Radiation detector and radiation detection apparatus

Abstract

To provide a radiation detector capable of improving the energy resolution of a plurality of pixel electrodes located at the peripheral part of a radiation detector in a multichannel-type radiation detector.SOLUTION: A radiation detector includes: a first part including, in this order, a first electrode part, a semiconductor crystal part, and a second electrode part facing the first electrode portion; and a second part provided so as to surround a side surface of the semiconductor crystal part. The second part includes, in this order from the side surface of the semiconductor crystal part, an insulating layer and a conductive layer, and the second electrode part includes a plurality of pixel electrodes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a radiation detector and a radiation detection apparatus. [Background technology]

[0002] Conventionally, radiation detection devices for detecting radiation have been known. For example, a multi-channel radiation detection device is known, which includes a radiation detector having a common electrode for bias supply, multiple pixel electrodes for signal extraction, and a semiconductor crystal. In a multi-channel radiation detection device, when a voltage is applied between the common electrode and the multiple pixel electrodes, radiation is incident on and interacts with the semiconductor crystal that constitutes the radiation detector, generating electrons and holes in the semiconductor crystal. The number of generated electrons and holes increases according to the intensity of the incident radiation. The electrons and holes are each accelerated by the voltage applied to the semiconductor crystal and detected as a current. A radiation spectrum (energy spectrum) can be obtained from the magnitude of the detected current. For example, a semiconductor radiation detector described in Patent Document 1 is known as a radiation detector having multiple pixel electrodes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-92806 Summary of the Invention [Problem to be solved by the invention]

[0004] Radiation detection devices are required to have radiation detectors with high energy resolution. The narrower the half-width of the peaks appearing in the energy spectrum, the better the energy resolution of the radiation detector. As a result of extensive research, the present inventors have found that, among the multiple pixel electrodes in a multi-channel radiation detector, the multiple pixel electrodes located on the periphery of the radiation detector tend to have lower energy resolution than the multiple pixel electrodes located in the center of the radiation detector.

[0005] Therefore, an object of one aspect of the present invention is to provide a radiation detector that can improve the energy resolution of a plurality of pixel electrodes located on the periphery of a multi-channel radiation detector, and an object of another aspect of the present invention is to provide a radiation detection device that includes the radiation detector. [Means for solving the problem]

[0006] The present invention includes, for example, the following [1] to

[16] . [1] A first portion including, in this order, a first electrode portion, a semiconductor crystal portion, and a second electrode portion facing the first electrode portion; a second portion provided to surround a side surface of the semiconductor crystal portion; Equipped with the second portion has an insulating layer and a conductive layer in this order from a side surface of the semiconductor crystal portion, The radiation detector, wherein the second electrode portion has a plurality of pixel electrodes. [2] The radiation detector according to [1], wherein the semiconductor crystal portion has a semiconductor crystal containing at least one selected from the group consisting of thallium bromide, cadmium telluride, cadmium zinc telluride, and cesium lead tribromide. [3] The radiation detector according to [1] or [2], wherein the semiconductor crystal portion is composed of a plurality of semiconductor crystals. [4] The radiation detector according to any one of [1] to [3], wherein the insulating layer is disposed so as to cover the entire side surface of the semiconductor crystal portion. [5] The radiation detector according to any one of [1] to [4], wherein the insulating layer protrudes toward the first electrode portion with respect to a plane including the surface of the semiconductor crystal portion on the first electrode portion side. [6] The radiation detector according to any one of [1] to [5], wherein the insulating layer contains at least one resin selected from the group consisting of silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluororesin. [7] The radiation detector according to any one of [1] to [6], wherein the insulating layer has a dielectric strength of 1.5 kV / mm or more in the thickness direction. [8] The radiation detector according to any one of [1] to [7], wherein the insulating layer has a dielectric strength of 19 kV / mm or more in the thickness direction. [9] The radiation detector according to any one of [1] to [8], wherein the insulating layer has a thickness of 150 μm or less.

[10] The radiation detector according to any one of [1] to [9], wherein the insulating layer has a thickness of 50 μm or less.

[11] The radiation detector according to any one of [1] to

[10] , wherein the conductive layer contains at least one selected from the group consisting of copper, aluminum, gold, and alloys containing these elements.

[12] The radiation detector according to any one of [1] to

[11] , wherein the conductive layer has a thickness of 50 nm or more.

[13] The radiation detector according to any one of [1] to

[12] , wherein the conductive layer has a thickness of 150 nm or more.

[14] The radiation detector according to any one of [1] to

[13] , wherein the second portion includes the insulating layer and the conductive layer in this order from a side surface of the first electrode portion.

