scanning a micro beam on a sample, the beam itself is moved by vibrating a reflecting mirror or a voltage applied to a deflection plate, or a sample stage supporting the sample is moved. The method is taken. For example, in a laser irradiation apparatus that scans a laser in the visible region, the irradiation position is set by vibrating a reflecting mirror and shaking a laser beam incident on one point on the reflecting mirror. In a scanning electron microscope, a scanning image is obtained by fixing an electromagnetic lens and a sample and oscillating an electron beam with a deflection plate. In a scanning X-ray microscope, a scanning image is obtained by moving a sample while fixing an optical system.

[0003] In the case of an X-ray micro beam, a method of oscillating a reflecting mirror using a light source having a small spread angle of the X-ray is considered. However, the reflectivity of the X-ray reflector is
Since it largely depends on the incident angle of the X-ray, the reflectance changes greatly when the X-ray incident angle changes due to the vibration of the reflecting mirror. Therefore, when the vibrating mirror is vibrated during scanning, the intensity of X-rays reflected by the vibrating mirror changes,
There arises a problem that the intensity of the micro beam irradiated on the sample surface cannot be made constant. In addition, since X-rays have no charge, a deflecting plate cannot be used. Therefore, conventionally, X
When scanning a line microbeam, a method has been adopted in which the sample stage is moved in a plane orthogonal to the beam while the irradiation position of the microbeam is fixed.

[0004]

However, in the use of an X-ray microbeam, it is sometimes undesirable or impossible to move a sample. For example, in an experiment in which X-ray microbeam irradiation is performed together with an electrophysiological technique, a sample is pierced with several glass microcapillary electrodes, which are fixed to a micromanipulator. Therefore, when the sample is moved, the sample is damaged by the electrode, and the electrode is bent to change the resistance value, which affects the measurement.

When irradiating a sample floating in water with an X-ray microbeam, the sample does not move together with the sample tank due to inertial force even when the sample tank is moved, and it is difficult to obtain a clear scanning image. Also, it was difficult to set the irradiation position of the X-ray microbeam. The present invention has been made in view of such a problem, and has a fixed strength X-ray on a sample surface with the sample fixed.
It is an object of the present invention to provide an X-ray scanning device capable of scanning with a line microbeam.

[0006]

In order to achieve the above object, an X-ray scanning apparatus according to the present invention comprises: an X-ray source; a reflecting means capable of reflecting and oscillating X-rays emitted from the X-ray source; An X-ray optical element for converting the X-ray reflected by the means into a microbeam, wherein the reflecting means is disposed at a position which substantially divides a distance between the X-ray source and a principal point of the X-ray optical element by approximately two. An X-ray scanning device, comprising:

In addition, the X-ray source may not be a radiation source itself that emits X-rays, but may be an aperture that is focused on X-rays emitted from another X-ray source and arranged at a conjugate point with respect to the X-ray source. .

[0008]

According to the present invention, the angle of incidence of X-rays that are reflected by a reflecting mirror into microbeams is always constant even when the reflecting mirror vibrates. Therefore, the reflectivity of the X-rays at the reflecting mirror is also constant, and the intensity of the micro beam irradiated on the sample surface is always equal.

The principle of the present invention will be described below with reference to FIG. Here, the description will be made using the oblique incident angle instead of the incident angle, but this does not change in principle. X-rays emitted from the X-ray source A are reflected by the vibrating mirror 2 and then condensed by the X-ray optical element 3 to form a micro beam on the sample surface. The position of the X-ray source is A, the center of the vibrating mirror is O, and the principal point of the X-ray optical element is P. One end of the vibrating mirror 2 when the X-ray reflected at the center O of the vibrating mirror is directed to the principal point P of the X-ray optical element 3 is M ₁ , the oblique incidence angle of the X-ray at that time is θ ₁ , and the position of the microbeam is B ₁ , a virtual image of A by the vibrating mirror 2 is defined as A ₁ (this state is referred to as a first state). When the vibrating mirror 2 is slightly tilted from the first state, one end of the vibrating mirror 2 is M ₂ , the oblique incidence angle of X-ray is θ ₂ , the position of the micro beam is B ₂ ,
A virtual image of A and A ₂ by (this state is referred to as a second state).

In the second state, the X-rays reflected by the vibrating mirror 2 toward the principal point P of the X-ray optical element 3 are reflected at points N (A ₂ P and M ₂ O) different from the center O of the vibrating mirror. X-rays reflected at (intersection point of). That the straight lines M ₁ O and M ₂ O are the perpendicular bisectors of the straight lines AA ₁ and AA ₂ respectively
it is obvious. Also, since the distance between AO and OP is set equal, the lengths of OP, OA ₁ and OA ₂ are equal. That is, the triangle OA ₂ P is an isosceles triangle. Since ∠A ₁ OA ₂ is one outer angle of the triangle OA ₂ P, it can be expressed as と A ₁ OA ₂ = ∠OA ₂ N + ∠OPN = 2∠OPN. Therefore, ΔOPN can be expressed by the following equation.

