JPH08334565A - X-ray detection apparatus - Google Patents

Abstract

PURPOSE: To obtain an X-ray detection apparatus by which X-rays at a high energy can be measured and by which the two-dimensional spatial distribution of the X-rays can be observed by moving a hole which is made in the front of a light receiving face on an X-ray detection element and through which the X-rays can be passed only in a fine region on the light receiving face. CONSTITUTION: Thin-film electrodes 2 are installed on both faces of a high-resistance single-crystal Si plate 1, and a photodiode 3 is constituted. The light receiving time of the photodiode 3 is set, only one X-ray photon is made incident on the Si plate 1, and a signal obtained by guiding a generated electric charge to the electrodes 2 is amplified 4. The value of a generated electric-charge amount which is found on the basis of the intensity of the signal is converted into energy which the photon has, and the value is stored in a corresponding channel inside a multichannel analyzer 5. At this time, a lead thin plate 8 for X-ray shielding, which is insatlled in the front of a light receiving part is moved by a device 9, a hole 7 having a diameter of about 10μm, which is made in the thin plate 8 is moved to the in-plane direction, and X-rays are measured in each set position of the hole 7. Then, spectrum data which has been stored 5 is transmitted to a large-capacity storage device 10, and an energy spectrum is displayed 6 by a two-dimensional lattice corresponding to the set position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an X-ray detector suitable for evaluating the material state of an object by detecting the X-ray emitted from an object to be inspected by X-ray irradiation and calculating the energy thereof. Regarding

[0002]

2. Description of the Related Art For measuring X-ray energy, a semiconductor X-ray detector (S.S.S.) which is composed of a scintillation counter or a substrate of Si (silicon) or Ge (germanium) is used.
Day, Solid State Detector SSD S
The solid state detector is mainly used, and the latter is widely used because of its high energy resolution. In recent years, X as well as these detectors
The energy of the ray can be measured, and the X-ray measurement can be performed in two dimensions (that is, the spatial intensity distribution of the X-ray can be observed). CCD (charge coupled device), CCD (Charge) Coupled De
The research and development of an X-ray detector composed of a Vice) is being conducted. Both the SSD and CCD described above measure X-ray energy by utilizing the fact that the number of charges generated in the substrate when an X-ray photon is incident on the semiconductor substrate of the light receiving portion is proportional to the energy of the incident photon. To do. The electric charge generated in the substrate is guided to an electrode provided on the surface of the substrate and detected as an electric signal.

[0003]

The CCD has the advantage that the spatial distribution of X-rays can be observed and the energy of X-rays at each position in this space can be measured. It is expected as a detector of an analyzer for analyzing the structure of the object to be inspected by evaluating the energy distribution of the X-rays in. However, it has a drawback that the detection sensitivity to X-rays having an energy of about 10 keV or more is extremely low as compared with SSD. This is because when a high-energy X-ray photon is incident, the X-ray photon easily penetrates deep into the semiconductor substrate, and charges generated in the deep portion of the substrate by the X-ray photon reach an electrode provided on the substrate surface. This is because the probability of recombination and disappearance is high.
In order to accurately measure the energy of incident photons up to high energies, it is necessary to prevent the reduction of the charge generated by this recombination as much as possible. In order to prevent this, it is necessary to increase the resistance of the semiconductor substrate of the detection unit to about 10 kΩ or higher. However, if the resistance is increased, the charges generated inside the substrate diffuse in the in-plane direction of the substrate before reaching the electrode on the surface and ooze out to the adjacent pixel region of the CCD, which deteriorates the spatial detection resolution and the energy resolution. Also,
Since a high-resistance Si substrate is not used for a general optical CCD, it is difficult to obtain it.

The problem to be solved by the present invention is to provide an X-ray detector capable of measuring even high-energy X-rays and observing the two-dimensional spatial distribution of the X-rays. .

