JP3049790B2 - Imaging soft X-ray microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-resolution imaging soft X-ray microscope mainly for observing a living body.

[0002]

2. Description of the Related Art A conventionally proposed X-ray microscope is:
It is roughly divided into the following four types. First, assuming that there is no optical system, the test object is arranged near the point X-ray source in the divergent light flux of the X-ray generated from the X-ray source, and an X-ray film or two-dimensional An enlarged projection type with an X-ray detector.

[0003] Similarly, assuming that there is no optical system, X
A contact type in which a test object and a resist are disposed in close contact with each other by using a source that supplies a substantially parallel X-ray beam as a radiation source. As an X-ray source in this case, synchrotron radiation (hereinafter, referred to as “X-ray source”)
Simply called SR. ), A plasma X-ray source or an electron beam-excited X-ray source is used. A scanning type in which an X-ray beam is narrowed down to a minute spot by an optical system, and the beam and the object to be scanned are relatively scanned. In this case, an SR is used as an X-ray source, and a Fresnel zone plate (hereinafter simply referred to as FZP) is used as an optical element for narrowing the X-ray beam to a minute spot.

[0004] X-rays are focused on an object to be measured using an SR, an X-ray source composed of a plasma X-ray source or an electron beam-excited X-ray source, and an optical element such as FZP. An imaging type in which an image of an object is formed on a film, a fluorescent screen, or a two-dimensional X-ray detector.

[0005]

SUMMARY OF THE INVENTION As described above, the conventional X
As described below, the X-ray microscope is insufficiently optimized and has a large X-ray irradiation amount, so that it is difficult to observe a living body at a high resolution. That is, in the projection enlargement type, where a high-brightness point X-ray source is required, the intensity is generally insufficient, so that a long-time exposure is required, which makes dynamic observation difficult. Further, in order to avoid a decrease in resolution due to the influence of Fresnel diffraction, it is necessary to slice the object to be inspected, and it is difficult to observe the object alive.

In the contact type, since there is no high-resolution detector other than the resist, development processing of the resist is required, and real-time observation is difficult. In addition, since the magnification is 1, it is necessary to separately perform enlarged observation with an electron microscope or the like. Further, in this case as well, in order to avoid a decrease in resolution due to the influence of Fresnel diffraction, destructive observation such as slicing of the test object is required as in the case of the projection enlargement type.

In the scanning type, an X-ray source having good directivity is required. For this purpose, a large-scale X-ray source such as SR must be used, and there is a disadvantage that the apparatus becomes extremely large. Moreover, the scanning time for obtaining a desired image, that is, the exposure time becomes long, so that dynamic observation is difficult. In the imaging type, when FZP is used, a large-scale X-ray source such as SR is required as a high-intensity X-ray source because the efficiency is low. Further, the imaging type using a mirror has a drawback that it is difficult to improve the resolution and the size of the optical system is large, and the optimization is still insufficient.

In order to solve the above-mentioned problems, the applicant of the present application has previously described an imaging soft X-ray microscope in which X-rays from an X-ray source are covered by a single concave aspheric multilayer mirror condenser. Japanese Patent Application No. 1-206 discloses a configuration in which light is condensed on an inspection object and an image of the inspection object is enlarged and formed on a two-dimensional X-ray image sensor using a phase zone plate PZP as an imaging optical system.
No. 563. He stated that it is effective to use a pulsed laser-excited plasma X-ray source that generates X-rays by focusing a pulsed laser on a target as an X-ray source, and proposed a combination with an optical microscope in the visible region. .

However, depending on the simple combination with the optical microscope in the visible region, it is difficult to easily confirm a narrow visual field with an X-ray microscope, and it is also difficult to perform optical adjustment when combining both microscope optical systems. There was a problem. An object of the present invention is to provide a small-sized imaging X-ray microscope apparatus which can easily confirm a narrow field of view with an X-ray microscope and can easily perform optical adjustment of the X-ray microscope. is there.

[0010]

An X-ray microscope apparatus according to the present invention is based on an image forming type X-ray microscope as disclosed in the above-mentioned Japanese Patent Application No. Hei 1-206563, and the observation field of view of the X-ray microscope. Both the illumination optical system and the objective optical system of the optical microscope for confirming the above are coaxial. That is, a concave aspherical mirror for X-rays is provided on the optical microscope by providing a reflection area for reflecting the illumination light of the optical microscope around the concave aspherical multilayer film mirror condenser as a condensing means of the X-ray illumination system. An imaging optical path formed by a zone plate as an X-ray objective is formed in a through-opening on the optical axis of an objective lens of an optical microscope, while also serving as a condenser condenser.