[0011]

(Equation 1)

In the second state, the oblique incidence angle ∠AN of the X-rays toward the principal point P of the X-ray optical element 3 with respect to the vibrating mirror 2
O can be represented by the following formula.

[0013]

(Equation 2)

In other words, the X-rays traveling toward the principal point P of the X-ray optical element 3 are always incident on the vibrating mirror 2 at the same oblique incident angle, even if the vibrating mirror 2 vibrates. You are doing. On the other hand, when AO and OP are different, the above equations do not hold, and the oblique incidence angle changes due to the vibration of the reflecting mirror.

[0015]

Embodiment 1 FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. The X-ray micro-beam scanning device of the present embodiment
An X-ray source 1, a vibrating mirror 2 configured to reflect and oscillate X-rays emitted from the X-ray source 1 and an X-ray collector for condensing X-rays and forming a microbeam on a sample surface 4 And an optical element 3. In the drawings, a vacuum container incorporating the above components and an exhaust device for evacuating the inside of the container to a vacuum are omitted.

The X-ray source 1 is composed of a target 1a and an electron beam optical system 1b. By irradiating the target 1a with an electron beam excited by the electron beam optical system 1b, a characteristic X-ray corresponding to the target 1a is obtained. Generate. In this embodiment, a carbon thin film is used as a target, and a wavelength of 4.5 is used.
X-rays of nm are generated. The vibrating mirror 2 was formed by coating a glass substrate with platinum as a reflection surface. Further, another substance such as silicon carbide may be used. The X-ray optical element 3 for collecting X-rays is configured by providing a zone plate formed of gold on a silicon nitride film. Since X-rays pass through the silicon nitride film but do not transmit gold, X-rays can be focused on the sample 4 by diffraction of the zone plate by appropriately setting the dimensions of the zone plate. As the X-ray optical element 3, a spherical or aspherical reflecting mirror may be used instead of the zone plate.

In such a configuration, X-rays emitted from the X-ray source 1 enter the vibrating mirror 2. X for vibrating mirror 2
The X-rays are reflected on the entire reflecting surface on which the rays are incident, but only the X-ray flux incident on the zone plate of the X-ray optical element 3 out of the reflected X-rays is condensed and functions as a micro beam. At this time, only the X-ray near the specific incident angle is always taken out by the X-ray optical element 3 regardless of the inclination of the vibrating mirror 2. The X-rays condensed by the X-ray optical element 3 form an X-ray microbeam and irradiate the sample surface 4. Scanning on the sample surface 4 is performed by vibrating the vibrating mirror 2 in the direction of the arrow by means not shown.

In this embodiment, the distance between the X-ray source 1 and the vibration center of the vibrating mirror 2 and the distance from the vibration center to the zone plate are set to 1 m. The distance from the zone plate to the sample surface 4 was set to 20 cm. At this time, if the size of the X-ray source 1 is 100 μm, a 10 μm microbeam is formed on the sample surface 4. When the oblique incidence angle of the X-rays on the vibration center of the vibrating mirror 2 was set to 3 ± 1 °, the scanning range on the sample surface 4 was approximately ± 3.5 mm. In this case, the length of the vibrating mirror 2 needs to be about 70 cm.

[0019]

Embodiment 2 FIG. 2 is a schematic configuration diagram showing a second embodiment of the present invention. The X-ray microbeam scanning apparatus according to the present embodiment includes an X-ray source 1, a condenser mirror 5 for condensing X-rays emitted from the X-ray source 1, and a conjugate point in the condenser mirror 5 of the X-ray source 1. An opening 6 disposed, a vibrating mirror 2 configured to reflect and vibrate the X-rays passing through the opening 6 and an X-ray condensing element for condensing the X-rays and forming a micro beam on the sample surface 4 3 is provided. In the drawings, a vacuum container incorporating the above components and an exhaust device for evacuating the inside of the container to a vacuum are omitted.

The X-ray source 1 includes a target 1a and a laser source 1
c and the laser light emitted from the laser source 1c
This is a plasma X-ray source composed of a lens 1d for focusing light on a. In the present embodiment, carbon was used for the target 1a, and a YAG laser was used for the laser source 1c. The target 1a was irradiated with a YAG laser through the lens 1d to generate plasma, and X-rays having a wavelength of 3.4 nm were generated from the plasma. The condenser mirror 5 is composed of a multilayer film of a combination of Ni—Cr (alloy) and V ₂ O ₅ , and collects X-rays emitted from the X-ray source 1. Vibrating mirror 2 and X-ray optical element (zone plate) 3
Are the same as in the first embodiment.