[0005]

In order to solve the above problems, the present invention uses a single photodiode type X-ray detecting element having an area, such as SSD, and a fine photo diode is provided on the front surface of the light receiving portion of the detector. A shield plate (opening member) having a hole (opening) through which only X-rays can pass is provided, and X-ray detection is performed so as to move the hole (opening) in the in-plane direction (desirably two-dimensional direction) on the light receiving surface. Make up the department. Furthermore, a storage device that stores (or holds) the energy spectrum (measurement data) of the X-ray measured at each set position on the light-receiving surface of the X-ray detection element of the opening of the X-ray detection unit, and a storage device that stores it. An X-ray detection device in which the above-mentioned X-ray detection unit is combined with a display device that rearranges (preferably two-dimensionally) displays the measured data (or information based on it) corresponding to the measurement position. Configure the system.

In the X-ray detector of the present invention, the position of the above-mentioned opening member with respect to the light receiving surface may be fixed depending on the application (in this case, the X-ray detector is movable in the X-ray incident direction). Further, it is desirable that the light receiving surface is always covered with the opening member when viewed from the X-ray incident direction. When scanning the position of the opening member with respect to the light receiving surface to move the opening in the in-plane direction on the light receiving surface, the scanning is performed. Therefore, it is important to increase the area of the opening member so that the light receiving surface is not exposed to the X-ray incident direction side. The above-mentioned X-ray detection element is not limited to SSD as long as it has a function of analyzing the energy of each X-ray photon incident on the light-receiving surface (that is, energy dispersive type). For example, X-ray detection made of a superconductor. You may use what has a part. It is desirable that the opening member be electrically conductive, and the influence of charging of the member by X-rays (so-called non-measurement target) that is irradiated onto the surface of the member that cannot pass through the opening provided in the opening member is removed. it can.

The means for scanning the position of the aperture member with respect to the light receiving surface inputs the scanning control signal to the storage device or the display device described above, and cooperates with the spatial distribution measurement of the X-ray intensity and the storage or display of the measurement data. I would like you to do it. Further, the above-described storage device may be configured to temporarily store the measurement data, delete the data after transmitting the data to the display device.

[0008]

According to the above X-ray detecting apparatus, the position of the opening member is scanned with respect to the light receiving surface of the X-ray detecting element,
An X-ray aerial image (image of the sample to be observed) can be observed, and the X-ray energy at each position can be measured. In the two-dimensional rearrangement of the spectrum data obtained at each position by the hole movement, when the energy of a certain range is simultaneously displayed in the spectrum data at each position, it corresponds to a color image in a general optical imager. You can get a statue. Also, if only X-rays having a desired specific energy are extracted and rearranged, a monochromatic X-ray two-dimensional image can be obtained. This corresponds to a monochrome image in general optical imaging. In particular, the latter is effective for X-ray diffraction measurement.

[0009]

【Example】

 (Embodiment 1) An embodiment of the present invention will be described with reference to FIG.

100 kΩ having an area of 300 mm ^2.
A high-resistance single crystal Si plate 1 having a size of cm was prepared, and thin film electrodes 2 capable of transmitting X-rays were provided on both surfaces of the plate to form a photodiode 3 having an X-ray receiving area of 250 mm ² . When the photodiode is ready to receive light, only one X-ray photon S
The light receiving time was set so that the light was incident on the i-plate, the charges generated in the Si plate by the photon incidence were guided to the electrodes provided on the plate surface, and the signal obtained at this time was amplified by the amplifier 4.
The generated charge amount is calculated from this signal intensity, and this value is converted into the energy possessed by the photon, and the signal 1 indicating that one photon is incident on the corresponding energy channel in the multi-channel analyzer 5 is stored. . After repeating this light reception and storage, the data stored in the previous channel is read out and the energy spectrum is displayed on the display device 6.
It can be displayed on.

