Radiation detector and radiation detection apparatus

Abstract

The present invention relates to a radiation detector including: a first portion including a first electrode portion, a semiconductor crystal portion, and a second electrode portion opposed to the first electrode portion in this order; and a second portion provided so as to surround a side surface of the semiconductor crystal portion, the second portion having an insulating layer and a conductive layer in this order from the side surface of the semiconductor crystal portion, and the second electrode portion having a plurality of pixel electrodes.

Description

TECHNICAL FIELD

[0001] The present application relates to a radiation detector and a radiation detection apparatus. BACKGROUND

[0002] Conventionally, a radiation detection apparatus that detects radiation is known. As the radiation detection apparatus, for example, a multi-channel type radiation detection apparatus including a radiation detector having a common electrode for bias supply, a plurality of pixel electrodes for signal extraction, and a semiconductor crystal is known. In the multi-channel type radiation detection apparatus, when radiation is incident to the semiconductor crystal constituting the radiation detector and interacts, electrons and holes are generated in the semiconductor crystal in a state where a voltage is applied between the common electrode and the plurality of pixel electrodes. The number of the generated electrons and holes increases in accordance with the intensity of the incident radiation. The electrons and holes are accelerated by the voltage applied to the semiconductor crystal and are detected as electric current. The radiation spectrum (energy spectrum) can be obtained from the magnitude of the detected electric current. As the radiation detector having the plurality of pixel electrodes, for example, a semiconductor radiation detector described in Patent Literature 1 is known.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 9-92806 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the radiation detection apparatus, a radiation detector having a high energy resolution is required. It can be said that the narrower the half-value width of the peak of the energy spectrum appears, the more excellent the energy resolution of the radiation detector is. As a result of diligent studies by the present inventors, it has been found that, in the multi-channel type radiation detector, there is a tendency that the energy resolution of the plurality of pixel electrodes located at the outer peripheral portion of the radiation detector deteriorates compared to the plurality of pixel electrodes located at the central portion of the radiation detector.

[0008] Therefore, an object of one aspect of the present application is to provide a radiation detector capable of improving the energy resolution of the plurality of pixel electrodes located at the outer peripheral portion of the radiation detector in the multi-channel type radiation detector. Further, an object of another aspect of the present application is to provide a radiation detection apparatus including the radiation detector.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] The present application includes, for example, [1] to

[17] below.

[0011] [1] A radiation detector comprising:

[0012] a first portion including, in order, a first electrode portion, a semiconductor crystal portion, and a second electrode portion opposite the first electrode portion; and

[0013] a second portion disposed in a manner surrounding a side surface of the semiconductor crystal portion,

[0014] the second portion having, in order from the side surface of the semiconductor crystal portion, an insulating layer and a conductive layer,

[0015] the second electrode portion having a plurality of pixel electrodes.

[0016] [2] The radiation detector according to [1], wherein:

[0017] 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 plumbum bromide.

[0018] [3] The radiation detector according to [1] or [2], wherein:

[0019] the semiconductor crystal portion is composed of a plurality of semiconductor crystals.

[0020] [4] The radiation detector according to any one of [1] to [3], wherein:

[0021] the insulating layer is disposed in a manner covering an entirety of the side surface of the semiconductor crystal portion.

[0022] [5] The radiation detector according to any one of [1] to [4], wherein:

[0023] the insulating layer projects toward the first electrode portion side with respect to a plane including a surface of the first electrode portion side of the semiconductor crystal portion.

[0024] [6] The radiation detector according to any one of [1] to [5], wherein:

[0025] the insulating layer contains at least one selected from the group consisting of silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluorine resin.

[0026] [7] The radiation detector according to any one of [1] to [6], wherein:

[0027] an insulating resistance of the insulating layer in a thickness direction is 1.5 kV / mm or more.

[0028] [8] The radiation detector according to any one of [1] to [7], wherein:

[0029] The insulation resistance of the insulating layer in the thickness direction is 19 kV / mm or more.

[0030] [9] The radiation detector according to any one of [1] to [8], wherein:

[0031] The thickness of the insulating layer is 150 μm or less.

[0032]

[10] The radiation detector according to any one of [1] to [9], wherein:

[0033] The thickness of the insulating layer is 50 μm or less.

[0034]

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

[10] , wherein:

[0035] The conductive layer contains at least one selected from the group consisting of copper, aluminum, gold, and alloys containing these elements.

[0036]

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

[11] , wherein:

[0037] The thickness of the conductive layer is 50 nm or more.

[0038]

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

[12] , wherein:

[0039] The thickness of the conductive layer is 150 nm or more.

[0040]

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

[13] , wherein:

[0041] The second portion includes the insulating layer and the conductive layer in this order from the side surface of the first electrode portion.