[15] Further comprising a circuit unit electrically connected to each of the plurality of pixel electrodes, The radiation detector according to any one of [1] to

[14] , wherein the circuit section processes information collected for each of the plurality of pixel electrodes and outputs the processed information as data.

[16] A radiation detector according to any one of [1] to

[15] ; a power source that applies a voltage to the radiation detector; a control unit electrically connected to the radiation detector and the power source; A radiation detection device comprising:

[17] The radiation detection device according to

[16] , wherein the potential of the conductive layer is in a floating state. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a radiation detector that can improve the energy resolution of a plurality of pixel electrodes located on the periphery of a multi-channel radiation detector, and also to provide a radiation detection device that includes the radiation detector. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an embodiment of a radiation detector. [Figure 2] FIG. 2 is a plan view of a plurality of pixel electrodes. [Figure 3] FIG. 3 is a plan view of the semiconductor crystal portion. [Figure 4] FIG. 4 is a graph showing the results of the energy spectrum at one corner point of the pixel electrodes of Example 1 and Comparative Example 1. [Figure 5] FIG. 5 is a graph showing the tendency of the average values ​​of FWHM for Examples 1 to 4 and Comparative Example 1. [Figure 6] FIG. 6 is a graph showing the relationship between the thickness of the conductive layer and the average value of the FWHM. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0010] In this specification, "multiple pixel electrodes located in the peripheral portion" refers to pixel electrodes arranged along the periphery of the electrode portion in a plan view of the electrode portion where the multiple pixel electrodes are present. Also, in this specification, "multiple pixel electrodes located in the central portion" refers to pixel electrodes arranged within an area that is half the length from the center to the periphery of the electrode portion in a plan view of the electrode portion where the multiple pixel electrodes are present.

[0011] 1 is a schematic cross-sectional view showing one embodiment of a radiation detector. Radiation detector 100 (hereinafter also simply referred to as "detector 100") is a flat-plate detector including a first electrode portion 11, a second electrode portion 12, a semiconductor crystal portion 13, an insulating portion 14, a connecting portion 15, a circuit board 16, a protective layer 17, an insulating layer 21, and a conductive layer 22. Semiconductor crystal portion 13 has two parallel surfaces, with first electrode portion 11 formed on one of these surfaces and second electrode portion 12 formed on the other surface.

[0012] The detector 100 includes a first portion 10 having, in the X direction, a protective layer 17, a first electrode portion 11, a semiconductor crystal portion 13, a second electrode portion 12, a connection portion 15, and a circuit board 16, in this order. In the X direction, the first electrode portion 11 and the second electrode portion 12 face each other with the semiconductor crystal portion 13 interposed therebetween. The radiation detector does not need to include at least one selected from the group consisting of a protective layer, a connection portion, and a circuit board. That is, the first portion of the radiation detector has at least a first electrode portion, a semiconductor crystal portion, and a second electrode portion, in this order.

[0013] The detector 100 includes a second portion 20 provided to surround a side surface 13SY (a surface parallel to the X direction) of the semiconductor crystal portion 13. The second portion 20 has an insulating layer 21 and a conductive layer 22, in this order, from the side surface 13SY of the semiconductor crystal portion 13 in directions perpendicular to the X direction (Y direction and Z direction). The entire side surface of the first electrode portion 11 of the detector 100 is covered with the insulating layer 21, and the second portion 20 of the detector 100 has the insulating layer 21 and the conductive layer 22, in this order, from the side surface of the first electrode portion 11 in the direction perpendicular to the X direction. The first electrode portion does not have to be covered with an insulating layer, and the second portion does not have to have the insulating layer and the conductive layer, in this order, from the side surface of the first electrode portion.

[0014] One of the first electrode portion 11 and the second electrode portion 12 corresponds to an anode electrode, and the other corresponds to a cathode electrode. For example, when the first electrode portion 11 is a cathode electrode, the second electrode portion 12 is an anode electrode.

[0015] The electrodes in the first electrode unit 11 and the second electrode unit 12 may have a metal layer containing at least one selected from the group consisting of metals such as copper, gold, platinum, silver, thallium, nickel, and indium, and alloys containing these elements, and an underlayer containing at least one selected from the group consisting of metals such as chromium, nickel, and bismuth, and alloys containing these elements. The thickness of the underlayer is, for example, 10 nm to 900 nm. The electrodes in the first electrode unit 11 and the second electrode unit 12 may have a low-resistance metal layer made of a metal having a lower resistivity than the metal layer, provided on the semiconductor crystal unit 13 side. The low-resistance metal layer may be, for example, a gold layer. The thickness of the low-resistance metal layer is, for example, 10 nm to 900 nm. An intermediate layer containing a metal such as chromium, nickel, or bismuth may be further provided between the low-resistance metal layer and the metal layer to enhance adhesion between them. The thickness of the intermediate layer is, for example, 1 nm to 900 nm. The underlayer, the low-resistance metal layer, and the intermediate layer may be vapor-deposited metal films. The electrodes in the first electrode portion 11 and the second electrode portion 12 may have, for example, the following laminated structure. Metal layer / low resistance metal layer Metal layer / intermediate layer / low resistance metal layer Base layer / metal layer Base layer / metal layer / low resistance metal layer Base layer / metal layer / intermediate layer / low resistance metal layer

