JP2685243B2 - X-ray optical system and its alignment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an X-ray optical system used to obtain X-ray tomographic images of various objects and an alignment method thereof.

(Prior Art) For example, when obtaining an X-ray tomographic image of a circuit pattern formed on a silicon wafer or the like, as shown in FIG. 4, a walter mirror, which is one type of toroidal total reflection type X-ray optical element, is used. Used. In FIG. 4, 101 is a first reflecting surface composed of a rotating hyperboloid, 102 is a second reflecting surface composed of a spheroid, 103 is an object point, and 104 is an image point. The light emitted from the object point 103 is reflected once by each of the first reflecting surface 101 and the second reflecting surface 102 and reaches the image point 104. Such a total reflection type X
The line optical system has a feature that it has no chromatic aberration and can be aligned with visible light, and the alignment has been conventionally performed with visible light.

FIG. 5 is an explanatory view showing the procedure of alignment and image formation by X-ray, in which 201 is a first reflecting surface and 202 is a second reflecting surface.
A reflecting surface, 203 is a visible light source, 204 is a visible shielding plate, 205 is an image plane, 206 is an X-ray source, and 207 is an X-ray shielding plate. Here, it is assumed that the water mirror 200 having the above configuration is aligned with the image plane 205. First, the water mirror 20
In order to adjust the posture of 0 to the image plane 205 perpendicularly,
The mirror 20 is provided with a shield plate 204 that shields only visible light reaching 205.
Fix to 0. This shield plate 204 may be anything as long as it is opaque in the visible light range. By fixing the shield plate 204, the once-reflected light 209 by the second reflection surface 202,
Two types of visible light, which is the twice-reflected light 210 by the second reflecting surface, can pass through. Next, since the two types of visible light form an annulus at the image plane 205, the attitude of the walter mirror 200 is adjusted so that the annuli are concentric with each other. Next, the visible light shielding plate 204 is removed and the X-ray shielding plate 207 is replaced without changing the attitude of the water-type mirror 200. The shield plate 207 is made of a material that is opaque to the soft X-ray region and has a size that allows only the twice-reflective X-rays reflected by the first and second reflecting surfaces to pass through. Mirror in this way
X from the X-ray source 206 when the alignment of 200 is completed
Imaging with lines.

According to such an alignment method, the once-reflected light 209 by the second reflection surface and the twice-reflected light 2 by the first and second reflection surfaces 2
Since the posture of the mirror 200 may be adjusted so that the two kinds of visible light of 10 form a concentric ring on the image plane 205, the visible light source 203
Alignment becomes possible.

(Problems to be Solved by the Invention) However, as can be seen from the above alignment procedure,
When the visible light alignment is complete, the mirror 20
The visible light shielding plate 204 must be removed and the X-ray shielding plate 207 must be attached without changing the posture of 0 at all. This also applies to the configuration in which the alignment is performed by X-rays instead of visible light. For this reason, it becomes very difficult to maintain the attitude of the mirror 200 at the attitude at the end of the alignment, and the accuracy of the X-ray image formed on the image plane 205 decreases due to the change of the attitude at the end of the alignment. There was a problem.

It is an object of the present invention to provide an X-ray optical system and an alignment method therefor capable of maintaining a posture at the end of alignment with high precision and preventing deterioration of precision of an X-ray image.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the invention of claim 1 shares a first reflecting surface made of a rotating hyperboloid and one pole of the rotating hyperboloid. A second reflecting surface composed of a spheroidal surface sharing the optical axis, and by reflecting the X-ray emitted from the object point surface twice on the first reflecting surface and the second reflecting surface, an image plane is formed. An X-ray optical system including a total reflection X-ray optical element for forming an image, the first reflection surface or the second reflection surface of the total reflection X-ray optical element being arranged on the optical axis from the object point surface. The first that shields X-rays that directly reach the image plane without being reflected by the reflecting surface
X-rays which are arranged on the image plane and are emitted from the object plane and are reflected only once by the second reflecting surface of the total reflection type X-ray optical element to reach the image plane. And a second shielding plate for shielding.

