JP3049313B2 - X-ray imaging analysis method and apparatus - 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 imaging analysis method and apparatus. More specifically, the invention of this application provides a new X-ray imaging analysis method and apparatus capable of imaging the positional distribution of various elements existing on the surface of a substance, the interface of a thin film, and the like with high accuracy and in a short time. It is about.

[0002]

2. Description of the Related Art Conventionally, as a method of analyzing a material surface using X-rays, for example, a total reflection X-ray fluorescence analysis method is known. In this total reflection X-ray fluorescence analysis, the penetration of X-rays into a substance is extremely suppressed, and X-ray fluorescence from an element present near the surface of the substance is measured by a semiconductor detector to analyze the substance surface. It is a method of performing. Known as a highly sensitive surface analysis method, it is used for evaluation of contamination of semiconductor wafers, and is applied to various objects such as various industrial materials, environment, and biological samples.

However, in such a total reflection X-ray fluorescence analysis, in order to be incident X-rays to material at a shallow angle of 1～10Mrad, irradiation area on the substance, in particular X-ray optical axis, the irradiation area There was a problem that it became wide. That is, for example, the incident X-ray is limited by a 40 μm wide slit immediately before
When incident at rad, it spreads as wide as 20 mm on the material surface. Usually, the size of a sample handled in the total reflection experiment is about 10 to 30 mm, and in this case, at least in the optical axis direction, a large area on the material surface is X.
Since the radiation is applied, the measurement result of the fluorescent X-ray only gives the average information of the material surface. Naturally, since fluorescent X-rays are divergent light emitted in all directions, it is difficult to analyze the positional distribution of elements on the material surface if the irradiation area is large as described above.

Therefore, in order to obtain a positional distribution of elements on the surface of a substance by detecting fluorescent X-rays, it has been considered to irradiate only a limited place on the sample and scan the sample. In the above-described total reflection X-ray fluorescence spectroscopy, such a scanning type imaging cannot be performed because the incident angle is very small, but a similar surface analysis method has been conventionally used.

This surface analysis method is a method of irradiating a minute area at normal incidence and detecting fluorescent X-rays from the material surface in an oblique emission arrangement, focusing on the reversibility of the optical path by the reciprocity theorem. However, in this method, although it is possible to obtain an image of an element by scanning a sample with an X-ray beam, it takes a very long time of half a day to one day for scanning, and for that, There is a problem in that it is not possible to obtain much resolution and the number of pixels, and it is not possible to simultaneously measure another important information such as a mirror reflectance under total reflection conditions.

The invention of this application has been made in view of the above circumstances, and solves the problems of the prior art.
It is an object of the present invention to provide a new X-ray imaging analysis method and apparatus capable of imaging and analyzing the positional distribution of various elements existing on the surface of a substance or a thin film with high accuracy and in a short time.

[0007]

In order to solve the above-mentioned problems, the invention of this application is directed to X-rays that obtain a positional distribution of an element by imaging a fluorescent X-ray emitted from a substance element with a detector. A line imaging analysis method, wherein the angular divergence of fluorescent X-rays is limited using an angle divergence restricting means placed between a substance and a detector, and the detector and the angle divergence restricting means are brought as close as possible to the substance. An X-ray imaging analysis method (Claim 1) characterized in that X-rays are emitted from an element of a substance when the X-ray is incident on the substance surface at a shallow angle near the critical angle of total reflection. Imaging fluorescent X-rays (claim 2), imaging fluorescent X-rays emitted from a substance element when a particle beam is incident on a material surface at a shallow angle (claim 3), and a radioisotope Adsorb or label Capturing the fluorescent X-rays emitted from this the radioisotope when is, to obtain the positional distribution of the radioisotope (claim 4) or, using a fine tube assembly as angular divergence limiting means ( Claim 5), the use of a one-dimensional detector or a two-dimensional detector as a detector (claim 6), and the like are also provided as such aspects.