[0016] The first electrode unit 11 has one electrode (common electrode). The electrode in the first electrode unit 11 is electrically connected to a power source. When the first electrode unit 11 corresponds to a cathode electrode, the first electrode unit 11 collects carriers (holes) generated by the interaction between the incident radiation and the semiconductor crystal unit 13. When the first electrode unit 11 is a cathode electrode, a voltage of -50 to -1000 V may be applied to the electrode of the first electrode unit.

[0017] The first electrode portion 11 is rectangular (square, oblong) in plan view when viewed from the X direction. The lengths of the first electrode portion 11 in the Y direction and the Z direction may each be, for example, 10 to 50 mm. The thickness (length in the X direction) of the first electrode portion 11 may be, for example, 10 to 10,000 nm.

[0018] 2, the second electrode unit 12 has a plurality of pixel electrodes 12E and an insulating unit 14. The plurality of pixel electrodes 12E are arranged in the Y direction and the Z direction. The second electrode unit 12 has a plurality of pixel electrodes 12E, which can improve the energy resolution.

[0019] When the second electrode portion 12 is an anode electrode, that is, when the pixel electrode 12E is an anode electrode, the second electrode portion 12 collects carriers (electrons) generated by the interaction between the incident radiation and the semiconductor crystal portion 13.

[0020] The first electrode portion 11 and the second electrode portion 12 face each other. All of the plurality of pixel electrodes 12E face the first electrode portion 11 via the semiconductor crystal portion 13. It is sufficient that at least one electrode of the plurality of pixel electrodes faces the first electrode portion.

[0021] The second electrode portion 12 has a rectangular shape (square or oblong) when viewed from above in the X direction.

[0022] Each of the plurality of pixel electrodes 12E has a rectangular shape (square or oblong) when viewed from above in the X direction.

[0023] The insulating portion 14 is provided to prevent electrical interference between adjacent pixel electrodes 12E. Examples of resins that can form the insulating portion 14 include resin materials such as silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluororesin; and inorganic insulating materials such as silicon oxide, silicon nitride, and aluminum oxide. From the perspective of sufficiently preventing electrical interference between adjacent pixel electrodes 12E, the insulating portion 14 may contain at least one material selected from the group consisting of silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluororesin. The insulating portion 14 may be formed by a gap (air) rather than by providing a member.

[0024] The semiconductor crystal portion 13 is composed of a semiconductor crystal that generates electrons and holes (carriers) by interacting with incident radiation (X-rays, gamma rays, etc.). That is, the semiconductor crystal portion 13 is composed of a crystal containing a substance (compound semiconductor) that generates carriers by interacting with incident radiation. From the viewpoint of achieving superior radiation absorption efficiency, the semiconductor crystal portion 13 may have a semiconductor crystal that contains at least one selected from the group consisting of thallium bromide, cadmium telluride, cadmium zinc telluride, and cesium lead tribromide, and in particular may have a semiconductor crystal that contains thallium bromide.

[0025] From the viewpoint of excellent radiation absorption efficiency, the content of thallium bromide in the semiconductor crystal of the semiconductor crystal portion 13 may be 80 mass% or more, 90 mass% or more, 95 mass% or more, or 98 mass% or more, based on the total mass of the semiconductor crystal, or may be substantially 100 mass% (an embodiment in which the semiconductor crystal consists of thallium bromide).

[0026] The thickness (length in the X direction) of the semiconductor crystal portion 13 may be, for example, 0.5 to 10 mm.

[0027] Semiconductor crystal portion 13 may be composed of a single semiconductor crystal, or may be composed of multiple semiconductor crystals in order to increase the detection area. That is, the radiation detector may include a semiconductor crystal portion having one semiconductor crystal for one second electrode portion, or may include a semiconductor crystal portion having multiple semiconductor crystals for one second electrode portion. When the semiconductor crystal portion is composed of multiple semiconductor crystals, the number of semiconductor crystals is not particularly limited, and the semiconductor crystal portion may be composed of, for example, four semiconductor crystals or nine semiconductor crystals.

