JP2005062169A - X-ray detection element and x-ray detector using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray detection element that can exclude scattered X rays efficiently with a simple structure, has high sensitivity, and integrates a collimator, and to provide an X-ray detector using the X-ray detection element. <P>SOLUTION: In the X-ray detection element, an X-ray detection semiconductor having a number of X-ray detection elements arranged one-dimensionally, and an X-ray obstruction member are overlapped alternately for lamination. The X-ray detector utilizing the X-ray detection element comprises the X-ray detection element; a bias application section for applying a bias voltage to the X-ray detection element; and a reading section for reading a signal from the X-ray detection element via wiring. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an X-ray detection element that directly converts an X-ray photon into an electric signal and an X-ray detection apparatus using the X-ray photon, and particularly to an X-ray detection element that is provided with a collimator integrally and an X-ray detection apparatus using the X-ray detection element.

  In diagnostic apparatuses using X-rays such as an X-ray CT apparatus and an X-ray fluoroscopic apparatus, a collimator is usually provided in front of the X-ray detector in order to remove X-rays scattered by the subject, Among the radiated X-rays, the one that has passed through the subject can be detected.

  Various proposals have been made as such collimators. For example, in Patent Document 1, in a collimator that passes X-rays that pass through a subject for each section formed by a plurality of collimator plates, the pitch of the arrangement of the collimator plates in the vicinity of the end in the width direction of the collimator is set. A collimator having a sparser pitch than the arrangement pitch near the center of the collimator has been proposed.

  In Patent Document 2, an X-ray conversion layer that has electrodes on the upper and lower surfaces and converts X-rays directly into a charge signal, and a collimator unit composed of a collimator plate for removing scattered radiation are one-dimensional or two-dimensional. In a radiation detector arranged in a shape, a photosensitive glass plate is used as a substrate, the collimator plate is inserted and fixed in a groove formed by etching, and a plurality of sub-substrates provided with an X-ray conversion layer on the back surface are arranged in multiple stages. There has been proposed a radiation detector that is configured so that the wiring on the main substrate is formed so that the electrical wiring of each sub-substrate can be shared, and the X-ray conversion layers are arranged oppositely or in the same direction.

Japanese Patent Laid-Open No. 2003-207575 JP 2002-90463 A

  However, these conventional collimators have the problem that they are complex and large devices. In addition, some metal plates that form a collimator require a reinforcing member such as an intermediate material or a support member, which absorbs transmitted X-rays from the subject, and thus the sensitivity of the X-ray detection apparatus is lowered. .

  In view of such a conventional problem, the present invention can efficiently eliminate scattered X-rays with a simple structure, and has a highly sensitive X-ray detection element integrally provided with a collimator and an X-ray using the same. An object is to provide a detection device.

  The X-ray detection element according to the present invention is formed by alternately stacking X-ray detection semiconductors having a large number of X-ray detection elements arranged one-dimensionally and X-ray blocking members.

  In the above invention, a number of one-dimensionally arranged X-ray detection elements are arranged such that p + regions are arranged in stripes on one surface layer portion of a silicon n-type semiconductor substrate, and n + regions corresponding to the p + regions are arranged on the other surface layer portion. It is preferable that n + regions are arranged in stripes on one surface layer portion of the silicon p-type semiconductor substrate, and p + regions corresponding to the n + regions are disposed on the other surface layer portion. be able to.

  Furthermore, the X-ray sensing element is preferably adapted to receive the emitted X-rays in the longitudinal direction of the striped p + or n + region, and the longitudinal length of the striped p + or n + region is 20 It is preferably ˜50 mm.

  The X-ray blocking member preferably has a protrusion amount of 20 to 40 mm from the X-ray detection element, and preferably has a plate thickness of 40 to 100 μm. Further, the X-ray blocking member is preferably provided with inclined surfaces having an inclination angle of 0.05 to 0.1 ° on both end surfaces of the X-ray blocking member.

  The X-ray detection apparatus using the X-ray detection element includes the X-ray detection element, a bias applying unit that applies a bias voltage to the X-ray detection element, and a signal from the X-ray detection element via wiring. And a reading unit for reading out.