Further, the invention of this application is an X-ray imaging analyzer for imaging a fluorescent X-ray emitted from an element of a substance by a detector to obtain a positional distribution of the element. X-rays by the angular divergence limiting means provided is restricted angular divergence of the X-ray fluorescence, and detector and angular divergence limiting means is characterized in that it is placed as close as possible to the substance during the An imaging analyzer (claim 7) is also provided to image fluorescent X-rays emitted from a substance when X-rays are incident on the surface of the substance at a shallow angle near the critical angle of total reflection (claim 8). , imaging the fluorescent X-rays emitted from the material when it is incident on the material surface at a shallow angle particle beam (claim 9) and those the radio when the radioisotope is adsorbed or label material surface Fireflies emitted from isotopes Capturing the X-ray, primary to obtain positional distribution of the radioisotope or (Claim 10), the fine tube assembly as angular divergence limiting means are provided and (Claim 11), as a detector In this case, an original detector or a two-dimensional detector is provided (claim 12).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application is as described above,
A fluorescent X-ray emitted from an element of a substance is imaged by a detector to obtain a positional distribution of the element, and the angular divergence of the fluorescent X-ray is limited by an angle divergence between the substance and the detector. Means, and the detector and the angle divergence limiting means are as close as possible to the substance.

The fluorescent X-rays to be imaged are, for example, X-rays.
When a beam is incident on a material surface at a shallow angle, typically near the critical angle for total reflection, or a particle beam such as an electron beam or ion beam is as shallow as the total reflection of X-rays When the light is made incident on the surface of the substance, it is generated from the vicinity of the surface of the substance. Further, even when the radioisotope is adsorbed or intentionally labeled on the surface of the substance, the radioisotope emits a fluorescent X-ray spontaneously.

The fluorescent X-rays are imaged by a detector whose angle divergence is restricted by an angle divergence restricting means and which is as close to the substance as possible, so that the X-ray fluorescence can be obtained in a shorter time and shorter than the above-mentioned conventional technique. The positional distribution of elements can be obtained with high accuracy. Here, the state as close to the substance as possible means that, when irradiating the surface of the substance with X-rays or particle beams , the state is as close as possible within a range that does not hinder the optical paths of the incident beam and the reflected beam , When the radioisotope is adsorbed or labeled, it means that the detector and the angle divergence restricting means are located as close as possible without contacting the substance.

Therefore, in such a state, the effect of the present invention that the positional distribution of elements can be obtained with high accuracy and in a short time can be realized, and the concrete numerical value representing the distance from the substance itself can be realized. Is not limited.
An example of the distance value from the material surface to the detection element inside the detector is, for example, X having a laboratory level output.
About 0.5 to 5.0 in the case of a radiation or particle source
mm. In the examples described later, the material sample, the microtubule aggregate and the C
The case where a CD camera is arranged is illustrated.

By the way, as the angle divergence restricting means disposed at the position between the detector and the substance as close as possible as described above, an aggregate of fine tubes can be used. This fine tube aggregate has, for example, a structure as illustrated in FIG. 5, that is, a structure in which a glass plate is precisely and regularly drilled, or a structure in which fine glass pipes are regularly arranged and integrated. In this case, the angular divergence of the fluorescent X-rays is limited by the ratio between the inner diameter of the hole (or glass pipe) and the thickness of the glass plate. Such a microtubule aggregate is generally called a capillary plate (or a collimator plate).

Further, there is a so-called microchannel plate having an electrode structure, which has a structure similar to that of the capillary plate and can be used as a fine tube assembly. In addition, by coating the inner walls of the capillaries or channels in these plates, or by processing them to form an aspherical shape, those that have been improved, such as focusing or enlarging the image, Needless to say, as long as the effects of the present invention can be obtained, it can be used as a microtubule aggregate. Of course, the shape of the outer hole of the plate itself can be various, such as circular or rectangular.