[0011]

According to the configuration of the present invention as described above, X-rays are reflected and collected at the central portion of the concave aspherical reflecting mirror in the illumination system,
Since the illumination light of the optical microscope can be reflected at the central part and the peripheral part, the concave aspherical reflecting mirror can be used for both the illumination system of the X-ray microscope and the illumination system of the optical microscope. It is possible to efficiently supply illumination light for an optical microscope that requires a larger numerical aperture than an illumination numerical aperture (NA). Therefore, the configuration is simple, and the optical axis of the X-ray microscope can be easily and accurately adjusted by the optical microscope.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated embodiments. FIG. 1 is a diagram showing a schematic configuration of an imaging soft X-ray microscope apparatus according to the present invention. The laser by the pulse laser 1 is condensed by the condenser lens 3 onto the disk or tape-shaped thin film target 5 through the vacuum holding window 4,
Generate X-rays of the required intensity and wavelength. The emission of the pulse laser 1 is controlled by the pulse controller 2 at a desired pulse interval (0.01 to several Hz). X-rays from the X-ray thin film target 5 are condensed on a test object 13 in a test object container 12 by a spheroid multilayer film reflecting mirror 9. Then, using a zone plate (ZP) 14 as an imaging optical system, an object image to be inspected is enlarged and formed on a two-dimensional X-ray imaging device 15. As the two-dimensional X-ray imaging device 15, for example,
A solid-state imaging device such as a back-illuminated FT-CCD is effective.

In such a configuration, as shown in the figure, the X-ray thin film target 5 by the pulse laser is arranged at the first focal point of the spheroid multilayer film reflecting mirror 9, and the test object 13 is arranged at the second focal point. You. Then, X-rays are monochromaticized by the multilayer film reflecting mirror, irradiated with one pulse of X-rays excited and emitted by the pulse laser, and the two-dimensional X-ray imaging device 15 performs photon counting imaging.

Here, in order to observe the test object 13 while keeping it horizontal, the irradiation and observation X-rays are arranged in a vertical direction.
The laser for line excitation was arranged horizontally. Specifically, the angle between the target 5 and the laser beam for excitation is set to about 35 °, and the incident angle of X-rays to the spheroid multilayer film reflecting mirror 9 is set to 65 °.
°. The X-ray thin film target 5 is exchanged, and the scattered matter and other waste removing means 6 and the aperture 7 are configured to irradiate X-rays in a predetermined direction. On the back surface of the spheroid multilayer film reflecting mirror 9 as a condenser, X
A water-cooled cooling device 10 is provided for preventing a temperature rise and deterioration due to absorption of the wire.

Immediately before the object container 12, the field stop 1
1 is provided, and the opening diameter is changed to an appropriate size according to the observation magnification. However, even with the same magnification, an opening having an appropriate diameter is used to prevent flare and improve contrast. . Image information output from the two-dimensional X-ray imaging device 15 is processed by an image processing unit 16 and output to an image output unit 17 such as a display or a printer.

Each of the above components is housed in a vacuum vessel 18 in order to maintain a vacuum from the spheroidal multilayer concave reflector 9 as a condenser to the light receiving surface of the two-dimensional X-ray imaging device 15. Have been. The pressure in the vacuum vessel 18 is maintained at about 10 ^-2 Pa, where the absorption of X-rays can be ignored. Further, since the scattered matter and the like are generated around the X-ray thin film target 5, the removing means 6 and the like are required, so that it is necessary to isolate the X-ray source part by another vacuum vessel 19. I have.

The visible light from the illumination light source 22 for the optical microscope is condensed on the X-ray target 5 via the condenser lens 21 and the dichroic mirror 20 as a light splitter. The focal point is set to coincide with the focal point of the laser beam from the pulse laser 1. The reflected light from the target 5
Is focused on the test object 13 by the spheroidal multilayer film concave reflecting mirror 9 in the same manner as the X-rays from. As shown in the cross-sectional view of FIG. 2 and the plan view of FIG. 3, the spheroid multilayer film concave reflecting mirror 9 has a reflective region 9a dedicated to visible light and a central multilayer reflective region 9b for X-ray reflection at its periphery. Are formed. The visible light reflecting region 9a may be formed by aluminum evaporation. Also,
Since the X-ray reflection multilayer film can considerably reflect visible light, the entire surface of the reflecting mirror 9 is used as an X-ray multilayer mirror, the central part of which is used as an X-ray reflection area, and the entire surface is reflected by visible light. It can also be an area. As described above, by adopting a configuration in which X-rays are reflected at the central portion of the concave reflecting mirror 9 and visible light is reflected at the central portion and the peripheral portion,
For illumination with a relatively small NA (numerical aperture) of the zone plate 14 as an X-ray objective, illumination with a large NA required for the objective lens 23 can be sufficiently ensured while maintaining the coaxial state.