[0042]

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

[14] , wherein:

[0043] a circuit portion electrically connected to each of the plurality of pixel electrodes,

[0044] The circuit portion outputs information collected by each of the plurality of pixel electrodes as data after processing the information.

[0045]

[16] A radiation detection device comprising:

[0046] The radiation detector according to any one of [1] to

[15] ;

[0047] a power supply that applies a voltage to the radiation detector; and

[0048] A control section electrically connected to the radiation detector and the power supply.

[0049]

[17] The radiation detection apparatus according to

[16] , wherein:

[0050] The potential of the conductive layer is in a floating state.

[0051] Effects of the Invention

[0052] According to the present application, in a multi-channel type radiation detector, a radiation detector capable of improving the energy resolution of a plurality of pixel electrodes located at the outer peripheral portion of the radiation detector can be provided. Further, according to the present application, a radiation detection apparatus including the radiation detector can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is a cross-sectional view schematically showing one embodiment of a radiation detector.

[0054] Figure 2 is a plan view of a plurality of pixel electrodes.

[0055] Figure 3 is a plan view of a semiconductor crystal portion.

[0056] Figure 4 is a graph showing the results of the energy spectrum at the corner 1 point of the pixel electrode of Example 1 and Comparative Example 1.

[0057] Figure 5 is a graph showing the tendency of the average value of the FWHM of Examples 1 to 4 and Comparative Example 1.

[0058] Figure 6 is a graph showing the relationship between the thickness of the conductive layer and the average value of the FWHM. DETAILED DESCRIPTION

[0059] Hereinafter, embodiments of the present application will be described in detail. However, the present application is not limited to the following embodiments.

[0060] In the present specification, the "plurality of pixel electrodes located at the outer peripheral portion" refers to pixel electrodes arranged along the outer periphery of an electrode portion when the electrode portion in which a plurality of pixel electrodes exist is viewed from above. Further, in the present specification, the "plurality of pixel electrodes located at the central portion" refers to pixel electrodes arranged in a region from the center of an electrode portion to a length of half of the outer periphery when the electrode portion in which a plurality of pixel electrodes exist is viewed from above.

[0061] Figure 1is a cross-sectional view schematically showing one embodiment of a radiation detector. A radiation detector 100 (hereinafter also simply referred to as "detector 100") is a flat plate-shaped 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 substrate 16, a protective layer 17, an insulating layer 21, and a conductive layer 22. The semiconductor crystal portion 13 has two faces parallel to each other, and the first electrode portion 11 is formed on one of the two faces, and the second electrode portion 12 is formed on the other face.

[0062] The detector 100 includes a first portion 10 having, in the X direction, the protective layer 17, the first electrode portion 11, the semiconductor crystal portion 13, the second electrode portion 12, the connecting portion 15, and the circuit substrate 16 in this order. The first electrode portion 11 and the second electrode portion 12 oppose each other with the semiconductor crystal portion 13 interposed therebetween in the X direction. The radiation detector can not include at least one selected from the protective layer, the connecting portion, and the circuit substrate. That is, the first portion of the radiation detector has at least the first electrode portion, the semiconductor crystal portion, and the second electrode portion in this order.

[0063] The detector 100 includes a second portion 20 provided so as to surround a side surface 13SY (a face parallel to the X direction) of the semiconductor crystal portion 13. The second portion 20 has, in a direction perpendicular to the X direction (the Y direction and the Z direction), the insulating layer 21 and the conductive layer 22 in this order from the side surface 13SY of the semiconductor crystal portion 13. The side surface of the first electrode portion 11 of the detector 100 is entirely covered with the insulating layer 21, and the second portion 20 of the detector 100 includes 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 can not be covered with the insulating layer, and the second portion can not have the insulating layer and the conductive layer in this order from the side surface of the first electrode portion.

[0064] 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, in a case where the first electrode portion 11 is a cathode electrode, the second electrode portion 12 is an anode electrode.

[0065] The electrodes in the first electrode portion 11 and the second electrode portion 12 may include: a metal layer comprising at least one metal selected from copper, gold, platinum, silver, thallium, nickel, indium, and alloys thereof; and an underlayer comprising at least one metal selected from chromium, nickel, bismuth, and alloys thereof. The thickness of the underlayer may be, for example, 10 nm to 900 nm. The electrodes in the first electrode portion 11 and the second electrode portion 12 may include a low-resistance metal layer composed of a metal with a lower resistivity than the metal layer, provided on the semiconductor crystal portion 13 side. The low-resistance metal layer may be, for example, a gold layer. The thickness of the low-resistance metal layer may be, for example, 10 nm to 900 nm. An intermediate layer comprising a metal such as chromium, nickel, or bismuth may be provided between the low-resistance metal layer and the metal layer to improve adhesion between the two. The thickness of the intermediate layer may be, for example, 1 nm to 900 nm. The underlayer, low-resistance metal layer, and 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 stacked structure.