  The X-ray detection element according to the present invention is configured integrally with an X-ray detection semiconductor in which an X-ray blocking member having a collimator function detects X-rays, and efficiently eliminates scattered X-rays with a simple structure. Can do. Further, the X-ray detection semiconductor can be easily manufactured by a widely used method for manufacturing a silicon semiconductor. Furthermore, a high-sensitivity and compact X-ray detection apparatus can be configured using this X-ray detection element.

  An embodiment of the X-ray detection element according to the present invention will be described below with reference to the drawings. A cross section of the present X-ray detection element 100 is shown in FIG. 1, and a plan view is shown in FIG. As shown in FIG. 1, the X-ray detection element 100 is formed by alternately stacking X-ray detection semiconductors 10 and X-ray blocking members 20.

In this example, the X-ray detection semiconductor 10 is composed of a silicon n-type semiconductor substrate, an SiO ₂ layer 14 is formed on the outermost layer of the upper surface layer portion, and a lower portion of the SiO ₂ layer 14 is shown in FIG. Thus, the p + regions 12 are arranged in a striped pattern. On the other hand, a layered n + region 13 corresponding to the p + region 12 is formed in the lower surface layer portion of the X-ray detection semiconductor 10, and a layered Al electrode 15 is formed in the lower portion thereof. A depletion layer 11 is formed between the p + region 12 and the n + region 13.

The present X-ray detection semiconductor 10 can be manufactured by a method similar to a known silicon strip detector (SSD). The total thickness of the X-ray detection semiconductor 10 including the SiO ₂ layer 14 to the Al electrode 15 is 200 to 600 μm, and the thicknesses of the SiO ₂ layer 14, the n + region 13 and the Al electrode 15 are each about 1 μm.

  The p + region 12 has a thickness of about 1 μm, a width of 10 to 300 μm, a length of 20 to 50 mm, and is arranged in a striped pattern of about several tens to 1000 at a pitch of 20 to 500 μm. Since X-rays can be detected in each p + region 12, the X-ray detection semiconductor 10 has a large number of X-ray detection elements 17 (17A, 17B) having a thickness of 200 to 600 μm, a width of 20 to 500 μm, and a length of 30 to 50 mm. , 17C) are arranged in a one-dimensional manner orthogonal to the X-ray incident direction. Therefore, the X-ray detection element 17 becomes a pixel, and an X-ray image can be drawn thereby.

  The length of the p + region 12 can be 2 to 150 mm, but in the present invention, it is preferably 20 to 50 mm as described above. This length corresponds to 2 to 4 times the X-ray absorption length of the silicon-type semiconductor, and is a length capable of capturing most of the X-rays incident on the X-ray detection semiconductor 10. is there.

  The X-ray blocking member 20 includes a metal plate 21 and insulating layers 23 and 25 provided on both surfaces thereof, and has a structure in which the metal plate 21 is sandwiched between insulating materials. The metal plate 21 prevents the scattered X-rays scattered in the subject from entering the X-ray detection element 17, and other X-rays in which the scattered X-rays generated in the X-ray detection element 17 are stacked vertically. It has a collimator function that prevents it from reaching the line detection semiconductor 10. For this reason, the metal plate 21 preferably has a large atomic number and density, and preferably has good workability. For example, silver having an atomic number of 47 to lead having an atomic number of 82 or an alloy thereof is preferable. Also, platinum or gold deposited on the metal plate 21 is excellent as the X-ray blocking member 20 because X-rays are efficiently totally reflected.

  The insulating layers 23 and 25 are sufficient if they have a function of preventing the metal plate 21 and the X-ray detection semiconductor 10 from being energized, and the thinner the better. For example, a Kapton film or a metal oxide film having a thickness of 10 μm or less can be used. The insulating layers 23 and 25 may be formed integrally with the X-ray detection semiconductor 10.

  As shown in FIG. 3A, the X-ray blocking member 20 is preferably projected 20 to 40 mm in the X-ray incident direction side from the X-ray detection element 100 (L = 20 to 40 mm). Thereby, it is possible to effectively prevent the scattered X-rays scattered in the subject from entering the X-ray detection element 100. That is, the maximum aperture angle representing the removal rate of scattered X-rays can be set to 1 ° or less in the case of the present X-ray detection element 100 as shown below, and the removal of scattered X-rays compared to the conventional one. The X-ray detection element 100 having a considerably high rate and high sensitivity can be configured.