An X-ray shielding Pb (lead) thin plate 8 having a thickness of 100 μm having a hole 7 having a diameter of 10 μm is provided in the front portion of the light receiving portion of the X-ray energy detector having the above structure. A device 9 for moving the thin plate is provided so that the hole in the thin plate can be moved in the in-plane direction at the front part of the light receiving surface. The X-ray was measured at each set position of this hole, and the spectrum data once stored in the multi-channel analyzer was transferred to the mass storage device 10. Next, the two-dimensional grating 11 shown in FIG. 2 was provided on the display device in correspondence with the set position. Each of the cells 12 of this grid has substantially the same size as the hole provided in the Pb plate, and corresponds to the set position in the front portion of the light receiving surface. This unit mass corresponds to one pixel in the CCD. All the spectral data obtained at each position of the hole are displayed in the mass portion corresponding to the set value of the hole. The multi-channel analyzer used in this example has 4096 channels, and the 4096th channel corresponds to X-ray energy of 40.96 keV. Therefore, the minimum step of the spectrum data is 10 eV of X-ray energy corresponding to one channel.
In the above display, a display color was assigned for every 10 eV of energy. Then, an X-ray detection device 13 including these constituent elements was produced.

Next, the X-ray analysis apparatus 14 shown in FIG. 3 was produced using this X-ray detection apparatus. A fine white X-ray beam 15 having a diameter of 0.8 μm is applied to an LSI (LSI, so-called highly integrated circuit) 16 which is an object to be inspected. The spatial distribution image was observed with the above detection device. When the two-dimensional lattice image obtained at this time was displayed, a color image similar to that of a normal CCD image pickup camera was obtained. In the observed image, although the display colors were different, there were a plurality of spots or high-luminance regions distributed in a ring shape. One spot part is selected from these areas, and the X-ray energy spectrum in that part is shown in FIG.
It was shown to. The main component of this spectrum was X-rays 17 diffracted by a minute portion of the LSI, and other than that, it was composed of fluorescent X-rays 18 and scattered X-rays 19 showing the constituent elements of the inspection object. Further, the energies of the diffracted X-rays in the spectra of the respective spots are different, which corresponds to the different display colors of the respective spots and rings in the two-dimensional image. In the region other than the spot or the ring-shaped portion, the above spectrum showed a spectrum in which the diffracted X-ray component was removed. Therefore, it can be seen that the two-dimensional image in which the high-luminance portion is extracted is the back reflection Laue image of X-ray diffraction. Crystal analysis of the LSI wiring and the Si substrate in the X-ray irradiation part was performed from this Laue image. In addition, by extracting only a specific fluorescent X-ray component over the entire area of the two-dimensional image and using the sum thereof, it is possible to analyze the trace elements in the minute portion. As described above, by using the X-ray detection apparatus of the present invention, it becomes possible to simultaneously perform the crystal structure analysis and the elemental analysis in the minute portion of the inspection object having a complicated structure such as LSI.

By crossing two slits and passing X-rays through the holes formed at the intersections, the same function as that of the X-ray shield plate having the fine holes can be provided. Needless to say. Further, when only one slit is used instead of the above shielding plate, it moves in only one direction within the light receiving surface, so that a one-dimensional distribution image is obtained on the display device.

(Embodiment 2) An embodiment of the present invention will be described with reference to FIG.

The X-ray detection device 13 has the same function as that of the first embodiment, but as shown in FIG. 5, the light-receiving surface of the detection device can be rotated around the X-ray irradiated portion 21 of the inspection object 16. It is possible to move back and forth toward this center and also to move in the in-plane direction of the light receiving part. Further, a two-dimensional image is obtained at the set position of the light receiving element 3 by the same method as in the first embodiment, the light receiving element is moved in the in-plane direction, a two-dimensional image is obtained at each light receiving element set position, and each two-dimensional image is obtained. The light receiving elements are arranged corresponding to the set positions so that a large area X-ray space two-dimensional distribution image can be displayed. As a result,
In the first embodiment, the region in which the spatial distribution of X-rays can be observed was limited to only one light receiving surface, whereas in the present embodiment, the second
The three-dimensional observation region can be arbitrarily expanded to the range where the light receiving element can be moved, and a wider range X-ray spatial distribution image can be observed. In FIG. 5, this X-ray detection device is arranged behind the object to be inspected,
By observing the two-dimensional space image at this time, the transmission Laue X-ray diffraction measurement method can be applied.

