RADIATION DETECTOR, AND RADIATION DETECTOR ARRAY

The radiation detector includes a scintillator, first and second semiconductor photodetectors, a first wiring member electrically connected to the first semiconductor photodetector, and a second wiring member electrically connected to the second semiconductor photodetector. The scintillator includes a pair of end surfaces opposing each other in a first direction and first and second side surfaces opposing each other in a second direction intersecting the first direction, and has a rectangular shape when viewed in the first direction. The first and second side surfaces couple the pair of end surfaces. The first semiconductor photodetector includes a first semiconductor substrate disposed to oppose the first side surface. The second semiconductor photodetector includes a second semiconductor substrate disposed to oppose the second side surface.

TECHNICAL FIELD

The present invention relates to a radiation detector and a radiation detector array.

BACKGROUND ART

Known radiation detectors include a scintillator having a hexahedron shape and a semiconductor photodetector including a semiconductor substrate disposed on the scintillator (for example, refer to Patent Literature 1). The scintillator generates a scintillation light in response to entry of radiation. The semiconductor photodetector detects the generated scintillation light.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

An object of a first aspect of the present invention is to provide a radiation detector having high time resolution and high detection sensitivity. Objects of second and third aspects of the present invention are to provide a radiation detector array including radiation detectors having high time resolution and high detection sensitivity.

Solution to Problem

The present inventors have intensively studied radiation detectors having high time resolution and high detection sensitivity. As a result, the present inventors have newly obtained the following knowledge and conceived the present invention. Patent Literature 1 does not disclose a radiation detector having high time resolution and high detection sensitivity.

When radiation enters a scintillator that includes a pair of end surfaces opposing each other in a first direction and is longer in the first direction, from one of the pair of end surfaces, the scintillator reliably absorbs the radiation in a high energy range and generates scintillation lights. In a configuration in which a semiconductor photodetector is disposed on another end surface of the pair of end surfaces, the scintillator can easily and reliably absorb the radiation in the high energy range.

The semiconductor photodetector detects the scintillation light emitted from the other end surface. In a configuration in which a length of the scintillator in the first direction is larger than a length of the scintillator in a direction intersecting the first direction, it is difficult to obtain high time resolution. Side surfaces coupling the pair of end surfaces and extending in the first direction are disposed at a shorter distance from the scintillation light generation point than the other end surface is. Therefore, semiconductor photodetectors disposed on the side surfaces extending in the first direction easily detect the scintillation lights with high time resolution. In a radiation detector, it is desirable to arrange the semiconductor photodetectors at positions where individual scintillation lights simultaneously generated at the same position can be detected at a short distance. This arrangement of the semiconductor photodetectors enables incident radiation to be detected with high time resolution.

In a configuration in which the scintillator includes a plurality of side surfaces, the semiconductor photodetectors can be disposed on the plurality of side surfaces, respectively. A radiation detector in which the semiconductor photodetectors are disposed on the plurality of side surfaces, respectively, achieves high detection sensitivity, as compared with a radiation detector in which one semiconductor photodetector is disposed only on one end surface.