When the maximum opening angle α is the amount L of protrusion of the X-ray blocking member 20 from the X-ray detection element 100 and the inner width between the X-ray blocking members 20 is S, as shown in FIG. = Tan ^-1 (S / L). However, the substantial maximum opening angle α ₁ of the X-ray detection element 100 according to the present invention is α ₁ = tan ⁻¹ (S / L) considering that the X-ray absorption length of the silicon-type semiconductor is 5 to 15 mm. ₁ ). In the case of the present X-ray detection element 100, for example, if L = 20 mm, L ₁ = 30 mm, and S = 0.4 mm, α = 1.1 ° and α ₁ = 0.8 °. Incidentally, Patent Document 1 shows an example in which the maximum opening angle α is 3.4 °.

  The thickness T of the metal plate 21 of the X-ray blocking member 20 is preferably 40-100 μm. The plate thickness portion is preferably as thin as possible because it becomes a dead area where the X-ray transmitted through the subject is not detected by the X-ray detection element 100. However, for practical use, it is necessary to ensure the strength, so the thickness of the metal plate 21 is preferably 40 to 100 μm.

  As shown in FIG. 3B, the insensitive area can be reduced by providing inclined surfaces with an inclination angle θ = 0.05 to 0.1 ° on both ends of the X-ray blocking member 20. That is, among the transmitted X-rays from the subject, those that hit the inclined surface at the end of the X-ray blocking member 20 as shown in FIG. 3B can be totally reflected and guided to the X-ray detection element 17. This is because the transmission X-ray detection range is widened. With the above configuration, the sensitivity of the X-ray detection element 100 can be further improved.

  As described above, in the present X-ray detection element 100, the X-ray blocking member 20 has a collimator function, the X-ray detection semiconductor 10 has an X-ray detection function, and serves as an intermediate material (support material) of the collimator. It has a function. That is, the X-ray detection element 100 functions as a compact X-ray detector with a collimator having a simple structure.

  By using the X-ray detection element 100 described above, an X-ray detection apparatus as shown in FIGS. 1 and 4 can be configured. The X-ray detection apparatus 300 includes the X-ray detection element 100, a bias application unit 110 that applies a bias voltage to the X-ray detection element 100, and a reading unit 200 that reads a signal from the X-ray detection element 100 via wiring. It has.

As shown in FIG. 1, the bias application unit 110 includes a power source 111 and a bias resistor 112 so that a bias voltage can be applied to the X-ray detection element 100 through the p + region 12 and the Al electrode 15 of the X-ray detection element 17. It has become. In the case of this example, a reverse bias voltage of 50 to 150 V is applied. If the bias voltage V (volt) is the thickness D (μm) of the X-ray detection element 17 and the resistivity ρ (Ωcm), when the X-ray detection element 17 is made of a silicon n-type semiconductor substrate, V = ( (D / 0.53) ² × (1 / ρ) When the X-ray detection element 17 is made of a silicon p-type semiconductor substrate, V = ((D / 0.32) ² × (1 / ρ) According to this, when the X-ray detection element 17 is made of a silicon n-type semiconductor substrate with a thickness of 410 μm, and D = 410 μm and ρ = 10 kΩcm, the bias voltage V is about 60V.

  The reading unit 200 has a preamplifier 202 that amplifies the signal from the X-ray detection element 100, a shaper 204 that shapes the waveform of the amplified signal, and an input of a signal having a certain strength or more to the X-ray detection element 100. In this case, a comparator 206 for outputting a digital signal, a counter 208 for counting the digital signal, and an interface 220 for inputting a signal from the counter 208 to a computer 230 for outputting the image as an image are provided.

  Thus, the above-described X-ray detection element 100 is an X-ray detector with a collimator that can effectively prevent scattered X-rays with a simple structure, and uses a widely used silicon semiconductor manufacturing method. Can be created. Further, the X-ray detection apparatus 300 can obtain a clear X-ray image with high sensitivity. However, the X-ray detection element 100 and the X-ray detection apparatus 300 are not limited to the above-described embodiments. The X-ray detection semiconductor 10 only needs to be capable of detecting the intensity and amount of incident X-rays by directly detecting electron-hole pairs generated by X-ray photons. For example, X-ray detection The n + region 13 of the X-ray detection semiconductor 10 constituting the element 100 can be striped so as to face the p + region 12 as shown in FIG. Further, as shown in FIG. 5B, the p + region 12 and the n + region 13 can be arranged in a staggered manner. In this case, if the pitches of the p + region 12 and the n + region 13 are the same, two outputs based on electrons and holes can be used, and the X-ray detection sensitivity can be improved.