[0066] Metal layer / low resistance metal layer

[0067] Metal layer / intermediate layer / low resistance metal layer

[0068] Base layer / metal layer

[0069] Base layer / metal layer / low resistance metal layer

[0070] Base layer / metal layer / intermediate layer / low resistance metal layer

[0071] The first electrode portion 11 includes a single electrode (a common electrode). The electrodes in the first electrode portion 11 are electrically connected to a power supply. When the first electrode portion 11 functions as a cathode electrode, carriers (holes) generated by the interaction between incident radiation and the semiconductor crystal portion 13 are collected in the first electrode portion 11. Furthermore, when the first electrode portion 11 functions as a cathode electrode, a voltage of -50 V to -1000 V may be applied to the electrodes in the first electrode portion.

[0072] The first electrode portion 11 has a rectangular shape (square, oblong) when viewed from above in the X direction. The lengths of the first electrode portion 11 in the Y and Z directions can be, for example, 10 mm to 50 mm, respectively. The thickness of the first electrode portion 11 (the length in the X direction) can be, for example, 10 nm to 10,000 nm.

[0073] The second electrode portion 12, such as Figure 2 As shown, the second electrode unit 12 includes a plurality of pixel electrodes 12E and an insulating portion 14. The plurality of pixel electrodes 12E are arranged in the Y direction and the Z direction. The second electrode unit 12 includes a plurality of pixel electrodes 12E, thereby improving energy resolution.

[0074] The plurality of pixel electrodes 12E, in the case where the second electrode portion 12 is an anode electrode, that is, in the case where the pixel electrode 12E is an anode electrode, collect carriers (electrons) generated due to interaction between the incident radiation and the semiconductor crystal portion 13.

[0075] The first electrode portion 11 opposes the second electrode portion 12. All of the plurality of pixel electrodes 12E oppose the first electrode portion 11 with the semiconductor crystal portion 13 interposed therebetween. Alternatively, at least one electrode of the plurality of pixel electrodes can oppose the first electrode portion.

[0076] The second electrode portion 12 is rectangular (square, oblong) in plan view as viewed from the X direction.

[0077] Each of the plurality of pixel electrodes 12E is rectangular (square, oblong) in plan view as viewed from the X direction.

[0078] The insulating portion 14 is provided in order to prevent electrical interference between adjacent ones of the plurality of pixel electrodes 12E. As a resin material forming the insulating portion 14, a silicone resin, an acrylic resin, a urethane resin, a polyimide resin, a polyolefin resin, a fluorine resin, or the like can be cited; and an inorganic material having insulating properties such as silicon oxide, silicon nitride, and aluminum oxide. The insulating portion 14 can contain at least one selected from the group consisting of a silicone resin, an acrylic resin, a urethane resin, a polyimide resin, a polyolefin resin, and a fluorine resin from the viewpoint of sufficiently preventing electrical interference between adjacent ones of the plurality of pixel electrodes 12E. Alternatively, the insulating portion 14 can not be formed by a provided member but can be formed by a gap (air).

[0079] The semiconductor crystal portion 13 is composed of a semiconductor crystal that generates electrons and holes (carriers) by interaction with incident radiation (X-rays, γ-rays, or the like). That is, the semiconductor crystal portion 13 is composed of a crystal of a substance (compound semiconductor) that generates carriers by interaction with incident radiation. The semiconductor crystal portion 13 can have a semiconductor crystal containing at least one selected from the group consisting of thallium bromide, cadmium telluride, cadmium zinc telluride, and cesium plumbum tribromide from the viewpoint of superior absorption efficiency of radiation, and in particular, can have a semiconductor crystal containing thallium bromide.

[0080] The content of thallium bromide in the semiconductor crystal of the semiconductor crystal portion 13 can be 80% by mass or greater, 90% by mass or greater, 95% by mass or greater, or 98% by mass or greater, or can be substantially 100% by mass (in a manner in which the semiconductor crystal is composed of thallium bromide) based on the total mass of the semiconductor crystal from the viewpoint of superior absorption efficiency of radiation.

[0081] The thickness (length in the X direction) of the semiconductor crystal portion 13 can be, for example, 0.5 mm to 10 mm.

[0082] The semiconductor crystal portion 13 can be composed of one semiconductor crystal, or can be composed of a plurality of semiconductor crystals from the viewpoint of increasing the detection area. That is, the radiation detector can include, for one second electrode portion, a semiconductor crystal portion having one semiconductor crystal, or can include, for one second electrode portion, a semiconductor crystal portion having a plurality of semiconductor crystals. The number of semiconductor crystals in the case where the semiconductor crystal portion is composed of a plurality of semiconductor crystals is not particularly limited, and the semiconductor crystal portion can be composed of, for example, four semiconductor crystals, or can be composed of, for example, nine semiconductor crystals.