A radiation detector according to a first aspect includes: a scintillator including a pair of end surfaces opposing each other in a first direction, and a first side surface and a second side surface opposing each other in a second direction intersecting the first direction and coupling the pair of end surfaces, the scintillator having a rectangular shape when viewed in the first direction; a first semiconductor photodetector including a first semiconductor substrate disposed to oppose the first side surface; a second semiconductor photodetector including a second semiconductor substrate disposed to oppose the second side surface; a first wiring member electrically connected to the first semiconductor photodetector; and a second wiring member electrically connected to the second semiconductor photodetector. A length of the scintillator in the first direction is longer than a length of the scintillator in the second direction and a length of the scintillator in a third direction parallel to the first side surface. A length of the first side surface in the first direction is longer than a width of the first side surface in the third direction. A length of the second side surface in the first direction is longer than a width of the second side surface in the third direction. The first semiconductor substrate includes a first portion covered with the first side surface, and a second portion disposed with the first portion in the first direction and exposed from the first side surface. The second semiconductor substrate includes a third portion covered with the second side surface, and a fourth portion disposed with the third portion in the first direction and exposed from the second side surface. Each of the first semiconductor photodetector and the second semiconductor photodetector includes a plurality of photodetection regions including at least one avalanche photodiode arranged to operate in Geiger mode, and at least one quenching resistor electrically connected in series with one of an anode or a cathode of a corresponding avalanche photodiode of the at least one avalanche photodiode. The first semiconductor photodetector includes a plurality of first electrodes electrically connected to the at least one quenching resistor included in the first semiconductor photodetector and included in a corresponding photodetection region of the plurality of photodetection regions, and a second electrode electrically connected to another of the anode or the cathode of the avalanche photodiode included in the first semiconductor photodetector and included in the corresponding photodetection region of the plurality of photodetection regions. The second semiconductor photodetector includes a plurality of third electrodes electrically connected to the at least one quenching resistor included in the second semiconductor photodetector and included in the corresponding photodetection region of the plurality of photodetection regions, and a fourth electrode electrically connected to another of the anode or the cathode of the avalanche photodiode included in the second semiconductor photodetector and included in the corresponding photodetection region of the plurality of photodetection regions. The plurality of photodetection regions included in the first semiconductor photodetector are disposed in the first portion. The plurality of first electrodes and the second electrode are disposed in the second portion. The plurality of photodetection regions included in the second semiconductor photodetector are disposed in the third portion. The plurality of third electrodes and the fourth electrode are disposed in the fourth portion. The first wiring member includes a plurality of conductors electrically connected to a corresponding first electrode of the plurality of first electrodes, and a conductor connected to the second electrode. The second wiring member includes a plurality of conductors electrically connected to a corresponding third electrode of the plurality of third electrodes, and a conductor connected to the fourth electrode.

According to the first aspect, the radiation detector includes the scintillator that is elongated in the first direction, the first semiconductor substrate disposed on the first side surface of the scintillator, and the second semiconductor substrate disposed on the second side surface of the scintillator. The first semiconductor photodetector detects the scintillation light incident on the first side surface. The second semiconductor photodetector detects the scintillation light incident on the second side surface. A length of the scintillator in the second direction is shorter than a length of the scintillator in the first direction. Therefore, a distance from the scintillation light generation point to each of the first side surface and the second side surface is short. An arrival time of a scintillation light to each of the first and second semiconductor photodetectors is short, and the first aspect achieves high time resolution. The first aspect includes the first semiconductor photodetector and the second semiconductor photodetector. Therefore, the first aspect achieves high detection sensitivity as compared with a radiation detector including a single semiconductor photodetector disposed on one side surface of a scintillator.

The first aspect includes the first semiconductor photodetector and the second semiconductor photodetector, each of which includes the plurality of photodetection regions disposed in the first direction. For example, a distance between the scintillation light generation point and one end surface of the scintillator in the first direction is obtained from a position on the photodetection region where the most scintillation lights are detected, of the plurality of photodetection regions. Therefore, a magnitude of energy of radiation incident on the one end surface the scintillator is accurately measured. As a result, the first aspect achieves detection sensitivity.

In the first aspect, when viewed in the second direction, one region formed by an outline of the plurality of photodetection regions included in the first semiconductor substrate may have an outline shape corresponding to an outline shape of the first side surface. When viewed in the second direction, one region formed by the outline of the plurality of photodetection regions included in the second semiconductor substrate may have an outline shape corresponding to an outline shape of the second side surface.

In a configuration in which the one region formed by the outline of the plurality of photodetection regions included in the first semiconductor substrate has the outline shape corresponding to the outline shape of the first side surface, the plurality of photodetection regions tend not to be disposed at positions on the first semiconductor substrate where no scintillation lights can be received. Therefore, increase in dark count and capacitance in the photodetection regions included in the first semiconductor substrate is curbed. In a configuration in which the one region formed by the outline of the plurality of photodetection regions included in the second semiconductor substrate has the shape corresponding to the outline shape of the second side surface, the plurality of photodetection regions tend not to be disposed at positions on the second semiconductor substrate where no scintillation lights can be received. Therefore, increase in dark count and capacitance in the photodetection regions included in the second semiconductor substrate is curbed. These configurations reduce detection errors of scintillation lights. As a result, this configuration reliably improves the time resolution and the detection sensitivity of the first semiconductor photodetector and the second semiconductor photodetector.