[0028] A plan view of the semiconductor crystal portion 13 made up of multiple semiconductor crystals is shown in Fig. 3. In Fig. 3, the semiconductor crystal portion has four semiconductor crystals 13A and a resin layer 18. The resin layer 18 is provided at the interface between the semiconductor crystals 13A and bonds the semiconductor crystals 13A together.

[0029] The four semiconductor crystals 13A each have approximately the same composition, and examples of materials that constitute the semiconductor crystals 13A include thallium bromide, cadmium telluride, cadmium zinc telluride, cesium lead tribromide, etc. The thicknesses (lengths in the X direction) of the four semiconductor crystals 13A are approximately the same, and may be within the thickness range of the semiconductor crystal portion 13 described above.

[0030] The resin layer 18 is formed of, for example, silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, fluororesin, or the like. The resin layer 18 may be formed of, for example, humiseal manufactured by Air Brown Co., Ltd. The thickness (length in the X direction) of the resin layer 18 may be approximately the same as the thickness of the semiconductor crystals 13A. The width (length between the semiconductor crystals 13A; length in the Y direction or Z direction) of the resin layer 18 may be, for example, 0.01 to 1 mm.

[0031] The connection portions 15 electrically connect each of the plurality of pixel electrodes 12E of the second electrode portion 12 to a circuit board 16, which will be described later. The connection portions 15 are made of a conductive material, such as solder or a conductive adhesive.

[0032] The circuit board (circuit section) 16 has a wiring pattern connected to the connection section 15 and a signal processing circuit. Examples of materials for the circuit board 16 include silicon, ceramic, quartz, glass, and plastic. Examples of materials that can be used for the circuit board 16 include a glass composite substrate (CEM-3) made by impregnating a substrate of glass cloth and nonwoven glass cloth with epoxy resin, a glass epoxy substrate (FR-4) made by impregnating a layer of glass fiber cloth with epoxy resin, and a metal heat dissipation substrate made of copper, aluminum, or the like. The signal processing circuit is, for example, an ASIC (Application Specific Integrated Circuit). The signal processing circuit processes carrier information (current value information) collected for each of the multiple pixel electrodes 12E and outputs the processed information to the control unit as radiation image data. The signal processing circuit continuously or intermittently outputs the radiation image data to the control unit. The radiation image data may be the radiation image itself or data for generating the radiation image. The signal processing circuit may be provided on a substrate separate from the circuit board 16.

[0033] The protective layer 17 protects the first electrode unit 11. The protective layer may be provided to protect not only the first electrode unit but also the second electrode unit, the conductive layer, the insulating layer, the substrate, and the like.

[0034] The protective layer 17 may be formed of, for example, an insulating material, such as a resin material including silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluororesin; or an insulating inorganic material including silicon oxide, silicon nitride, and aluminum oxide.

[0035] The thickness (length in the X direction) of the protective layer 17 may be, for example, 0.1 to 2.0 mm. When the thickness of the protective layer 17 is 0.5 mm or more, the first electrode portion 11 can be sufficiently protected.

[0036] The insulating layer 21 is provided to surround the side surface 13SY of the semiconductor crystal portion 13 and electrically insulates the semiconductor crystal portion 13 from the conductive layer 22. The insulating layer 21 may cover at least a portion of the side surface 13SY of the semiconductor crystal portion 13, or may be formed to cover the entire side surface 13SY of the semiconductor crystal portion 13 from the viewpoint of further improving the energy resolution of the multiple pixel electrodes 12E located in the peripheral portion and facilitating uniform detection characteristics among the multiple pixel electrodes 12E. As shown in FIG. 3 , when the semiconductor crystal portion is composed of multiple semiconductor crystals 13A, the insulating layer 21 is provided to surround the side surface of the semiconductor crystal portion composed of the multiple semiconductor crystals 13A, rather than the side surface of each semiconductor crystal 13A. The insulating layer 21 may be formed not only on the side surface 13SY of the semiconductor crystal portion 13 but also on the side surfaces of the first electrode portion 11 and / or the second electrode portion 12.

[0037] Insulating layer 21 protrudes toward first electrode 11 with respect to a plane including surface 13SX of semiconductor crystal portion 13 on the first electrode portion 11 side. By having insulating layer 21 protrude toward first electrode 11 with respect to a plane including surface 13SX of semiconductor crystal portion 13 on the first electrode portion 11 side, it is possible to reliably prevent short-circuiting (discharge) between the electrode of first electrode portion 11 and conductive layer 22. Furthermore, when protective layer 17 is provided on first electrode portion 11, because insulating layer 21 protrudes toward first electrode 11 with respect to a plane including surface 13SX of semiconductor crystal portion 13 on the first electrode portion 11 side, if protective layer 17 is formed of a liquid material, the protruding portion of insulating layer 21 prevents the material forming protective layer 17 from flowing out onto side surface 13SY of semiconductor crystal portion 13, making it easier to arrange multiple radiation detectors adjacent to each other. Insulating layer 21 may protrude by 1 mm or more, or may protrude by more than 0 mm and less than 1 mm, from a plane including surface 13SX on the first electrode portion 11 side of semiconductor crystal portion 13. The insulating layer does not have to protrude toward the first electrode portion side from a plane including the surface on the first electrode portion side of the semiconductor crystal portion.