[0083] Figure 3 A plan view of the case where the semiconductor crystal portion 13 is composed of a plurality of semiconductor crystals is shown. In Figure 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 the semiconductor crystals 13A are joined to each other.

[0084] The four semiconductor crystals 13A each have substantially the same composition, and as a material constituting the semiconductor crystal 13A, thallium bromide, cadmium telluride, cadmium zinc telluride, cesium lead tribromide, or the like can be cited. The thickness (length in the X direction) of the four semiconductor crystals 13A is substantially the same for each of the semiconductor crystals, and can be within the range of the thickness of the semiconductor crystal portion 13 described above.

[0085] The resin layer 18 is formed of, for example, silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, fluorine resin, or the like. The resin layer 18 can be formed of, for example, humiseal manufactured by AR BROWN Co., Ltd. The thickness (length in the X direction) of the resin layer 18 can be substantially the same as the thickness of the semiconductor crystal 13A. The width (length between the semiconductor crystals 13A. Length in the Y direction or the Z direction) of the resin layer 18 can be, for example, 0.01 mm to 1 mm.

[0086] The connection portion 15 electrically connects each of the plurality of pixel electrodes 12E of the second electrode portion 12 to the circuit substrate 16 described later. The connection portion 15 is, for example, a conductive material such as solder, conductive adhesive, or the like.

[0087] The circuit substrate (circuit portion) 16 has a wiring pattern and a signal processing circuit connected to the connection portion 15. As a material of the circuit substrate 16, silicon, ceramic, quartz, glass, and plastic can be listed. As the circuit substrate 16, for example, a glass hybrid substrate (CEM-3) obtained by impregnating an epoxy resin into a base material obtained by mixing a glass cloth and a glass nonwoven cloth, a glass epoxy substrate (FR-4) obtained by impregnating an epoxy resin into a material in which a cloth made of glass fiber is overlapped, a metal heat dissipation substrate in which copper, aluminum, or the like is used as a base material, or the like can be used. The signal processing circuit is, for example, an ASIC (Application Specific Integrated Circuit). The signal processing circuit processes information (current value information) of carriers collected by each of the plurality of pixel electrodes 12E and outputs the information to the control portion as radiation image data (data). The signal processing circuit outputs the radiation image data to the control portion continuously or intermittently. The radiation image data can be the radiation image itself or data used to generate the radiation image. The signal processing circuit can be provided on a substrate other than the circuit substrate 16.

[0088] The protective layer 17 protects the first electrode portion 11. The protective layer is not only for protecting the first electrode portion but also can be provided for protecting the second electrode portion, the conductive layer, the insulating layer, the substrate, or the like.

[0089] The protective layer 17 can be formed of a material having insulating properties, for example. As a material having insulating properties, for example, resin materials such as silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, fluorine resin, or the like; inorganic materials having insulating properties such as silicon oxide, silicon nitride, aluminum oxide, or the like can be listed.

[0090] The thickness (length in the X direction) of the protective layer 17 can be, for example, 0.1 mm to 2.0 mm. By the thickness of the protective layer 17 being 0.5 mm or more, the first electrode portion 11 can be sufficiently protected.

[0091] The insulating layer 21 is provided so as 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 can cover at least a part of the side surface 13SY of the semiconductor crystal portion 13, and can be formed so as to cover the entire side surface 13SY of the semiconductor crystal portion 13 from the viewpoint of further improving the energy resolution of the plurality of pixel electrodes 12E located in the outer peripheral portion and the viewpoint of easily making the detection characteristics of each electrode of the plurality of pixel electrodes 12E uniform. As the insulating layer 21, for example, a glass epoxy substrate (FR-4) obtained by impregnating an epoxy resin into a material in which a cloth made of glass fiber is overlapped, a glass hybrid substrate (CEM-3) obtained by impregnating an epoxy resin into a base material obtained by mixing a glass cloth and a glass nonwoven cloth, a metal heat dissipation substrate in which copper, aluminum, or the like is used as a base material, or the like can be used. Figure 3In the case where the semiconductor crystal portion is composed of a plurality of semiconductor crystals 13A, as illustrated, the insulating layer 21 is not provided so as to surround the side surface of each semiconductor crystal 13A, but is provided so as to surround the side surface of the semiconductor crystal portion composed of the plurality of semiconductor crystals 13A. The insulating layer 21 can be formed not only on the side surface 13SY of the semiconductor crystal portion 13, but also on the side surface of the first electrode portion 11 and / or the second electrode portion 12.