In the first aspect, the scintillator may include a plurality of portions disposed independently of each other in the first direction. Each of the plurality of portions may be positioned corresponding to the corresponding photodetection region of the plurality of photodetection regions disposed in each of the first semiconductor substrate and the second semiconductor substrate. Each of the plurality of portions may include a pair of opposing surfaces that oppose each other in the first direction, and a first coupling surface and a second coupling surface that couples the pair of opposing surfaces. The first coupling surface may oppose the first semiconductor substrate. The second coupling surface may oppose the second semiconductor substrate and oppose the first coupling surface in the second direction.

In a configuration in which the scintillator includes the plurality of portions disposed independently of each other in the first direction, the scintillation light generated in each portion is confined in the corresponding portion. The photodetection region corresponding to the portion reliably detects the scintillation light generated in the portion. Therefore, this configuration reliably achieves high detection sensitivity.

In the first aspect, the plurality of portions may be joined to each other.

A configuration in which the plurality of portions are joined to each other improves physical strength of the scintillator. Therefore, this configuration more reliably achieves high detection sensitivity.

The first aspect may include a light reflecting member. The light reflecting member may be disposed between the plurality of portions.

In a configuration in which the light reflecting member is disposed between the plurality of portions, the scintillation light generated in each portion is reliably confined in the corresponding portion. The photodetection region corresponding to the corresponding portion more reliably detects the scintillation light generated in the corresponding portion. Therefore, this configuration still more reliably achieves high detection sensitivity.

In the first aspect, when viewed in the second direction, each of the plurality of photodetection regions included in the first semiconductor substrate may have an outline shape corresponding to an outline shape of the first coupling surface of a corresponding portion of the plurality of portions, the first coupling surface that opposes the first semiconductor substrate. When viewed in the second direction, each of the plurality of photodetection regions included in the second semiconductor substrate may have the outline shape corresponding to the outline shape of the second coupling surface of a corresponding portion of the plurality of portions, the second coupling surface that opposes the second semiconductor substrate.

In a configuration in which each of the plurality of photodetection regions included in the first semiconductor substrate has the outline shape corresponding to the outline shape of the first coupling surface of the corresponding portion of the plurality of portions, the first coupling surface that opposes the first semiconductor substrate, the plurality of photodetection regions tend not to be disposed at positions on the first semiconductor substrate where no scintillation lights can be received. In a configuration in which each of the plurality of photodetection regions included in the second semiconductor substrate has the outline shape corresponding to the outline shape of the second coupling surface of the corresponding portion of the plurality of portions, the second coupling surface that opposes the second semiconductor substrate, the plurality of photodetection regions tend not to be disposed at positions on the second semiconductor substrate where no scintillation lights can be received. Therefore, this configuration curbs increase in dark count and capacitance in the plurality of photodetection regions. As a result, this configuration reliably improves the time resolution and the detection sensitivity of the radiation detector.

In the first aspect, the plurality of photodetection regions may include a first photodetection region and a second photodetection region closer to the second portion than the first photodetection region. A width of a conductive wire electrically connecting the first electrode corresponding to the first photodetection region and the first photodetection region may be larger than a width of a conductive wire electrically connecting the first electrode corresponding to the second photodetection region and the second photodetection region.

In a configuration in which the width of the conductive wire electrically connecting the first electrode corresponding to the first photodetection region and the first photodetection region is larger than the width of the conductive wire electrically connecting the first electrode corresponding to the second photodetection region and the second photodetection region, an electrical resistance difference is reduced. A length of the conductive wire electrically connecting the first electrode corresponding to the first photodetection region and the first photodetection region is longer than a length of the conductive wire electrically connecting the first electrode corresponding to the second photodetection region and the second photodetection region. As the length of the conductive wire increases, the electrical resistance of the conductive wire increases. As the width of the conductive wire increases, the electrical resistance of the conductive wire decreases. Therefore, in a configuration in which a width of a long conductive wire is larger than a width of a short conductive wire, the electrical resistance difference between the electrical resistance of the long conductive wire and the electrical resistance of the short conductive wire is reduced. Therefore, this configuration reliably improves the time resolution and the detection sensitivity of the radiation detector.