(Embodiment 3) This embodiment will be described with reference to FIG.

The structure of the analyzer 14 is the same as that of the first and second embodiments, but in addition to the X-ray detector 13 according to the present invention, in order to measure the brightness of X-rays transmitted through the object to be inspected, A scintillation counter 22 is arranged on the opposite side of the primary irradiation X-ray beam 15 with the object 16 sandwiched therebetween. This counter is provided to confirm the X-ray irradiation position.
The primary X-ray beam and the scintillation counter are fixed, the inspection object between them is moved in the direction perpendicular to the optical axis of the beam, and the total number of photons detected at each moving position can be held in the storage device 10. I did it. This operation is performed over the entire area of the object to be inspected so that the respective brightness data thus obtained can be rearranged on the display device 6 in correspondence with the set position of the object to be inspected. The brightness of this transmitted beam is the primary X
It depends on the X-ray transmissivity in the beam irradiation part, that is, it changes depending on the material and structure in the irradiation part of the inspection object. Therefore, a two-dimensional transmission image similar to an ordinary projection type X-ray microscope image was obtained on the display device. In the method of the present embodiment, the finer the irradiation X-ray beam is and the shorter the moving distance of one step of the inspection object is, the more the resolution and magnification of the obtained two-dimensional image are improved.

Next, based on this image, the object to be inspected is moved to a position corresponding to a position on the image, whereby the X-ray beam can be irradiated to a desired local position, and the X-ray at that position can be irradiated. Analysis such as line diffraction measurement has become possible. In this example, the scintillation counter was used to obtain the transmission image, but the irradiation position of the X-ray beam can be determined by the same method using the X-ray detection device of the present invention. In this case, the X installed on the front surface of the light receiving surface which is the main part of the present invention.
The line shielding plate was removed. The scintillation counter could not identify transmitted X-rays having various energies, but in this case, a transmission image in which the X-ray energy was identified could be obtained. By using this function, it was found that there is an advantage that structural analysis in the depth direction of the inspection object can be performed. First, a two-dimensional transmission image similar to the case of using a scintillation counter by irradiating a primary beam of white X-rays was displayed on a display device. next,
The high-energy components in the image were sequentially removed by computer processing. Along with this, the two-dimensional image that was visible before removal (FIG. 7a) gradually changed, and other patterns 23 and 24 emerged from places other than the contrast pattern 22 that was initially visible (FIG. 7A). 7
b, c). This indicates that there is a region having high absorption efficiency for low energy X-rays even in a region where high energy X-rays are hardly absorbed and transmitted. The energy dependence of this pattern indicates that the materials constituting each pattern or their structures such as the layer thickness are different.

FIG. 7 is an observation of an LSI pattern formed on a Si substrate. After obtaining this transmission image, each pattern position is irradiated with a fine X-ray beam and irradiated with the X-ray detector of the present invention. Radiation X-rays from the same surface as the X-ray irradiation surface were detected by rotating around the position. From the energy spectrum analysis of the fluorescent X-rays obtained at this time, the pattern 22 is
b, Zn (zinc), Ti (titanium) layer, pattern 23 is Pt (platinum), and pattern 24 is Cu
It was found to be composed of (copper). Next, X-ray diffraction measurement was performed in the same manner as in Example 1, and crystal analysis was performed. As a result, the pattern 22 was a compound of the above elements, and the other patterns were electrode layers composed of each element, and each layer By evaluating the dependence of the diffracted X-rays on the X-ray irradiation angle, the stress in each pattern layer and its surroundings could be evaluated.

When the scintillation counter is used, it is difficult to identify the transmitted X-ray energy in the pattern portion, and thus it is difficult to recognize the positions of the patterns 23 and 24.