As described above, as long as it has a function of restricting the angular divergence of fluorescent X-rays, various known means or means newly prepared to have the function can be replaced with the angle diverging means. Can be used as On the other hand, the detector, the one-dimensional detector to provide information in only one direction, such as horizontal position and height, for example a diode array, MOS image sensor, position sensitive gas proportional <br/> counting tube Do etc. can be used. Alternatively, a two-dimensional detector that gives information on a position represented by XY coordinates, for example, a charge-coupled device (= CCD) camera can also be used. It goes without saying that the two-dimensional detector can also be used as a one-dimensional detector by integrating the obtained information. The resolution of the imaging is governed by the angular divergence of the fluorescent X-rays and the distance from the substance to the detection element, together with the resolution of the detector itself.
High resolution is obtained by making the latter two as small as possible.

The X-ray imaging analysis method and apparatus of the present invention are based on the following idea. Since the incident X-rays hardly penetrate into the substance under the condition of total reflection, the emitted fluorescent X-rays are limited to those from the elements near the surface, and are therefore stronger than the fluorescent X-ray intensity in ordinary solid analysis. No attempt was made as in the invention of this application under total internal reflection conditions, since it is not considered to be of high intensity, and further attenuation is considered to be more remarkable through the angle divergence control means.

However, the geometric factors are very important, for example the distance between the substance, the angular divergence limiting means and the detector (eg its Be window and its internal elements in the case of a CCD camera) are possible. By shortening as much as possible, it is possible to suppress the angular divergence of fluorescent X-rays diverging in all directions from any position on the substance, and a 1: 1 correspondence between the sample position and the detector position can be obtained. High strength can be ensured, so that the positional distribution of elements on the material surface can be obtained.

Further, under the condition of total reflection, attention is paid to the special feature that the optical path of the X-ray is almost parallel to the surface of the substance, and such a close contact arrangement can be realized by utilizing the spatial space facing the substance. Therefore, the present invention has been made. According to the present invention based on such an idea, an image of one million pixels can be obtained with a resolution of, for example, several tens of microns in about several minutes. If used, element identification can be easily performed by an operation such as changing the energy of incident X-rays before and after the absorption edge of the element.

That is, as compared with the conventional vertical incidence and oblique emission scanning type surface analysis method as described above, the resolution, the number of pixels and the measurement time, or the convenience of simultaneous measurement with the specular reflectance etc. It is excellent and can analyze the positional distribution of elements existing near the material surface with extremely high accuracy and in a short time. Of course, not only in the case of X-ray fluorescence, but also in X-ray fluorescence
The above-described principle can be used for imaging of fluorescent X-rays spontaneously emitted by a line or a radioisotope.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0021]

(Embodiment 1) FIG. 1 is a schematic view showing an embodiment of an X-ray imaging analyzer according to the present invention. For example, X shown in FIG.
In the line imaging analyzer, the angle divergence control means has a diameter of 6 mm.
A collimator plate (1), which is a collection of microtubes having a diameter of about 10 mm and formed into a disc with a small diameter of about 10 mm in total by assembling glass tubes having a thickness of about 1 mm and a thickness of about 1 mm, is placed directly above the sample (3) at a distance of about 5 mm. together are installed in the back of the collimator plates (1), as close as possible with the collimator plates (1), one pixel about 12 [mu m square, 1,000,000 pixels CCD type device (CCD) camera (2 ) Is installed.

As the sample (3) in this embodiment, an aqueous solution of copper ions and zinc ions (concentration 1000 ppm, about 5 μl) was dropped and dried on a silicon wafer as illustrated in FIG. ing. In the rectangular frame (white line) in the figure, a copper ion aqueous solution is present on the left and a zinc ion aqueous solution is on the right. A synchrotron radiation light source is provided as the X-ray source (4), and monochromatic radiation X-rays are used.