[0092] The insulating layer 21 protrudes toward the first electrode portion 11 side with respect to the plane of the surface 13SX of the first electrode portion 11 side including the semiconductor crystal portion 13. By the insulating layer 21 protruding toward the first electrode portion 11 side with respect to the plane of the surface 13SX of the first electrode portion 11 side including the semiconductor crystal portion 13, it is possible to reliably suppress short-circuiting (discharge) between the electrode of the first electrode portion 11 and the conductive layer 22. Further, in the case where the protective layer 17 is provided on the first electrode portion 11, by the insulating layer 21 protruding toward the first electrode portion 11 side with respect to the plane of the surface 13SX of the first electrode portion 11 side including the semiconductor crystal portion 13, in the case where the material forming the protective layer 17 is a liquid, the protruding portion of the insulating layer 21 can suppress the material forming the protective layer 17 from flowing out to the side surface 13SY of the semiconductor crystal portion 13, and in the case where a plurality of radiation detectors are arranged adjacent to each other, it is easy to arrange the radiation detectors close to each other. The insulating layer 21 can protrude 1 mm or more with respect to the plane of the surface 13SX of the first electrode portion 11 side including the semiconductor crystal portion 13, or can protrude more than 0 mm and less than 1 mm. The insulating layer can not protrude toward the first electrode portion side with respect to the plane of the surface of the first electrode portion side including the semiconductor crystal portion.

[0093] The insulating layer 21 is formed of a material having insulating properties. As the material forming the insulating layer 21, from the viewpoint of ensuring sufficient insulating properties, for example, a resin material such as silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, fluorine resin, or the like; an inorganic material having insulating properties such as silicon oxide, silicon nitride, aluminum oxide, or the like can be exemplified. The insulating layer 21 can also be formed of a void (air). The insulating layer 21, from the viewpoint of ensuring sufficient insulating properties, can contain at least one selected from the group consisting of silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluorine resin.

[0094] The insulating resistance of the insulating layer 21 in the thickness direction, from the viewpoint of ensuring sufficient insulating properties, can 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 insulating resistance of the insulating layer 21 in the thickness direction is not particularly limited, and can be, for example, 1000 kV / mm or less, or 500 kV / mm or less.

[0095] The voltage resistance of the insulating layer 21 in the thickness direction (a direction perpendicular to the X direction) can 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 from the viewpoint of ensuring sufficient insulation. The voltage resistance of the insulating layer 21 can be 20 kV or less, 15 kV or less, 10 kV or less, 8 kV or less, or 7 kV or less. The voltage resistance of the insulating layer 21 can be calculated by the product of the insulation resistance in the thickness direction of the insulating layer 21 and the thickness of the insulating layer 21.

[0096] The thickness of the insulating layer 21 (a length in a direction perpendicular to the X direction) can 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 outer peripheral portion and the viewpoint of easily making the detection characteristics of each of the plurality of pixel electrodes 12E uniform. The thickness of the insulating layer 21 can 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 can be 10 μm to 300 μm, 20 μm to 200 μm, or 30 μm to 150 μm.

[0097] The conductive layer 22 is formed on the entire surface of the insulating layer 21. By the detector 100 having the conductive layer 22, it is considered that the electric field intensity of the outer peripheral portion of the detector 100 becomes uniform, and the energy resolution of the plurality of pixel electrodes 12E located in the outer peripheral portion can be improved. The conductive layer can also be formed on a part of the surface of the insulating layer.

[0098] The conductive layer 22 is formed of a material having sufficient conductivity. As the material forming the conductive layer 22, from the viewpoint of ensuring sufficient conductivity, for example, a metal material such as copper, gold, platinum, silver, nickel, indium, and an alloy containing these elements; a carbon-containing material such as carbon and a conductive polymer can be cited. From the viewpoint of being able to improve the energy resolution of the plurality of pixel electrodes 12E located in the outer peripheral portion, the conductive layer 22 can contain at least one selected from copper, aluminum, gold, and an alloy containing these elements.

[0099] The potential of the conductive layer 22 can be formed 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 outer peripheral portion can be further improved, and the detection characteristics of each of the plurality of pixel electrodes 12E can be easily made uniform. The conductive layer 22 can also be given a potential in a non-floating state, and can be a ground potential.

[0100] The conductive layer 22 can be formed directly on the surface of the insulating layer 21 by evaporation or the like, or can be formed on the surface of the insulating layer 21 with an adhesive layer or the like interposed therebetween. In the case where the conductive layer 22 is formed on the surface of the insulating layer 21 with an adhesive layer interposed therebetween, the conductive layer 22 can be formed on the surface of the insulating layer 21 using, for example, a conductive tape.