[0038] The insulating layer 21 is formed of an insulating material. From the viewpoint of ensuring sufficient insulation, examples of materials for forming the insulating layer 21 include resin materials such as silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluororesin; and inorganic materials having insulation properties such as silicon oxide, silicon nitride, and aluminum oxide. The insulating layer 21 may be formed of voids (air). From the viewpoint of ensuring even more sufficient insulation, the insulating layer 21 may contain at least one material selected from the group consisting of silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluororesin.

[0039] From the viewpoint of ensuring sufficient insulation, the dielectric strength of insulating layer 21 in the thickness direction may be, for example, 1 kV / mm or more, 1.5 kV / mm or more, 5 kV / mm or more, 10 kV / mm or more, 15 kV / mm or more, 19 kV / mm or more, or 25 kV / mm or more. The upper limit of the dielectric strength of insulating layer 21 in the thickness direction is not particularly limited, and may be, for example, 1000 kV / mm or less or 500 kV / mm or less.

[0040] From the viewpoint of ensuring sufficient insulation, the withstand voltage of insulating layer 21 in the thickness direction (direction perpendicular to the X direction) may be 0.01 kV or more, 0.1 kV or more, 0.5 kV or more, 0.9 kV or more, 1 kV or more, 2 kV or more, 4 kV or more, or 5 kV or more. The withstand voltage of insulating layer 21 in the thickness direction may be 20 kV or less, 15 kV or less, 10 kV or less, 8 kV or less, or 7 kV or less. The withstand voltage of insulating layer 21 can be calculated by multiplying the dielectric strength in the thickness direction of insulating layer 21 by the thickness of insulating layer 21.

[0041] The thickness of the insulating layer 21 (the length in the direction perpendicular to the X direction) may be 300 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, 80 μm or less, 50 μm or less, or 35 μm or less, from the viewpoint of further improving the energy resolution of the plurality of pixel electrodes 12E located in the peripheral portion and from the viewpoint of easily uniforming the detection characteristics of each of the plurality of pixel electrodes 12E. The thickness of the insulating layer 21 may be 10 μm or more, 20 μm or more, or 30 μm or more, from the viewpoint of ensuring sufficient insulation. From these viewpoints, the thickness of the insulating layer 21 may be 10 to 300 μm, 20 to 200 μm, or 30 to 150 μm.

[0042] The conductive layer 22 is formed on the entire surface of the insulating layer 21. It is presumed that the presence of the conductive layer 22 in the detector 100 makes the electric field strength uniform in the outer periphery of the detector 100, thereby improving the energy resolution of the plurality of pixel electrodes 12E located in the outer periphery. The conductive layer may be formed on a portion of the surface of the insulating layer.

[0043] The conductive layer 22 is formed of a material having sufficient conductivity. To ensure sufficient conductivity, materials for forming the conductive layer 22 include, for example, metals such as copper, gold, platinum, silver, nickel, and indium, and metal materials such as alloys containing these elements; and carbon-containing materials such as carbon and conductive polymers. To improve the energy resolution of the multiple pixel electrodes 12E located in the peripheral portion, the conductive layer 22 may contain at least one metal selected from the group consisting of copper, aluminum, gold, and alloys containing these elements.

[0044] The potential of the conductive layer 22 may be in a floating state. By making the potential of the conductive layer 22 in a floating state, the energy resolution of the plurality of pixel electrodes 12E located in the peripheral portion can be further improved, and the detection characteristics of each of the plurality of pixel electrodes 12E can be made uniform. The conductive layer 22 may be applied with a potential in a non-floating state, or may be at ground potential.

[0045] The conductive layer 22 may be formed directly on the surface of the insulating layer 21 by vapor deposition or the like, or may be formed via an adhesive layer or the like. When the conductive layer 22 is formed on the surface of the insulating layer 21 via an adhesive layer, the conductive layer 22 may be formed on the surface of the insulating layer 21 using, for example, a conductive tape.