The invention according to claim 2 has a first reflecting surface formed of a rotating hyperboloid and a second reflecting surface formed of a spheroid that shares one pole of the rotating hyperboloid and shares an optical axis, An X-ray optical system including a total reflection X-ray optical element for forming an image on an image plane by reflecting X-rays emitted from an object point surface twice on the first reflection surface and the second reflection surface. In the alignment method, at the time of alignment with respect to the image plane of the total reflection type X-ray optical element, an image is obtained from the object point surface without reflection on the first reflection surface or the second reflection surface of the total reflection type X-ray optical element. A first shielding plate that shields visible light and X-rays that reach the surface directly is arranged on the optical axis, and when the image is formed by the X-rays emitted from the object plane, the first shielding plate is In addition, the total reflection type X-ray optical element is emitted from the object point surface, and It reflected and once only by the reflecting surface of the second shielding plate for shielding X-rays reaching the image surface, characterized in that disposed in the image plane.

Further, the invention of claim 3 has a first reflecting surface made of a rotating hyperboloid and a second reflecting surface made of a spheroid that shares one pole of the rotating hyperboloid and shares an optical axis, An X-ray optical system comprising: a total reflection type X-ray optical element for forming an image on an image plane by reflecting X-rays emitted from an object point surface twice on the first reflection surface and the second reflection surface. A visible light that is formed of a material that does not transmit both visible light and X-rays and that directly reaches the image plane without being reflected by the first reflection surface or the second reflection surface of the total reflection type X-ray optical element; A first disk-shaped shield that shields X-rays, and is formed of a material that is arranged concentrically with the first disk-shaped shield and that transmits visible light and does not transmit X-rays. X-rays that are reflected only once by the second reflection surface of the X-ray optical element and reach the image plane A shielding plate having a second circular annular shielding portion for 蔽 characterized by being disposed on the optical axis.

(Operation) When the alignment is performed using the wide visible range, as described above, the light reflected once by the second reflection surface of the total reflection type X-ray optical element and the light reflected twice by the first and second reflection surfaces are generated. Will be needed.
Therefore, first, a first shield plate that shields only the light that passes through these two types of light and directly reaches the image plane is provided, and this first shield plate is inserted into the optical element. This shielding plate uses a material that shields both the visible light region and the soft X-ray region. next,
When the image is formed by x-ray, unnecessary unnecessary reflected light is removed,
A second shielding plate that allows only the twice-reflected light to pass therethrough is inserted, and a material that is impermeable to the soft X-ray region is used for this second shielding plate.

Therefore, even if the alignment is completed, it is not necessary to remove the first shield plate, and only the second shield plate is inserted.
Since the second shield plate only excludes the light reflected once,
The accuracy of the insertion position may be slightly lower.

As for the other configuration of the present invention, the first and second shielding portions having the same function as the first and second shielding plates are provided on the inner peripheral side and the outer peripheral side of one shielding plate. However, it is only necessary to insert the shielding plate once, and the alignment can be performed more efficiently.

(Example) Hereinafter, an example of the present invention is described with reference to drawings.

FIG. 1 shows an embodiment of an X-ray optical system according to the present invention along the alignment procedure. In the figure, 30
0 is the first reflection surface of the total reflection type X-ray optical element 310, and 301 is the second
A reflecting surface, 302 is an image plane, 303 is an object plane, 304 is a first shielding plate that shields only light that directly reaches the image plane 302 without being reflected by the total reflection X-ray optical element 310 once, Reference numeral 306 denotes the light reflected once by the second reflecting surface 301, and 307 denotes the first and second reflecting surfaces 300, 30.
The twice-reflected light by 1 and 308 is a second shielding plate that cuts the once-reflected light 306. In the figure, (a) and (b) represent separately the optical paths of two types of reflected light during alignment with visible light. First, a visible light point light source (see FIG. (Not shown), and the first shield plate 304
Is inserted and fixed, and the total reflection X-ray optical element 310 is aligned. In this case, since the lights (a) and (b) are simultaneously generated, the two types of light 30 are observed when observed from the back side of the image plane 302.
The posture of the optical element 310 is determined so that 6,307 are concentric. Next, as shown in (c) in the figure, a second shielding plate 308 that excludes the reflected light once is inserted in the vicinity of the image plane 302, a sample is placed on the object plane 303, and the object plane 303 is illuminated with X-rays to form an image. An enlarged X-ray image of the sample is obtained on the surface 302. At this time, the once-reflected X-rays are emitted from the second shielding plate 308.
It is excluded by and does not reach the image plane 302.