After the X-ray monochromatic radiation from the synchrotron radiation source passes through the slit (5) and the two-crystal monochromator (6), the optical path width in the horizontal direction is restricted by the slit (7) having a width of 100 μm. The sample (3) passes through the incident intensity detector (8) and passes through a small angle smaller than the critical angle.
And is totally reflected on the surface of the sample (3), and the fluorescent X-rays generated from the vicinity of the surface of the sample (3) are collimated by the collimator plate (1) disposed close to the sample (3). The angular divergence is limited (that is, parallelized) by the camera, and an image is taken by the CCD camera (2).

At this time, as described above, since the collimator plate (1) is formed by assembling glass tubes having a diameter of 6 μm and a thickness of 1 mm, the angle divergence of fluorescent X-rays is limited to 6/1000. Will be. With such an X-ray imaging analyzer, fluorescent X-rays from the sample (3) were imaged in each case using 9.8 keV monochromatic X-rays and 9.0 keV monochromatic X-rays. The imaging time is 5 minutes.

FIGS. 3 and 4 are photographs instead of drawings illustrating the results of X-ray fluorescence imaging in the case of 9.8 keV and 9.0 keV monochromatic X-rays, respectively. 9.8keV single color X
The line produces both copper and zinc fluorescent X-rays,
In the case of 9.0 keV monochromatic X-rays, only fluorescent X-rays of copper are generated. Therefore, by comparing FIGS. 3 and 4, images of copper and zinc can be obtained. In both figures, it can be seen that the left side of the two strong spots is a copper droplet trace and the right side is a zinc droplet trace. That is, a result that corresponds well to the image in FIG. 2 can be obtained.

From the size of the droplet, it can be determined that the spatial resolution here is about 30 microns. Further, even when a smaller amount of a copper ion aqueous solution was dropped on a silicon wafer and dried, a fluorescent X-ray of copper could be similarly imaged with high accuracy. As described above, imaging was performed by distinguishing different kinds of metals near the surface of the sample (3).

Embodiment 2 In Embodiment 1 described above, a synchrotron radiation light source is used as the X-ray source (4), and radiation X-rays are incident.
In the second embodiment, X-ray fluorescence imaging is performed using an ordinary laboratory X-ray source. X-ray source in the illustrated X-ray IMAGING analyzer in Figure 1 as (4), a copper rotating anode X-ray source (40 kV-80 mA, 6-degree directional focus size = 30.mu.
m × 3 mm), a copper cut α-ray from a copper rotating anti-cathode X-ray source is taken out by a channel cut monochromator, and a horizontal optical path width is restricted by a slit (7) having a width of 40 μm. As in 1, the light is incident on the sample (3) at a small angle smaller than the critical angle.

At this time, C is passed through the collimator plate (1).
The X-ray image picked up by the CD camera (2) has an absorption edge of copper K
It is limited to those of fluorescent X-rays from elements lower than the energy of α1 ray. When there are not many types of elements and the distribution image is of interest, sufficiently simple imaging can be obtained by simple imaging alone. Further, it is also possible to perform element identification determination by placing a filter such as a metal foil having a thickness of several μm or the like immediately before the collimator plate (1) and taking an image, and examining an image change due to the presence or absence of the filter. .

The above embodiment relates to imaging of fluorescent X-rays emitted from the sample (3) when X-rays are incident at a shallow angle near the critical angle of total reflection on the surface of the sample (3). However, in the same manner, when the particle beam is incident at an angle as shallow as the total reflection of the X-ray, the fluorescent X-ray and the spontaneous fluorescent X-ray from the radioisotope adsorbed or labeled on the material surface are similarly observed. It is needless to say that imaging can be performed with high accuracy and in a short time, and the positional distribution of elements and the radioisotope existing on the surface of a substance or an interface of a thin film can be easily analyzed with excellent accuracy.

Of course, the present invention is not limited to the above examples, and various embodiments are possible in detail.