The zone plate 14 as an X-ray objective and the objective lens 23 of the optical microscope are formed coaxially, and the optical path of the X-ray microscope by the zone plate 14 is in a through opening along the optical axis of the objective lens 23 of the optical microscope. Is formed. The details of the configuration of the zone plate 14 and the optical microscope objective lens 23 are shown in FIGS. The lens barrel of the objective lens 23 for the optical microscope has a protruding portion 104 on the object side, and the zone plate 14 is supported therein by a cross-shaped support member 107 as shown in the plan view of FIG. ing. As shown in FIG.
X by the zone plate 14 in the through opening along the optical axis of
A line imaging optical path is formed. Here, as shown in FIG.
Although the optical path of the optical microscope is slightly blocked by the support member 107, a sufficient observation light can be obtained by the opening 108. Further, the image of the object to be inspected is
Strictly, the light beam 102 from the zone plate 14 needs to be a very small but convergent light beam in order to form an enlarged image on the two-dimensional X-ray image sensor 15. The position is slightly closer to the emission light side than the optical focal position of the objective lens 23. For this reason,
As shown in FIG. 4, the light beam 101 from the objective lens 23 is substantially a parallel light beam. Thus, zone plate 1
Since the zone plate 14 and the objective lens 23 are integrally formed so that the object point for the image by the object 4 and the object point for the image by the objective lens 23 coincide with each other, the object to be inspected is moved by the axial movement of the objective lens 23. If the focusing is performed, the focusing of the X-ray microscope by the zone plate 14 is automatically completed. Generally, zone plate 14
Is difficult to focus as an X-ray microscope due to the very small numerical aperture of the objective lens 2 of the optical microscope.
The focus adjustment can be easily performed by the integral structure with the lens 3.

As shown in FIG. 1, an optical microscope objective lens 2
The parallel light beam from 3 is reflected by the oblique perforated reflecting mirror 24, guided to the outside of the vacuum container 18 through the window glass 25, and forms an aerial image 28 via the imaging lens 26 and the optical path bending mirror 27. This aerial image 28 is
And can be observed at a predetermined magnification. In the above embodiment, the image formed by the X-rays and the visible light image are separated by the oblique perforated reflecting mirror 24. However, not only the X-rays but also the visible light If a detector having a characteristic with high sensitivity is used, for example, a CCD, it is possible to make the X-ray microscope and the optical microscope completely coaxial in the observation system. Also, in the spheroid multilayer film concave reflecting mirror 9, the center position (the position on the optical axis) is set so that X is not incident on the optical axis of the X-ray zone plate 14 to cause noise in the image sensor 15. ) Is desirably provided with a minute absorber, for example, a minute body of aluminum.

[0020]

According to the present invention as described above, since the illumination optical system and the objective optical system of the X-ray microscope and the optical microscope are coaxial, it is possible to easily confirm a narrow visual field with the X-ray microscope. In addition, even when a pulsed X-ray source is used as the X-ray source, the optical adjustment of the X-ray microscope is easy. If the focal point of the X-ray microscope and the focal point of the optical microscope are to be made coincident with each other, the X-ray microscope is automatically focused by observing the part to be observed with the X-ray microscope with the optical microscope. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment according to the present invention.

FIG. 2 is a sectional view showing a configuration of a concave reflecting mirror according to the present invention.

FIG. 3 is a plan view showing a configuration of a concave reflecting mirror according to the present invention.

FIG. 4 is a sectional view showing a configuration of an objective optical system according to the present invention.

FIG. 5 is a plan view showing a configuration of an objective optical system according to the present invention.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21K 7/00 G02B 21/00

Claims (3)

(57) [Claims] An X-ray source, a multilayer concave reflector for converging X-rays from the X-ray source on a test object, and a X-ray source for condensing the X-rays from the test object. In an X-ray microscope having a zone plate objective for forming an inspection object image and a two-dimensional X-ray imaging device for detecting an image of the inspection object, an X-ray microscope is provided on an optical axis for forming an optical path of the zone plate objective. An optical microscope objective lens having a through opening along the same axis is provided coaxially with the zone plate, and a reflection area for reflecting illumination light for the optical microscope is provided at least at a peripheral portion of the multilayer film concave reflecting mirror,
An imaging soft X-ray microscope apparatus, wherein the concave reflecting mirror is shared by an X-ray microscope and an optical microscope. 2. An imaging soft X-ray microscope apparatus according to claim 1, wherein said zone plate is mounted in a lens barrel of said optical microscope objective lens protruding toward a test object. 3. The X-ray source has a laser light source and a laser irradiation optical system for guiding light from the laser light source to an X-ray target, and illumination light of the optical microscope is transmitted through the laser irradiation optical system. The imaging soft X-ray microscope apparatus according to claim 1, wherein the light is supplied through an arranged light splitter.