[0101] The conductive layer 22 protrudes toward the first electrode portion 11 side with respect to the plane of the surface 13SX of the first electrode portion 11 side including the semiconductor crystal portion 13. The conductive layer 22 can protrude by 1 mm or more with respect to the plane of the surface 13SX of the first electrode portion 11 side including the semiconductor crystal portion 13, or can protrude by more than 0 mm and 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 can not protrude toward the first electrode portion side with respect to the plane of the surface of the first electrode portion side including the semiconductor crystal portion. From the viewpoint of reliably making the electric field distribution within the semiconductor crystal portion uniform, the conductive layer is preferably formed at least to a position on the same plane with respect to the plane of the surface 13SX of the first electrode portion side including the semiconductor crystal portion. Further, 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 not on the same plane with respect to the plane of the surface 13SX of the first electrode portion side including the semiconductor crystal portion (i.e., the conductive layer is formed in a state of protruding with respect to the first electrode or in a state of not protruding with respect to the first electrode).

[0102] The thickness (length in a direction perpendicular to the X direction) of the conductive layer 22 can 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 viewpoints of further improving the energy resolution of the plurality of pixel electrodes 12E located in the outer peripheral portion and easily making the detection characteristics of the respective electrodes of the plurality of pixel electrodes 12E uniform. The thickness of the conductive layer 22 can be 200 nm or more, 300 nm or more, or 400 nm or more from the viewpoint of further improving the energy resolution of the plurality of pixel electrodes 12E located in the outer peripheral portion. The thickness of the conductive layer 22 can be 1000 nm or less, 800 nm or less, 600 nm or less, or 500 nm or less from the viewpoint of ensuring sufficient conductivity. From these viewpoints, the thickness of the conductive layer 22 can be 10 nm to 1000 nm, 30 nm to 800 nm, or 50 nm to 600 nm.

[0103] By increasing the thickness of the conductive layer 22, the energy resolution of the pixel electrodes 12E located at the outer peripheral portion is superior to that of the pixel electrodes located at the central portion. This is considered to be because, in the case where the electric field intensity of the pixel electrodes 12E located at the outer peripheral portion and the pixel electrodes 12E located at the central portion is the same, the pixel electrodes 12E located at the outer peripheral portion have fewer adjacent pixel electrodes, and accordingly, are less likely to be affected by noise from the surrounding pixel electrodes.

[0104] The above-described radiation detector can be used for a radiation detection device, and more specifically, can be used for a SPECT (Single Photon Emission Computed Tomography) device, a PET (Positron Emission Tomography) device, a gamma camera, a Compton camera, an imaging spectrometer, and the like.

[0105] According to the above-described radiation detector, the energy resolution of the pixel electrodes 12E located at the outer peripheral portion can be improved. As for the reason, the inventors of the present application speculate that this is due to the distribution of the electric field formed inside the semiconductor crystal portion 13 by the potential difference applied between the first electrode portion 11 and the second electrode portion 12 being disturbed along the outer edge portion of the semiconductor crystal portion 13. That is, it is speculated that, in the central portion, an equipotential surface parallel to one face (YZ plane) of the semiconductor crystal portion 13 is formed, becoming a uniform electric field distribution, whereas in the vicinity of the outer edge portion of the semiconductor crystal portion 13, the equipotential surface is distorted outward, and the electric field distribution becomes non-uniform. As a result of the electric field distribution becoming non-uniform at the outer edge portion of the semiconductor crystal portion 13, even if carriers are generated inside the semiconductor crystal portion 13 due to the incident radiation, the collection efficiency of the carriers of the pixel electrodes 12E located at the outer peripheral portion decreases, and thus the energy resolution decreases compared to the central portion. On the other hand, by sequentially providing the insulating layer 21 and the conductive layer 22 on the side surface of the radiation detection element, the distortion of the electric field in the vicinity of the outer edge portion of the semiconductor crystal portion 13 can be suppressed. It can thus be speculated that, because the electric field formed inside the semiconductor crystal portion 13 becomes uniform, the decrease in the collection efficiency of the carriers of the pixel electrodes 12E located at the outer peripheral portion can be suppressed, and the energy resolution of the pixel electrodes 12E located at the outer peripheral portion can be improved.

[0106] Further, according to the above-described radiation detector, the energy resolution of the entire multi-channel detector is improved by increasing the energy resolution of the plurality of pixel electrodes 12E located at the outer peripheral portion. Further, according to the above-described radiation detector, since the energy resolution of each pixel electrode becomes uniform, high-precision imaging can be achieved in the case of applying to a plurality of simultaneous imaging that simultaneously measures radiation of different energies.