[0046] The conductive layer 22 protrudes toward the first electrode portion 11 from a plane including the surface 13SX of the semiconductor crystal portion 13 on the first electrode portion 11 side. The conductive layer 22 may protrude by 1 mm or more from a plane including the surface 13SX of the semiconductor crystal portion 13 on the first electrode portion 11 side, or may protrude by more than 0 mm but less than 1 mm. From the viewpoint of reliably suppressing short-circuiting (discharge) between the electrode of the first electrode portion and the conductive layer, the conductive layer does not have to protrude toward the first electrode portion from a plane including the surface of the semiconductor crystal portion on the first electrode portion side. From the viewpoint of reliably uniforming the electric field distribution within the semiconductor crystal portion, the conductive layer is preferably formed at least to a position flush with the plane including the surface 13SX of the semiconductor crystal portion on the first electrode portion side. Furthermore, from the viewpoint of reliably suppressing short-circuiting between the electrode of the first electrode portion and the conductive layer, the conductive layer is preferably formed at a position that is not flush with the plane including the surface 13SX of the semiconductor crystal portion on the first electrode portion side (i.e., the conductive layer is formed in a state where it protrudes or does not protrude from the first electrode).

[0047] The thickness of the conductive layer 22 (the length in the direction perpendicular to the X direction) may be 10 nm or more, 30 nm or more, 50 nm or more, 75 nm or more, 100 nm or more, or 150 nm or more from the viewpoint of further improving the energy resolution of the pixel electrodes 12E located in the peripheral portion and from the viewpoint of easily uniforming the detection characteristics of each of the pixel electrodes 12E. From the viewpoint of further improving the energy resolution of the pixel electrodes 12E located in the peripheral portion, the thickness of the conductive layer 22 may be 200 nm or more, 300 nm or more, or 400 nm or more. To ensure sufficient conductivity, the thickness of the conductive layer 22 may be 1000 nm or less, 800 nm or less, 600 nm or less, or 500 nm or less. From these viewpoints, the thickness of the conductive layer 22 may be 10 to 1000 nm, 30 to 800 nm, or 50 to 600 nm.

[0048] Increasing the thickness of the conductive layer 22 may result in the plurality of pixel electrodes 12E located on the periphery being superior in terms of energy resolution to those located in the center. This is presumably because, when the electric field strength is the same between the plurality of pixel electrodes 12E located on the periphery and the plurality of pixel electrodes 12E located in the center, the plurality of pixel electrodes 12E located on the periphery have fewer adjacent pixel electrodes and are therefore less susceptible to noise from the surrounding pixel electrodes.

[0049] The above-described radiation detector can be used in radiation detection devices, and more specifically, can be used in SPECT (Single Photon Emission Computed Tomography) devices, PET (Positron Emission Tomography) devices, gamma cameras, Compton cameras, imaging spectrometers, etc.

[0050] The radiation detector described above can improve the energy resolution of the multiple pixel electrodes 12E located in the peripheral region. The inventors speculate that this is because the distribution of the electric field formed inside the semiconductor crystal portion 13 by the potential difference between the first electrode portion 11 and the second electrode portion 12 is disturbed along the peripheral region of the semiconductor crystal portion 13. Specifically, they speculate that an equipotential surface parallel to one surface (the YZ plane) of the semiconductor crystal portion 13 is formed in the central region, resulting in a uniform electric field distribution. However, near the peripheral region of the semiconductor crystal portion 13, the equipotential surface distorts outward, resulting in a non-uniform electric field distribution. As a result of the non-uniform electric field distribution at the peripheral region of the semiconductor crystal portion 13, even if carriers are generated within the semiconductor crystal portion 13 by incident radiation, the collection efficiency of the multiple pixel electrodes 12E located in the peripheral region is reduced, resulting in a lower energy resolution than at the central region. Meanwhile, providing the insulating layer 21 and the conductive layer 22, in this order, on the side surfaces of the radiation detection element suppresses the distortion of the electric field near the peripheral region of the semiconductor crystal portion 13. Therefore, since the electric field formed inside the semiconductor crystal portion 13 becomes uniform, it is presumed that the decrease in carrier collection efficiency in the multiple pixel electrodes 12E located in the peripheral portion can be suppressed, and the energy resolution of the multiple pixel electrodes 12E located in the peripheral portion can be improved.

[0051] Furthermore, according to the radiation detector described above, the energy resolution of the pixel electrodes 12E located on the periphery is improved, thereby improving the energy resolution of the multi-channel detector as a whole. Furthermore, according to the radiation detector described above, the energy resolution of each pixel electrode is uniform, so that when applied to multiple simultaneous imaging that simultaneously measures radiation of different energies, high-precision imaging is possible.

[0052] When the radiation detector is used in a radiation detection apparatus, the radiation detection apparatus includes, in addition to the radiation detector, a power supply that applies a voltage to the radiation detector, and a control unit electrically connected to the radiation detector and the power supply. That is, another embodiment of the present invention is a radiation detection apparatus including the above-mentioned radiation detector, a power supply that applies a voltage to the radiation detector, and a control unit electrically connected to the radiation detector and the power supply.