The first aspect may include a reinforcement body disposed between the second portion and the fourth portion. The reinforcement body may cover the second portion and the fourth portion and couple the second portion and the fourth portion.

In a configuration in which the reinforcement body disposed between the second portion and the fourth portion is provided, the reinforcement body disposed between the second portion and the fourth portion improves mechanical strength of both the second portion and the fourth portion.

In the first aspect, the first semiconductor substrate may include a first surface opposing the scintillator in the second direction and a second surface opposing the first surface in the second direction. The second semiconductor substrate may include a third surface opposing the scintillator in the second direction and a fourth surface opposing the third surface in the second direction. The second surface and the fourth surface may include polished surfaces.

In a configuration in which the second surface includes the polished surface, the first semiconductor substrate can be thinned by polishing the second surface. In a configuration in which the fourth surface includes a polished surface, the second semiconductor substrate can be thinned by polishing the fourth surface. A size of the radiation detector can be reduced in a thickness direction of the first semiconductor substrate. A size of the radiation detector can be reduced in a thickness direction of the second semiconductor substrate.

The first aspect may include: a first base including a fifth surface and a sixth surface opposing each other in the second direction and be disposed such that the first semiconductor substrate is positioned between the fifth surface and the scintillator; a second base including a seventh surface and an eighth surface opposing each other in the second direction and be disposed such that the second semiconductor substrate is positioned between the seventh surface and the scintillator; a plurality of first terminals disposed on the fifth surface; a second terminal disposed on the fifth surface; a plurality of third terminals disposed on the seventh surface; a fourth terminal disposed on the seventh surface; a first wire electrically connecting each of the plurality of first terminals and each of the first electrodes; a second wire electrically connecting the second terminal and the second electrode; a third wire electrically connecting each of the plurality of third terminals and each of the third electrodes; and a fourth wire electrically connecting the fourth terminal and the fourth electrode. The first base may include a fifth portion covered with the first semiconductor substrate and a sixth portion disposed with the fifth portion in the first direction and exposed from the first semiconductor substrate. The second base may include a seventh portion covered with the second semiconductor substrate and an eighth portion disposed with the seventh portion in the first direction and exposed from the second semiconductor substrate. The first terminals and the second terminal may be positioned on the sixth portion. The third terminals and the fourth terminal may be positioned on the eighth portion.

A configuration in which the first and second bases are provided improves the mechanical strength of the radiation detector. Therefore, this configuration reliably achieves a radiation detector having high mechanical strength.

The first aspect may include: a first cover body disposed such that the first semiconductor substrate is positioned between the first cover body and the scintillator; and a second cover body disposed such that the second semiconductor substrate is positioned between the second cover body and the scintillator. Each of the first cover body and the second cover body may include at least one of a light reflector and an electrical insulator.

For example, a configuration in which each of the first cover body and the second cover body includes the light reflector improves light reflection characteristics of scintillation lights. For example, a configuration in which each of the first cover body and the second cover body includes an electrical insulator improves electrical insulation between the radiation detectors adjacent to each other.

In the first aspect, the first wiring member may be disposed on the same side as the scintillator relative to the first semiconductor substrate. The second wiring member may be disposed on the same side as the scintillator relative to the second semiconductor substrate.

In a configuration in which the first wiring member is disposed on the same side as the scintillator relative to the first semiconductor substrate, a substrate for connecting the first wiring member to the first and second electrodes through, for example, die bonding does not need to be provided. In a configuration in which the second wiring member is disposed on the same side as the scintillator relative to the second semiconductor substrate, a substrate for connecting the second wiring member to the first and second electrodes through, for example, die bonding does not need to be provided. Therefore, this configuration more reliably simplifies the configuration of the radiation detector.