According to this configuration and the alignment method, even if the positioning of the shield plate 304 for the purpose of excluding the direct light is slightly bad and the direct light leaks, the light is excluded by the second shield plate 308 and reaches the image plane 302. There is no. Regarding the second shielding plate 308 for the purpose of excluding the once-reflected light 306, since the twice-reflected light 307 and the once-reflected light 306 are spatially separated in the vicinity of the image plane 302, The positioning can be easily performed. Furthermore, after the alignment is completed, when the second shield plate 308 is inserted, there is no fear that the alignment state of the optical element 310 will change, so the imaging accuracy of the optical system can be improved.

FIG. 2 is a plan view showing another embodiment of the shield plate used in the X-ray optical system according to the present invention. In the figure, 401 is thickness 5
A disk-shaped optical glass having a size of about mm, 402 is a portion where gold (Au) is deposited on the optical glass 401 in a concentric circular shape by several tens of μm. However, various metals can be used for the vapor deposition portion 402 in consideration of the absorption coefficient and the thickness. Then 403
Is an arm for fixing the shielding plate 400 to the outer frame, and 404 is a frame. The shield plate 400 is fixed to the entrance surface of the X-ray optical element. With this configuration, the width of the entrance pupil of the optical system in the visible light region is 405, and that in the X-ray region is 406.

FIG. 3 is a diagram showing an example of alignment and image formation of the X-ray optical element having this configuration, and shows an enlargement system here. (It is also possible to reduce the size).

FIG. 3 (a) shows the alignment during visible light (b)
In the figure, 501 is a visible light source, 502 is an X-ray source, 503 is a first reflecting surface, and 504 is a second reflecting surface.

In this configuration, when aligning the attitude of the X-ray optical element 310, as described above, the light reflected once by the second reflection surface 504 by the second reflection surface 504 and the first and second reflection surfaces 50 are observed.
In order to control the posture of the optical element 310 so that the double ring formed by the twice-reflected light 408 by 3,504 is concentric, it is necessary that the above two types of light reach the image plane 405. Therefore, the third
As shown in FIG. 5A, the radius of the vapor deposition portion 402 is set to a size that shields only the light that directly reaches the image plane. Accordingly, the portion of the optical glass 401 on the outer side is transparent to the visible light region, and thus does not block the two types of light.

Next, considering image formation by X-ray, the necessary light rays are
Only the X-rays are reflected twice by the first reflecting surface 503 and the second reflecting surface 504 once in total. Therefore, as shown in FIG. 3B, the radius of the disk-shaped optical glass 401 is set to a size such that only the twice-reflected X-rays pass through and all other X-rays are shielded. If the thickness of the optical glass is about 5 mm, it can be considered that the soft X-ray region is almost opaque. Therefore, the size of the shielding plate 400 for X-rays is determined by the optical glass diameter.

Therefore, according to this embodiment, it is possible to save the trouble of newly inserting another shield plate after performing alignment with visible light, and it is possible to perform more accurate alignment. Further, since only one kind of shield plate needs to be prepared, the management thereof becomes easy.

[Effects of the Invention] As described above, according to the present invention, a means for blocking light that directly reaches the image plane without being reflected by the total reflection type optical element once, and once for the second reflecting surface. Since the means for blocking the reflected light is configured as the same shield plate or separate shield plates and is inserted into the total reflection type optical element to perform alignment, the total reflection type optical element is placed in a high posture at the end of the alignment. The X-ray image can be formed while maintaining the accuracy, which can greatly contribute to the improvement of the accuracy of the X-ray image.