[0031]

As described in detail above, according to the present invention, it is possible to image and analyze the positional distribution of various elements present on the surface of a substance or the surface or interface of a thin film with high accuracy and in a short time. A new X-ray imaging analysis method and apparatus is provided, which enables a significant advancement of analysis technology, thereby promoting the improvement of the manufacturing process and in various industries. It is possible to realize the production of high-quality industrial products.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram illustrating an X-ray imaging analyzer according to an embodiment of the present invention;

FIG. 2 is a photograph replacing a drawing illustrating a sample.

FIG. 3 is a photograph instead of a drawing illustrating an X-ray image obtained by 9.8 keV monochromatic X-rays.

FIG. 4 is a photograph replacing a drawing illustrating an X-ray image obtained by 9.0 keV monochromatic X-rays.

FIG. 5 is a perspective view showing an example of a capillary plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Collimator board 2 CCD camera 3 Sample 4 X-ray source 5 Slit 6 2 Crystal monochromator 7 Slit 8 Incident intensity detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-282243 (JP, A) JP-A-1-282452 (JP, A) JP-A-7-49316 (JP, A) JP-A 8-282 285798 (JP, A) JP-A-6-27056 (JP, A) JP-A-7-280753 (JP, A) JP-A-3-76200 (JP, U) JP-A-6-65809 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 23/00-23/227 G01T 7/00

Claims (12)

(57) [Claims] 1. An X-ray image analysis method for imaging a fluorescent X-ray emitted from an element of a substance by a detector to obtain a positional distribution of the element, wherein the angular divergence of the fluorescent X-ray is determined by the substance. An X-ray imaging analysis method characterized in that the angle divergence limiting means placed between the detector and the detector is limited, and the detector and the angle divergence limiting means are brought as close as possible to the substance. 2. The X-ray imaging analysis method according to claim 1, wherein when X-rays are incident on the surface of the substance at a shallow angle near the critical angle of total reflection, fluorescent X-rays emitted from the element of the substance are imaged. 3. The X-ray imaging analysis method according to claim 1, wherein when the particle beam is incident on the surface of the substance at a shallow angle, the fluorescent X-ray emitted from the element of the substance is imaged. 4. capturing the fluorescent X-rays emitted from this the radioisotope when adsorbed or label radioisotope material surface, X-rays imaging analysis according to claim 1 for obtaining the positional distribution of radioisotope Method. 5. The X-ray imaging analysis method according to claim 1, wherein a microtubule aggregate is used as the angle divergence limiting means. 6. The X-ray imaging analysis method according to claim 1 , wherein a one-dimensional detector or a two-dimensional detector is used as the detector. 7. A fluorescent X-rays emitted from the elements of material captured by the detector, an X-ray imaging spectrometer to obtain a positional distribution of elements, the angle between the detector and the material An X-ray imaging analyzer characterized in that the divergence limiting means is provided to limit the angular divergence of fluorescent X-rays, and the detector and the angle divergence limiting means are arranged as close as possible to the substance. . 8. The X-ray imaging analyzer according to claim 7, wherein when the X-rays are incident on the surface of the material at a shallow angle near the critical angle of total reflection, the fluorescent X-rays emitted from the material are imaged. 9. The X-ray imaging analyzer according to claim 7, wherein when the particle beam is incident on the material surface at a shallow angle, the fluorescent X-ray emitted from the material is imaged. 10. radioisotope imaging the fluorescent X-rays emitted from this the radioisotope when adsorbed or label material surface, X-rays imaging analysis according to claim 7 to obtain the positional distribution of radioisotope apparatus. 11. The X-ray imaging analyzer according to claim 7, wherein a microtubule aggregate is provided as angle divergence limiting means. 12. The X-ray imaging analyzer according to claim 7, wherein a one-dimensional detector or a two-dimensional detector is provided as the detector.