[0107] In the case of applying the radiation detector to a radiation detection device, the radiation detection device includes, in addition to the radiation detector, a power supply that applies a voltage to the radiation detector, and a control portion that is electrically connected to the radiation detector and the power supply. That is, another embodiment of the present application is a radiation detection device including the above-described radiation detector, a power supply that applies a voltage to the radiation detector, and a control portion that is electrically connected to the radiation detector and the power supply.

[0108] In the radiation detection device, the power supply applies a voltage to the radiation detector in accordance with a control signal from the control portion. The power supply applies, for example, a high voltage (HV) to the radiation detector. The voltage (ON voltage value) applied to the radiation detector by the power supply can be arbitrarily set, for example, to -50 to -1000 V.

[0109] The control portion is electrically connected to the radiation detector and the power supply. The control portion is constituted by, for example, an FPGA (Field-Programmable Gate Array). The control portion acquires the radiation image data output from the radiation detector, and outputs the radiation image data to a control device via an input-output interface. The control portion can also generate a radiation image based on the acquired radiation image data.

[0110] Embodiment

[0111] Hereinafter, the present application will be described more specifically by citing examples. However, the present application is not limited to these examples.

[0112] (Example 1)

[0113] A laminate having, in order, a common electrode made of thallium alloy having a size of 20 mm x 20 mm x thickness 300 nm, a thallium bromide crystal (semiconductor crystal) having a thickness of 3 mm, a pixel electrode made of thallium alloy having a size of 20 mm x 20 mm x thickness 3 mm (pixel number 8 x 8), and a circuit substrate including an ASIC was produced.

[0114] A polyimide resin layer (kapton tape, manufactured by DU PONT-TORAY CO., LTD., insulation resistance: 380 kV / mm) having a thickness of 150 μm was formed as an insulating layer so as to cover the entire side surface of the thallium bromide crystal constituting the layered body. At this time, the insulating layer protruded 0.5 mm from the plane of the surface of the common electrode side including the thallium bromide crystal. Subsequently, a gold layer having a thickness of 0.3 μm was formed as a conductive layer by evaporation on the surface of the polyimide resin layer, and a radiation detector was obtained. At this time, the gold layer formed was in a floating state.

[0115] (Example 2)

[0116] 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.

[0117] (Example 3)

[0118] 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.

[0119] (Example 4)

[0120] 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.

[0121] (Comparative Example 1)

[0122] 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.

[0123] [Evaluation]

[0124] Figure 4 Results of the energy spectrum at the 1 point of the corner portion of the pixel electrode of Example 1 and Comparative Example 1 are shown. With respect to Examples 1 to 4 and Comparative Example 1, Table 1 and Figure 5 The average value of the FWHM (Full-width at Half-Maximum) of the 16 points of the central portion of the pixel electrode, the average value of the FWHM of the 28 points of the outer edge portion of the pixel electrode, and the average value of the FWHM of the 4 points of the corner portion of the pixel electrode are shown. In addition, the central portion of the pixel electrode is 16 pixel electrodes selected in order of proximity to the center of the pixel electrode (region A of Figure 2 ), the outer edge portion of the pixel electrode is 28 pixel electrodes selected in order of remoteness from the center of the pixel electrode (region B of Figure 2 ), and the corner portion of the pixel electrode is 4 pixel electrodes selected in order of remoteness from the center of the pixel electrode (region C of Figure 2(Region C). A smaller average FWHM value indicates better energy resolution. Furthermore, the closer the average FWHM values ​​of the 16 central points, the average FWHM values ​​of the 28 outer edge points, and the average FWHM values ​​of the four corner points are to the same degree (within ±1%), the more uniform the detection characteristics (energy resolution) of the multiple pixel electrodes are.

[0125] Table 1

[0126]

[0127] (Example 5)

[0128] A radiation detector was fabricated in the same manner as in Example 3, except that the insulating layer was formed so as to protrude 1.5 mm from the plane of the surface on the common electrode side including the thallium bromide crystal. The average FWHM value of the 16 points in the center of the pixel electrode was 7.8%, the average FWHM value of the 28 points in the outer edge was 7.4%, and the average FWHM value of the four corner points was 7.4%.

[0129] (Example 6)

[0130] A radiation detector was fabricated in the same manner as in Example 4, except that the insulating layer was formed so as to protrude 1.5 mm from the plane of the surface on the common electrode side including the thallium bromide crystal. The average FWHM value of the 16 points in the center of the pixel electrode was 7.8%, the average FWHM value of the 28 points in the outer edge was 7.0%, and the average FWHM value of the four corner points was 7.0%.