[Brief description of the drawings]

1A to 1C are diagrams showing the X-ray optical system according to the present invention in the order of alignment, and FIG. 2 is a plan view showing another embodiment of a shielding plate used in the X-ray optical system of the present invention. FIG. 3 is an explanatory view for explaining the alignment operation and the X-ray image forming operation using the shielding plate of FIG. 2, and FIG. 4 is a general view of an X-ray optical system using a total reflection type optical element. FIG. 5 is a schematic diagram for explaining the alignment and the image forming operation of the X-ray image. 101 ... First reflection surface, 102 ... Second reflection surface, 103 ... Object point, 104 ... Image point, 310 ... Total reflection type X-ray optical element, 201,
300,503 …… first reflecting surface, 202,301,504 …… second reflecting surface,
203,501 …… Visible light source, 204 …… Visible light shielding plate, 205,30
2,405 ... Image plane, 206,502 ... X-ray source, 207 ... X-ray shielding plate, 209,306,407 ... Single reflected light, 210,307 ... Double reflected light, 303 ... Object point, 304 ... First Shielding plate, 308 ... Second shielding plate, 400 ... Shielding plate, 401 ... Optical glass, 402
...... Gold evaporated part, 403 ...... arm, 404 ...... frame.

Claims (3)

(57) [Claims] 1. A first reflecting surface composed of a rotating hyperboloid and a second reflecting surface composed of a spheroidal surface sharing one optical pole of the rotating hyperboloid and sharing an optical axis. An X-ray optical system comprising: a total reflection X-ray optical element that forms an image on an image plane by reflecting emitted X-rays twice on the first reflecting surface and the second reflecting surface, A first shield plate which is arranged above and shields X-rays that directly reach the image plane from the object point surface without being reflected by the first reflection surface or the second reflection surface of the total reflection type X-ray optical element. A second shield that is disposed on the image plane, shields X-rays emitted from the object plane, reflected once only by the second reflecting surface of the total reflection X-ray optical element, and arriving at the image plane. An X-ray optical system, comprising: 2. A first reflecting surface formed of a rotating hyperboloid and a second reflecting surface formed of a spheroid that shares one optical pole of the rotating hyperboloid and shares an optical axis. An alignment method of an X-ray optical system, comprising: a total reflection X-ray optical element that forms an image on an image plane by reflecting emitted X-rays twice on the first reflecting surface and the second reflecting surface, At the time of alignment with respect to the image plane of the total reflection type X-ray optical element, the first total reflection type X-ray optical element is moved from the object point plane.
A first shielding plate that shields visible light and X-rays that directly reach the image surface without being reflected by the reflecting surface or the second reflecting surface is arranged on the optical axis, and X emitted from the object point surface is arranged. At the time of imaging by a line, in addition to the first shield plate, the light is emitted from the object point surface and is reflected once only by the second reflection surface of the total reflection type X-ray optical element to reach the image plane. A second shielding plate that shields the X-rays to be arranged is arranged on the image plane. 3. A first reflecting surface consisting of a rotating hyperboloid and a second reflecting surface consisting of a spheroid that shares one pole of the rotating hyperboloid and shares an optical axis. An X-ray optical system comprising: a total reflection X-ray optical element that forms an image on an image plane by reflecting emitted X-rays twice on the first reflecting surface and the second reflecting surface, Made of a material that does not transmit both X-rays,
A first disc-shaped shield that shields visible light and X-rays that directly reach the image plane without being reflected by the first reflection surface or the second reflection surface of the total reflection type X-ray optical element; It is arranged concentrically with the first disc-shaped shield and is made of a material that transmits visible light and does not transmit X-rays, and is reflected only once by the second reflecting surface of the total reflection X-ray optical element. An X-ray optical system, wherein a shield plate having a second ring-shaped shield portion for shielding X-rays reaching the image plane is arranged on the optical axis.