In the first aspect, the first wiring member and the second wiring member and the first semiconductor substrate and the second semiconductor substrate may have flexibility. The flexibility of the first wiring member may be higher than the flexibility of the first semiconductor substrate. The flexibility of the second wiring member may be higher than the flexibility of the second semiconductor substrate.

In a configuration in which the flexibility of the first wiring member is higher than the flexibility of the first semiconductor substrate, vibration of the first wiring member tends not to be transmitted to the first semiconductor substrate. A force from the first wiring member tends not to be applied to the first semiconductor substrate, and the first semiconductor substrate tends not to be physically damaged. In a configuration in which the flexibility of the second wiring member is higher than the flexibility of the second semiconductor substrate, vibration of the second wiring member tends not to be transmitted to the second semiconductor substrate. A force from the second wiring member tends not to be applied to the second semiconductor substrate, and the second semiconductor substrate tends not to be physically damaged. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector.

A radiation detector array according to a second aspect includes a plurality of radiation detectors disposed one-dimensionally. Each of the plurality of radiation detectors is the above-described radiation detector. The scintillator further includes a pair of third side surfaces coupling the pair of end surfaces and coupling the first side surface and the second side surface. Any two radiation detectors adjacent to each other of the plurality of radiation detectors are disposed such that the third side surface of the scintillator included in one radiation detector and the third side surface of the scintillator included in another radiation detector oppose each other.

The second aspect realizes the radiation detector array in which the plurality of radiation detectors having high time resolution and high detection sensitivity are one-dimensionally disposed.

In the second aspect, the first semiconductor photodetectors included in the plurality of radiation detectors may be integrally formed. The second semiconductor photodetectors included in the plurality of radiation detectors may be integrally formed.

A configuration in which the above-described first semiconductor photodetectors are integrally formed and the above-described second semiconductor photodetectors are integrally formed improves mechanical strength of the radiation detector array in which the plurality of radiation detectors are one-dimensionally disposed.

The second aspect may include a plurality of radiation detectors two-dimensionally disposed in the matrix. Each of the plurality of radiation detectors disposed in a row direction of the plurality of radiation detectors may be the above-described radiation detector array. Any two radiation detectors adjacent to each other in a column direction of the plurality of radiation detectors may be disposed such that either the first semiconductor photodetector or the second semiconductor photodetector included in one radiation detector and either the first semiconductor photodetector or the second semiconductor photodetector included in the other radiation detector oppose each other in the column direction.

A configuration in which the plurality of radiation detectors are two-dimensionally disposed in the matrix realizes the radiation detector array in which the radiation detectors having high time resolution and high detection sensitivity are two-dimensionally disposed in the matrix.

A radiation detector array according to a third aspect includes a plurality of radiation detectors disposed one-dimensionally. Each of the plurality of radiation detectors is the above-described radiation detector. The scintillator further includes a pair of third side surfaces coupling the pair of end surfaces and coupling the first side surface and the second side surface. Any two radiation detectors adjacent to each other of the plurality of radiation detectors are disposed such that the third side surface of the scintillator included in one radiation detector and either the first semiconductor photodetector or the second semiconductor photodetector included in the other radiation detector oppose each other.

The third aspect realizes the radiation detector array in which the radiation detectors having high time resolution and high detection sensitivity are one-dimensionally disposed.

The third aspect may include a plurality of radiation detectors two-dimensionally disposed in the matrix. Each of the plurality of radiation detectors disposed in a row direction of the plurality of radiation detectors may be the above-described radiation detector array. Any two radiation detectors adjacent to each other in a column direction of the plurality of radiation detectors may be disposed such that the third side surface of the scintillator included in one radiation detector and either the first semiconductor photodetector or the second semiconductor photodetector included in the other radiation detector oppose each other in the column direction.

A configuration in which the plurality of radiation detectors are two-dimensionally disposed in the matrix realizes the radiation detector array in which the radiation detectors having high time resolution and high detection sensitivity are two-dimensionally disposed in the matrix. In a configuration in which the third side surface and either the first semiconductor photodetector or the second semiconductor photodetector included in the other radiation detector oppose each other in the column direction, the plurality of radiation detectors are two-dimensionally disposed in a smaller space as compared with a configuration in which the first semiconductor photodetector and the second semiconductor photodetector oppose each other.