In this embodiment, since the opening 6 can be regarded as an X-ray source, the distance between the opening 6 and the center of vibration of the vibrating mirror 2 is substantially equal to the distance from the center of vibration to the zone plate. Just set it. Therefore, the degree of freedom in arranging the optical system can be increased. In addition,
In the present embodiment, the X-ray source 1 is a laser plasma X-ray source.
May be incident.

In the present invention, it is possible to use a multilayer film as the movable mirror. In this case, the components may be arranged similarly to the first or second embodiment, and the vibrating mirror 2 may be a multilayer mirror. The multilayer film that reflects X-rays is formed by alternately stacking a plurality of substances with high accuracy. Assuming that the period of the multilayer film is d, the wavelength of the X-rays is λ, and the oblique incidence angle of the X-rays is θ, the incident X-ray wavelength λ and the oblique incidence angle θ are Brad's condition 2d sin θ = mλ (m is a natural number) When the above condition is satisfied, a high reflectivity is exhibited for this X-ray (actually, incident light having a certain wavelength width Δλ with respect to the wavelength λ and a certain angle width Δθ with respect to the angle θ is also reflected). For example, if λ and d are equal,
Even under conditions where θ deviates greatly from oblique incidence of 30 °, X
Lines can be reflected.

The distance between the components is set to the same value as in the first embodiment, and the vibrating mirror 2 used in the first and second embodiments is made of Ni—Cr (alloy) having a period d of 3.4 nm and V ₂ O _5. , The length of the vibrating mirror 2 is 7cm
Was enough. As a result, the moving mirror can be made smaller than in the case where a total reflection mirror is used, and the device can be made smaller. Since the cycle of the multilayer film can be artificially changed, when used for a vibrating mirror, the incident angle of X-rays to the vibrating mirror can be arbitrarily set.

The wavelength of the X-ray used in the present invention is not limited to 4.5 nm or 3.4 nm shown in the embodiment. For example, a vibrating mirror composed of a multilayer film of a combination of tungsten and carbon can be used for characteristic X-rays of copper having a wavelength of 0.154 nm. For light having a wavelength in the soft X-ray region of 13 nm, a normal reflecting mirror or a multilayer film of a combination of molybdenum and silicon can be used as a vibrating mirror.

In this embodiment, the center position of the vibrating mirror is set to be a position that bisects the X-ray source (or an opening provided at a conjugate point thereof) and the principal point of the X-ray optical element. ,
It is not necessary to be exactly at this position. For example, if a vibrating mirror composed of a multilayer film is used, the multilayer film also reflects X-rays incident with a certain angle width Δθ with respect to the oblique incidence angle θ of the principal ray. For example, if the principal ray can tolerate ± θ up to ± 0.2 °, the oblique incidence angle of the principal ray to the center of the vibrating mirror is 30
When set to {± 1}, the ratio of the distance between the aperture of the X-ray source or its conjugate point and the distance from the principal point of the X-ray optical element to the vibrating mirror is within the range of 4: 6 to 6: 4. I just need. Therefore,
Actually, even if the optical system is set to fall within this range,
Similar effects can be obtained.

[0026]

According to the present invention, a fixed sample can be scanned with an X-ray microbeam at a constant intensity. Further, when a reflecting mirror made of a multilayer film is used as a vibrating mirror, the vibrating mirror can be downsized. Furthermore, since the angle of incidence of X-rays on this vibrating mirror can be selected in a wide range,
There is also an advantage that the degree of freedom of arrangement of the scanning optical system is increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment.

FIG. 2 is a schematic configuration diagram of a second embodiment.

FIG. 3 is an explanatory diagram showing the principle of the present invention.

[Explanation of Signs of Main Parts]

 DESCRIPTION OF SYMBOLS 1 X-ray source 1a Target 1b Electron beam system 1c Laser source 1d Lens 2 Vibrating mirror (reflection means) 3 X-ray optical element 4 Sample surface 5 Condensing mirror 6 Opening

Claims (3)

(57) [Claims] 1. An X-ray source, a reflecting means capable of reflecting and oscillating an X-ray emitted from the X-ray source, and an X-ray optical element for making the X-ray reflected by the reflecting means a micro beam. ,
An X-ray scanning apparatus according to claim 1, wherein said reflecting means is arranged at a position which substantially divides a distance between said X-ray source and a principal point of said X-ray optical element by two. 2. An X-ray scanning apparatus according to claim 1, wherein said X-ray source comprises an opening arranged at a position where X-rays emitted from another X-ray source are collected. 3. An X-ray scanning apparatus according to claim 1, wherein said reflection means comprises a multilayer film.