X-ray or gamma ray systems or devices – Specific application – Diffraction – reflection – or scattering analysis
Reexamination Certificate
2000-09-27
2003-03-04
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Diffraction, reflection, or scattering analysis
C378S043000, C378S119000
Reexamination Certificate
active
06529578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an X-ray condenser for condensing X-ray diverging from an X-ray source to a small point, which is suitable for use in an X-ray diffraction apparatus such as an X-ray micro-diffraction apparatus or an X-ray microscope for measuring X-ray diffraction by irradiating a very small region of a sample or a very small sample with X-ray. Further, the present invention relates to an X-ray apparatus constructed with the same X-ray condenser.
2. Description of the Related Art
In an X-ray micro-diffraction apparatus, a micro-area of a sample, etc., is irradiated with an X-ray beam having very small cross sectional diameter and an X-ray information such as diffracted X-ray information, from the sample existing in a field of the irradiation is measured by an X-ray detector. On the other hand, in an X-ray microscope, values of X-ray absorption at discrete positions of a sample under measurement is measured by scanning the sample with an X-ray beam having small cross sectional diameter and detecting intensities of the X-ray transmitted at the respective positions of the sample by an X-ray detector.
In the X-ray apparatus such as the X-ray micro-diffraction apparatus or the X-ray microscope, mentioned above, it is necessary to irradiate a micro-area of a sample with an X-ray, which diverges from an X-ray source and is, preferably, converged on said micro-area. An X-ray condenser is used to converge, namely condense, the diverging X-ray. An example of the X-ray condenser is disclosed in Japanese Patent Application Laid-open No. H8-128970. The disclosed X-ray condenser utilizes an inner surface of a cylinder as an X-ray reflecting mirror and X-ray is condensed to a micro-area by making the inner surface of the cylinder curved.
The disclosed X-ray condenser has a very simple construction and can condense relatively intense X-ray to a micro-area. However, there is a limit in reducing the cross sectional diameter of condensed X-ray. For example, it is very difficult for the disclosed X-ray condenser to reduce the diameter of irradiation area to a value smaller than 10 &mgr;m.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an X-ray condenser capable of condensing X-ray to a very small spot.
Another object of the present invention is to provide an X-ray apparatus capable of performing an X-ray measurement with very high spatial resolution.
According to the present invention, in order to achieve the above mentioned objects, an X-ray condenser for condensing X-ray radiated from an X-ray source to a micro spot is featured by comprising parallel beam forming means for collimating a diverging X-ray from the X-ray source to a parallel X-ray beam and a zone plate disposed in a downstream side of the parallel beam forming means in a propagating direction of the X-ray and constructed by alternately arranging X-ray transmitting bands and X-ray shielding bands.
The zone plate is an X-ray optical component for condensing parallel X-ray beam to a point remote from it by a specific focal distance. Therefore, when a parallel X-ray beam is formed by the parallel beam forming means and the parallel X ray beam is incident on the zone plate, it is possible to condense the X-ray to a micro spot having diameter smaller than 10 &mgr;, which was impossible by the conventional X-ray condenser.
For example, as shown in FIGS.
4
(
a
) and
4
(
b
), the zone plate
11
may be formed by alternately arranging X-ray transmitting bands
12
, which allow X-ray to pass through, and X-ray shielding bands
13
, which do not allow X-ray to pass through. In the structure of the zone plate shown in FIGS.
4
(
a
) and
4
(
b
), the X-ray transmitting bands
12
and the X-ray shielding bands
13
are circular. The zone plate
11
can be manufactured by forming the X-ray shielding bands
13
, which is patterned in a predetermined manner, on an X-ray transparent substrate
14
by a suitable patterning method such as photolithography. In such case, the X-ray transmitting bands
12
are formed by portions of the X-ray transparent substrate
14
, which exist between adjacent X-ray shielding bands.
The X-ray transparent substrate
14
may be formed of, for example, silicon nitride (Si
3
N
4
) or boron nitride (BN). The X-ray shielding bands
13
may be formed of, for example, gold (Au), tantalum (Ta) or nickel (Ni). The number of zones each including a pair of the X-ray transmitting band and the X-ray shielding band is set to, for example, in the order of 300 to 400.
Since the index of refraction of electromagnetic wave in X-ray region is close to “1”, X-ray cannot be focused by using an optical lens for a visible light. The zone plate is used in X-ray region as a substitution for the optical lens. The zone plate takes in the form of, for example, a circular diffraction lattice with which X-ray can be focused. The zone plate having 100 or more zones can be treated in substantially the same manner as a lens used in a usual refractive optics.
In FIG.
4
(
b
), X-ray R
0
radiated from an X-ray source F passes through the X-ray transmitting bands
12
to a condensing spot P. Widths of the X-ray transmitting bands and the X-ray shielding bands are set such that an optical path length of X-ray passing the (m)th X-ray transmitting band is shifted from that passing through the (m+1)th X-ray transmitting band by a wavelength of the X-ray so that all X-ray beams reaching the condensing spot are intensified each other. Thus, the condensing spot P becomes equivalent to a focusing point of an optical lens.
Incidentally, in the present invention, the zone plate may be the so-called phase zone plate. That is, the usual zone plate utilizes the phenomenon that X-ray beams passed through the X-ray transmitting bands are intensified each other by interference so that the X-ray beams are focused. On the other hand, when the thickness of the X-ray shielding bands is reduced such that X-ray can pass therethrough with phase thereof being shifted by a half wavelength, X-ray passed the X-ray shielding bands and X-ray passed through the X-ray transmitting bands are intensified each other by interference to thereby increase the intensity of output X-ray. The zone plate having the latter property is called “phase zone plate”.
In the X-ray condenser according to the present invention, it is preferable to provide spectrometry means capable of picking up X-ray component having a specific wavelength from X-ray containing a plurality of different wavelength components between the parallel beam forming means and the zone plate.
In general, there is the problem of chromatic aberration in the zone plate. That is, when parallel X-ray incident on the zone plate contains X-ray components having different wavelengths, the condensing spot of the X-ray is blurred correspondingly to the wavelength difference, so that it becomes difficult to form micro-X-ray beam having finely defined cross section. However, by monochromatisation of the X-ray incident on the zone plate by means of the spectrometry means, it is possible to reduce the chromatic aberration to thereby prevent the X-ray condensing spot from being blurred.
The spectrometry means is not limited to a spectroscope having a specific structure or to a substance having a specific structure. For example, the spectrometry means may be constructed with using analyzing crystal.
In the X-ray condenser according to the present invention, the parallel beam forming means may be parabolic parallel beam forming means in which diverging beams are made parallel either in horizontal or vertical direction, by utilizing a parabolic surface. By utilizing such parabolic surface, it is possible to form exactly parallel X-ray beams with a simple construction.
In the X-ray condenser according to the present invention, the parallel beam forming means may be parabolic parallel beam forming means in which diverging beams are made parallel both in horizontal and vertical directions, by utilizing a parabolic surface. By forming parallel X-r
Ogiso Katsuhiko
Taguchi Takeyoshi
Bruce David V.
Burns Doane , Swecker, Mathis LLP
Hobden Pamela R.
Rigaku Corporation
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