Advantageous Effects of Invention

A first aspect of the present invention provides a radiation detector having high time resolution and high detection sensitivity. Second and third aspects of the present invention provide radiation detector arrays including the radiation detectors having high time resolution and high detection sensitivity.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that, in the description, the same reference numerals will be used for the same elements or elements having the same functions, and redundant description will be omitted.

First Embodiment

A configuration of a radiation detector RD1according to a first embodiment will be described with reference toFIGS.1to10.FIGS.1and2are perspective views illustrating the radiation detector according to the first embodiment.FIG.3is a plan view illustrating a first semiconductor photodetector.FIG.4is a plan view illustrating a second semiconductor photodetector.FIG.5is a diagram illustrating an equivalent circuit of a photodetection region.FIGS.6to8are side views illustrating the radiation detector according to the first embodiment.FIGS.9and10are perspective views illustrating the radiation detector according to the first embodiment. InFIGS.1and9, illustration of a part of the second semiconductor photodetector is omitted for the sake of description. InFIGS.2and10, illustration of a part of the first semiconductor photodetector is omitted for the sake of description.FIGS.9and10illustrate a reinforcement body by a two-dot dashed line.

As illustrated inFIGS.1and2, the radiation detector RD1includes a scintillator1, a semiconductor photodetector10a, a semiconductor photodetector10b, a wiring member30a, and a wiring member30b. The scintillator1generates a scintillation light in response to entry of radiation on the scintillator1. The scintillation light contains, for example, fluorescence. The semiconductor photodetectors10aand10bdetect scintillation lights generated in the scintillator1. The semiconductor photodetector10aincludes a semiconductor substrate11aand is electrically connected to the wiring member30a. The semiconductor photodetector10bincludes a semiconductor substrate11band is electrically connected to the wiring member30b. For example, when the semiconductor photodetector10aconstitutes a first semiconductor photodetector, the semiconductor photodetector10bconstitutes a second semiconductor photodetector. For example, when the wiring member30aconstitutes a first wiring member, the wiring member30bconstitutes a second wiring member. For example, when the semiconductor substrate11aconstitutes a first semiconductor substrate, the semiconductor substrate11bconstitutes a second semiconductor substrate.

The scintillator1includes a pair of end surfaces1aand1bopposing each other, a pair of side surfaces1cand1dopposing each other, and a pair of side surfaces1eand1fopposing each other. The end surfaces1aand1b, the side surfaces1cand1d, and the side surfaces1eand1fconstitute outer surfaces of the scintillator1. The end surfaces1aand1boppose each other in a first direction D1. The end surfaces1aand1bdefine both ends of the scintillator1in the first direction D1. The side surfaces1cand1doppose each other in a second direction D2intersecting the first direction D1and couple the pair of end surfaces1aand1b. In the present embodiment, the second direction D2coincides with a direction orthogonal to the side surface1c. The side surfaces1cand1ddefine both ends of the scintillator1in the second direction D2. The side surfaces1eand1fcouple the end surfaces1aand1band couple the side surface1cand the side surface1d. The side surfaces1eand1foppose each other in a third direction D3intersecting the first direction D1and the second direction D2. The third direction D3corresponds with a direction parallel to the side surface1c. In the present embodiment, the first direction D1, the second direction D2, and the third direction D3are orthogonal to each other. The side surfaces1eand1fdefine both ends of the scintillator1in the third direction D3. For example, when the side surface1cconstitutes a first side surface, the side surface1dconstitutes a second side surface, and the side surfaces1eand1fconstitute a pair of third side surfaces.

The end surface1aand the end surface1bextend in the second direction D2to couple the side surface1cand the side surface1d. The end surface1aand the end surface1bextend in the third direction D3to couple the side surface1eand the side surface1f. The side surface1cand the side surface1dextend in the first direction D1to couple the end surface1aand the end surface1b. The side surface1cand the side surface1dextend in the third direction D3to couple the side surface1eand the side surface1f. The side surface1eand the side surface1fextend in the first direction D1to couple the end surface1aand the end surface1b. The side surface1eand the side surface1fextend in the second direction D2to couple the side surface1cand the side surface1d. The side surface1eand the side surface1fare adjacent to the side surface1c.