  Furthermore, the X-ray detection semiconductor 10 can be configured based on a silicon p-type semiconductor substrate. In this case, the X-ray detection semiconductor 10 is formed such that n + regions are arranged in stripes on one surface layer portion of a silicon p-type semiconductor substrate, and a p + region corresponding to the n + region is disposed on the other surface layer portion.

  When X-rays emitted from the point source are detected, as shown in FIG. 6A, the X-ray detection element 100 has a striped pattern formed by the p + region 12 of the X-ray detection semiconductor 10. It is preferable that the shape is divergent in the direction opposite to the X-ray incident direction. Further, as shown in FIG. 6 (b), the X-ray detection element 100 is preferably shaped so that the arrangement of the X-ray blocking members 20 is divergent. Thereby, scattered X-rays can be effectively eliminated.

  Furthermore, the reading unit of the X-ray detection apparatus can be configured as follows. That is, as shown in FIG. 7, the reading unit 201 can include a preamplifier 202, a shaper 204, a sample hold 211, a multiplexer 213, an A / D conversion device 215, an interface 220, and a computer 230. In this case, the signals from the X-ray detection element 100 once held in the sample hold 211 unit are read out in order by the multiplexer 213, and the read signals are A / D converted by the A / D converter 215 sequentially. Therefore, the economical X-ray detection apparatus 300 can be configured.

It is a figure which shows typically the cross section of the X-ray detection element which concerns on this invention. It is a top view of the X-ray detection semiconductor part of FIG. It is a figure which shows typically the cross section of the X-ray prevention member part of FIG. 1 is a layout diagram illustrating an X-ray detection apparatus according to the present invention. It is a schematic diagram which shows the other Example of an X-ray detection element. It is a schematic diagram which shows the other Example of an X-ray detection element. It is a layout figure which shows the other Example of an X-ray detection apparatus.

Explanation of symbols

10 X-ray detection semiconductor
11 Depletion layer
12 p + region
13 n + region
14 SiO ₂ layer
15 Al electrode
17 (17A, 17B, 17C) X-ray detector
20 X-ray blocking member
21 Metal plate
23 Insulation layer
25 Insulation layer
30 X-rays from a point source
100 X-ray detection element
110 Bias application section
111 Power supply
112 Bias resistor
200, 201 reading section
202 preamplifier
204 shaper
206 Comparator
208 counter
211 Sample hold
213 multiplexer
215 A / D converter
220 interface
230 computers
300 X-ray detector

Claims (9)

  An X-ray detection element formed by alternately stacking X-ray detection semiconductors having a large number of X-ray detection elements arranged one-dimensionally and X-ray blocking members.   A number of one-dimensionally arranged X-ray detection elements are formed by arranging p + regions in a striped pattern on one surface layer of a silicon n-type semiconductor substrate and arranging n + regions corresponding to the p + region on the other surface layer. The X-ray detection element according to claim 1, wherein   A number of one-dimensionally arranged X-ray detection elements are formed by arranging n + regions in a striped pattern on one surface layer portion of a silicon p-type semiconductor substrate and arranging a p + region corresponding to the n + region on the other surface layer portion. The X-ray detection element according to claim 1, wherein   The X-ray detection element according to claim 1, wherein the X-ray detection element is configured to receive emitted X-rays in a longitudinal direction of a striped p + or n + region.   The X-ray detection element according to claim 1, wherein the length of the striped p + or n + region of the X-ray detection element in the longitudinal direction is 20 to 50 mm.   The X-ray detection element according to any one of claims 1 to 5, wherein the X-ray blocking member has a protruding amount from the X-ray detection element of 20 to 40 mm.   The X-ray detection element according to claim 1, wherein the X-ray blocking member has a plate thickness of 40 to 100 μm.   The X-ray detection element according to claim 6 or 7, wherein the X-ray blocking member is provided with inclined surfaces having an inclination angle of 0.05 to 0.1 ° on both ends of the X-ray blocking member.   The X-ray detection element according to any one of claims 1 to 8, a bias application unit that applies a bias voltage to the X-ray detection element, and a reading unit that reads a signal from the X-ray detection element via a wiring; X-ray detection apparatus.

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