[0053] In the radiation detection device, the power supply applies a voltage to the radiation detector in response to a control signal from the control unit. The power supply applies, for example, a high voltage (HV) to the radiation detector. The voltage (ON voltage value) applied by the power supply to the radiation detector may be set arbitrarily, for example, to a value between -50 and -1000V.

[0054] The control unit is electrically connected to the radiation detector and the power supply. The control unit is configured, for example, by an FPGA (Field-Programmable Gate Array). The control unit acquires radiation image data output from the radiation detector and outputs the radiation image data to the control device via the input / output interface. The control unit may generate a radiation image based on the acquired radiation image data. [Example]

[0055] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0056] Example 1 A laminate was fabricated, consisting of a 20mm x 20mm x 300nm thick common electrode made of a thallium alloy, a 3mm thick thallium bromide crystal (semiconductor crystal), a 20mm x 20mm x 3mm thick pixel electrode made of a thallium alloy (8x8 pixels), and a circuit board including an ASIC, in that order.

[0057] A 150 μm thick polyimide resin layer (Kapton tape, manufactured by DuPont-Toray Co., Ltd., dielectric strength: 380 kV / mm) was formed as an insulating layer to cover the entire side of the thallium bromide crystal of the fabricated laminate. At this time, the insulating layer protruded 0.5 mm from the plane including the surface of the thallium bromide crystal on the common electrode side. Next, a 0.3 μm thick gold layer was formed as a conductive layer by vapor deposition on the surface of the polyimide resin layer, and a radiation detector was obtained. At this time, the formed gold layer was in a floating state.

[0058] Example 2 A radiation detector was obtained in the same manner as in Example 1, except that the thickness of the polyimide resin layer was changed to 80 μm.

[0059] Example 3 A radiation detector was obtained in the same manner as in Example 1, except that the thickness of the polyimide resin layer was changed to 50 μm.

[0060] Example 4 A radiation detector was obtained in the same manner as in Example 1, except that the thickness of the polyimide resin layer was changed to 35 μm.

[0061] (Comparative Example 1) A radiation detector was obtained in the same manner as in Example 1, except that the polyimide resin layer and the gold layer were not formed.

[0062] [evaluation] The energy spectrum results for one corner of the pixel electrodes of Example 1 and Comparative Example 1 are shown in Figure 4. For Examples 1 to 4 and Comparative Example 1, the average FWHM (Full-width at Half-Maximum) values ​​of 16 points in the center of the pixel electrode, the average FWHM values ​​of 28 points on the outer edge, and the average FWHM values ​​of four points on the corners are shown in Table 1 and Figure 5. The center of the pixel electrode consists of 16 pixel electrodes selected in descending order of distance from the center of the pixel electrode (region A in Figure 2), the outer edge of the pixel electrode consists of 28 pixel electrodes selected in descending order of distance from the center of the pixel electrode (region B in Figure 2), and the corner of the pixel electrode consists of four pixel electrodes selected in descending order of distance from the center of the pixel electrode (region C in Figure 2). A smaller average FWHM value indicates better energy resolution. Furthermore, the more similar (within ±1%) the average FWHM values ​​of the 16 central points, the 28 outer edge points, and the 4 corner points are, the more uniform the detection characteristics (energy resolution) of each of the multiple pixel electrodes are.

[0063] [Table 1]

[0064] Example 5 A radiation detector was obtained in the same manner as in Example 3, except that the insulating layer was formed so as to protrude 1.5 mm from a plane including the surface of the thallium bromide crystal on the common electrode side. The average FWHM value of 16 points in the center of the pixel electrode was 7.8%, the average FWHM value of 28 points on the outer edge was 7.4%, and the average FWHM value of 4 points at the corners was 7.4%.

[0065] Example 6 A radiation detector was obtained in the same manner as in Example 4, except that the insulating layer was formed so as to protrude 1.5 mm from a plane including the surface of the thallium bromide crystal on the common electrode side. The average FWHM value of 16 points in the center of the pixel electrode was 7.8%, the average FWHM value of 28 points on the outer edge was 7.0%, and the average FWHM value of 4 points at the corners was 7.0%.