[0131] (Examples 7 to 11, Comparative Examples 2 and 3)

[0132] A radiation detector was fabricated in the same manner as in Example 1, except that the insulating layer and conductive layer were modified as shown in Table 2. The terms "insulating layer" and "conductive layer" in the table indicate that they are formed from the following materials. "-" in the "conductive layer" column in Table 2 means that no conductive layer was formed. Furthermore, in the "Evaluation" column in Table 2, the radiation detector's energy resolution at the periphery (28 points at the outer edge and 4 points at the corners) is marked "A" if it is comparable to that of Example 1, "B" if it is slightly inferior to that of Example 1 but superior to that of Comparative Example 1, and "C" if it is comparable to that of Comparative Example 1.

[0133] Polyimide resin layer (manufactured by DU PONT-TORAY CO., LTD., Kapton tape, thickness: 35 μm, insulation resistance: 380 kV / mm)

[0134] • Fluororesin layer (VALFLON (registered trademark) manufactured by VALQUA, LTD., thickness: 50 μm, insulation resistance: 19 kV / mm)

[0135] • Silicone resin layer (manufactured by FUJI SILYSIA CHEMICAL LTD., thickness: 250 μm, insulation resistance: 26 kV / mm)

[0136] • Acrylic resin layer (humiseal 1B66NS manufactured by AR BROWN Co., Ltd., thickness: 20 μm, insulation resistance: 22.4 kV / mm)

[0137] • Aluminum layer (formed by evaporation, thickness: 0.3 μm)

[0138] • Copper layer (manufactured by TERA MFG., product name 8323, copper tape, thickness: 70 μm)

[0139] Table 2

[0140] insulating layer conductive layer evaluation Example 7 polyimide resin layer aluminum layer A Example 8 polyimide resin layer gold layer A Example 9 polyimide resin layer copper layer B Example 10 fluororesin layer copper layer B Example 11 silicone resin layer copper layer B Comparative Example 2 polyimide resin layer _ C Comparative Example 3 acrylic resin layer _ C

[0141] (Examples 12 to 14)

[0142] A radiation detector was produced in the same manner as in Example 7 except that the thickness of the aluminum layer was changed as shown in Table 3. Table 3 and Figure 6 The average of the FWHM of the central portion 16 points of the pixel electrode, the average of the FWHM of the outer edge portion 28 points, and the average of the FWHM of the corner portion 4 points were shown.

[0143] Table 3

[0144]

[0145] Explanation of Reference Numerals

[0146] 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 surface, 14…insulating portion, 15…connecting portion, 16…circuit substrate, 17…protective layer, 18…resin layer, 20…second portion, 21…insulating layer, 22…conductive layer, 100…radiation detector.

Claims

1. A radiation detector, characterized in that: include: a first portion, which sequentially includes a first electrode portion, a semiconductor crystal portion, and a second electrode portion opposite to the first electrode portion; and a second portion provided so as to surround the side surfaces of the semiconductor crystal portion, The second portion has an insulating layer and a conductive layer in this order from the side surface of the semiconductor crystal portion. The second electrode portion includes a plurality of pixel electrodes.

2. The radiation detector according to claim 1, wherein: The semiconductor crystal portion includes a semiconductor crystal containing at least one selected from 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 composed of a plurality of semiconductor crystals.

4. The radiation detector according to claim 1, wherein: The insulating layer is arranged 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 relative to a plane including a surface of the semiconductor crystal portion on the first electrode portion side.

6. The radiation detector according to claim 1, wherein: The insulating layer includes at least one selected from silicone resin, acrylic resin, polyurethane resin, polyimide resin, polyolefin resin, and fluororesin.

7. The radiation detector according to claim 1, wherein: The insulation strength of the insulating layer in the thickness direction is greater than or equal to 1.5 kV / mm.

8. The radiation detector according to claim 1, wherein: The insulation strength of the insulating layer in the thickness direction is greater than or equal to 19 kV / mm.

9. The radiation detector according to claim 1, wherein: The thickness of the insulating layer is less than 150 μm.

10. The radiation detector according to claim 1, wherein: The thickness of the insulating layer is less than 50 μm.

11. The radiation detector according to claim 1, wherein: The conductive layer includes at least one selected from copper, aluminum, gold, and alloys containing these elements.

12. The radiation detector according to claim 1, wherein: The thickness of the conductive layer is greater than 50 nm.

13. The radiation detector according to claim 1, wherein: The thickness of the conductive layer is greater than 150 nm.

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. The radiation detector according to claim 1, wherein: further comprising a circuit portion electrically connected to each of the plurality of pixel electrodes, The circuit unit processes information collected for each of the plurality of pixel electrodes and outputs the processed information as data.

16. A radiation detection device, characterized in that: include: The radiation detector according to any one of claims 1 to 15; a power source for applying a voltage to the radiation detector; and A control unit is electrically connected to the radiation detector and the power supply.

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

18. The radiation detection device according to claim 16, wherein: The potential of the conductive layer is ground potential.

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