[0021]

The CCD can measure the spatial distribution and energy of X-rays, but it is a special CCD because it requires a high-resistance Si substrate, which is difficult to manufacture, difficult to obtain, and expensive. There is. In the present invention, since the single photodiode is used for the light receiving portion and the structure is simple, it is easy to manufacture, easy to obtain, and inexpensive. And CC
Similar to D, the spatial distribution image of the X-rays emitted from the irradiated portion and the energy spectrum at each spatial position can be obtained at the same time. Furthermore, since X-ray measurement can be performed in a space as wide as that of the conventional photographic film method, and individual X-ray photons, which are difficult with the photographic method, can be detected, extremely weak X-rays can be detected.
Line measurement is possible. These effects enable high-sensitivity detection required when performing analysis using a fine X-ray beam, so that X-ray diffraction for performing crystal or stress analysis of a minute portion and elemental analysis can be performed. Fluorescent X-ray analysis can be performed.

[0022]

[Brief description of drawings]

FIG. 1 is a diagram illustrating a basic structure of the present invention and an explanatory diagram of a first embodiment.

FIG. 2 is a diagram showing a two-dimensional display grid for displaying a detected X-ray distribution image according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram of an X-ray analysis apparatus using the detection apparatus of the present invention.

FIG. 4 is a diagram showing an X-ray energy spectrum obtained by measurement of a minute portion of an LSI in Example 1.

FIG. 5 is an explanatory diagram of a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of Embodiment 3 of the present invention.

FIG. 7 is a diagram showing an X-ray transmission image of the inspection object obtained in Example 3;

[Explanation of symbols]

1 ... High resistance single crystal Si substrate, 2 ... Thin film electrode, 3 ...
Photodiode, 4 ... Amplifier, 5 ... Multi-channel analyzer, 6 ... Display device, 7 ... X-ray transmission hole, 8 ... X-ray shielding Pb thin plate, 9 ... Shielding plate moving device, 10 ... Mass storage device, 11 ... Display two-dimensional grid, 12 ... Display unit mass in two-dimensional display grid, 1
3 ... X-ray detector, 14 ... X-ray analyzer, 15 ...
White X-ray beam, 16 ... Inspected object, 17 ... Diffraction X
X-ray, 18 ... Fluorescent X-ray, 19 ... Scattered X-ray, 20 ... X-ray irradiation position on inspected object, 21 ... Scintillation counter, 22, 23, 24 ... X-ray transmission image, 25 ...
X-ray generator, 26 ... Fine X-ray beam forming mechanism, 27 ...
… X-rays emitted from the inspection object, 28 …… Analysis room, 29
...... Inspection object moving mechanism, 30 …… Display device screen.

Claims (4)

[Claims] 1. An energy-dispersive X-ray detection element having a light-receiving surface for detecting X-rays, and an opening member arranged so as to shield the light-receiving surface and having an opening smaller than the area of the light-receiving portion. An X-ray detection device characterized by the above. 2. The X-ray detection apparatus according to claim 1, wherein the opening member is movable in an in-plane direction of the light receiving surface. 3. An energy dispersive X-ray detection element having a light-receiving surface for detecting X-rays, and an opening member arranged so as to shield the light-receiving surface and having an opening smaller than the area of the light-receiving portion. Moving means for moving the opening in the in-plane direction of the light receiving surface, storage means for storing the energy spectrum of the X-ray measured by the X-ray detecting element for each position of the opening on the light receiving surface, and the opening. An X-ray detection apparatus comprising: a display unit that displays information based on the energy spectrum measured at the position corresponding to the position on the light receiving surface of the. 4. A sample holding means for holding a sample, an X-ray irradiation means for irradiating the sample with X-rays, an X-ray detection means for detecting X-rays from the sample, and an X-ray detection means for the X-ray detection means. The X-ray detecting means comprises a moving means for moving the sample holding means, and the X-ray detecting means has an X-ray detecting element having a light-receiving surface for detecting X-rays, and is arranged so as to shield the light-receiving surface of the light-receiving portion. An opening member having an opening smaller than the area, moving means for moving the opening in the in-plane direction of the light-receiving surface, and data measured by the X-ray detection element for each position of the opening on the light-receiving surface are stored. An X-ray detection apparatus comprising: a storage unit for storing the information and a display unit for displaying information based on the data measured at the position corresponding to the position of the opening on the light receiving surface.