[0066] (Examples 7 to 11, Comparative Examples 2 to 3) A radiation detector was obtained in the same manner as in Example 1, except that the insulating layer and conductive layer were changed as shown in Table 2. The insulating layer and insulating layer in the table indicate that they were formed from the materials shown below, and a "-" in the column for conductive layer in Table 2 indicates that no conductive layer was formed. In addition, in the evaluation column in Table 2, if the energy resolution of the outer periphery of the radiation detector (28 points on the outer edge and 4 points on the corners) was comparable to that of Example 1, it was marked with "A," if it was slightly inferior to Example 1 but better than Comparative Example 1, it was marked with "B," and if it was comparable to that of Comparative Example 1, it was marked with "C." Polyimide resin layer (Kapton tape manufactured by Toray DuPont Co., Ltd., thickness: 35 μm, dielectric strength: 380 kV / mm) Fluorine resin layer (Valqua Corporation, Valflon (registered trademark), thickness: 50 μm, dielectric strength: 19 kV / mm) Silicone resin layer (manufactured by Fuji Polymer Industries, thickness: 250 μm, dielectric strength: 26 kV / mm) Acrylic resin layer (Air Brown Co., Ltd., humiseal 1B66NS, thickness: 20 μm, dielectric strength: 22.4 kV / mm) Aluminum layer (formed by vapor deposition, thickness: 0.3 μm) Copper layer (Terada Manufacturing Co., Ltd., product name 8323, copper tape, thickness: 70 μm)

[0067] [Table 2]

[0068] Examples 12 to 14 A radiation detector was obtained in the same manner as in Example 7, except that the thickness of the aluminum layer was changed as shown in Table 3. The average FWHM values ​​of 16 points in the center of the pixel electrode, the average FWHM values ​​of 28 points on the outer edge, and the average FWHM values ​​of 4 points on the corners are shown in Table 3 and FIG.

[0069] [Table 3] [Explanation of symbols]

[0070] 10...first portion, 11...first electrode portion, 12...second electrode portion, 12E...pixel electrode, 13...semiconductor crystal portion, 13A...semiconductor crystal, 13SX...surface, 13SY...side, 14...insulating portion, 15...connecting portion, 16...circuit board, 17...protective layer, 18...resin layer, 20...second portion, 21...insulating layer, 22...conductive layer, 100...radiation detector.

Claims

1. a first portion including, in this order, a first electrode portion, a semiconductor crystal portion, and a second electrode portion facing the first electrode portion; a second portion provided to surround a side surface of the semiconductor crystal portion; Equipped with the second portion has an insulating layer and a conductive layer in this order from a side surface of the semiconductor crystal portion, The radiation detector, wherein the second electrode portion has a plurality of pixel electrodes.

2. 2. The radiation detector according to claim 1, wherein the semiconductor crystal portion has a semiconductor crystal containing at least one selected from the group consisting of thallium bromide, cadmium telluride, cadmium zinc telluride, and cesium lead tribromide.

3. The radiation detector according to claim 1 , wherein the semiconductor crystal portion is made up of a plurality of semiconductor crystals.

4. The radiation detector according to claim 1 , wherein the insulating layer is disposed so as to cover the entire side surface of the semiconductor crystal portion.

5. The radiation detector according to claim 1 , wherein the insulating layer protrudes toward the first electrode portion with respect to a plane including a surface of the semiconductor crystal portion on the first electrode portion side.

6. 2. The radiation detector according to claim 1, wherein the insulating layer contains at least one resin selected from the group consisting of a silicone resin, an acrylic resin, a polyurethane resin, a polyimide resin, a polyolefin resin, and a fluororesin.

7. 2. The radiation detector according to claim 1, wherein the insulating layer has a dielectric strength of 1.5 kV / mm or more in the thickness direction.

8. 2. The radiation detector according to claim 1, wherein the insulating layer has a dielectric strength of 19 kV / mm or more in the thickness direction.

9. The radiation detector according to claim 1 , wherein the insulating layer has a thickness of 150 μm or less.

10. 2. The radiation detector according to claim 1, wherein the insulating layer has a thickness of 50 [mu]m or less.

11. 2. The radiation detector according to claim 1, wherein the conductive layer contains at least one element selected from the group consisting of copper, aluminum, gold, and alloys containing these elements.

12. The radiation detector according to claim 1 , wherein the conductive layer has a thickness of 50 nm or more.

13. The radiation detector according to claim 1 , wherein the conductive layer has a thickness of 150 nm or more.

14. The radiation detector according to claim 1 , wherein the second portion includes the insulating layer and the conductive layer in this order from a side surface of the first electrode portion.

15. a circuit section electrically connected to each of the plurality of pixel electrodes; The radiation detector according to claim 1 , wherein the circuit section processes information collected for each of the plurality of pixel electrodes and outputs the processed information as data.

16. The radiation detector according to any one of claims 1 to 15, a power source that applies a voltage to the radiation detector; a control unit electrically connected to the radiation detector and the power source; A radiation detection device comprising:

17. The radiation detection device according to claim 16 , wherein the potential of the conductive layer is set to a floating state.

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