A length of the scintillator1in the first direction D1is longer than a length of the scintillator1in the second direction D2. A length of the scintillator1in the first direction D1is longer than a length of the scintillator1in the third direction D3. The first direction D1is a longitudinal direction of the scintillator1. A length of the side surface1cin the first direction D1is longer than a width of the side surface1cin the third direction D3. A length of the side surface1din the first direction D1is longer than a width of the side surface1din the third direction D3.

The end surfaces1aand1beach have a rectangular shape when viewed in directions orthogonal to the end surfaces1aand1b. The side surfaces1cand1deach have a rectangular shape when viewed in directions orthogonal to the side surfaces1cand1d. The side surfaces1eand1feach have a rectangular shape when viewed in directions orthogonal to the side surfaces1eand1f. In the present embodiment, the scintillator1has a rectangular shape when viewed in the first direction D1, and has a rectangular shape when viewed in the second direction D2and the third direction D3. The scintillator1has, for example, a rectangular parallelepiped shape. The length of the scintillator1in the first direction D1is, for example, about 20 mm. The length of the scintillator1in the second direction D2is, for example, about 4 mm. A length of the scintillator1in the third direction D3is, for example, about 4 mm. The “rectangular shape” in this specification includes, for example, a shape in which each corner is chamfered and a shape in which each corner is rounded. The “rectangular parallelepiped shape” in this specification includes a rectangular parallelepiped shape in which corner portions and ridge portions are chamfered and a rectangular parallelepiped shape in which corner portions and ridge portions are rounded.

The semiconductor substrate11ais disposed to oppose the side surface1c. The semiconductor substrate11bis disposed to oppose the side surface1d. The semiconductor substrates11aand11bcontain, for example, Si. The semiconductor substrate11bhas the same configuration and the same function as, for example, the semiconductor substrate11adisposed on the side surface1cexcept that the semiconductor substrate11bis disposed on the side surface1d. The semiconductor substrate11ais disposed on the side surface1cwith an adhesive, for example. The semiconductor substrate11bis disposed on the side surface1dwith an adhesive, for example.

As illustrated inFIG.3, the semiconductor substrate11aincludes a portion21aand a portion22a. In the present embodiment, the portion21ais covered with the side surface1c. The portion22ais exposed from the side surface1c. The portion21aand the portion22aare disposed in the first direction D1. As illustrated inFIG.4, the semiconductor substrate11bincludes a portion21band a portion22b. In the present embodiment, the portion21bis covered with the side surface1d. The portion22bis exposed from the side surface1d. The portion21band the portion22bare disposed in the first direction D1. For example, when the portion21aconstitutes a first portion, the portion22aconstitutes a second portion. For example, when the portion21bconstitutes a third portion, the portion22bconstitutes a fourth portion.

Each of the semiconductor photodetector10aand the semiconductor photodetector10bincludes a plurality of photodetection regions23a,23b,23c, and23d. The plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor photodetector10aare disposed in the portion21a. The plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor photodetector10bare disposed in the portion21b. The plurality of photodetection regions23a,23b,23c, and23dare disposed in the first direction D1. In the present embodiment, the four photodetection regions23a,23b,23c, and23dare disposed. Each of the plurality of photodetection regions23a,23b,23c, and23dincludes at least one avalanche photodiode12and at least one quenching resistor13. In examples illustrated inFIGS.3and4, each of the plurality of photodetection regions23a,23b,23c, and23dincludes a plurality of avalanche photodiodes12and a plurality of quenching resistors13. The avalanche photodiode12receives the scintillation light and generates photoelectrons from the received scintillation light through photoelectric conversion.

In the portion21a, four conductive wires14a,14b,14c, and14dand a conductive wire14eare disposed. In the portion21b, four conductive wires14a,14b,14c, and14dand a conductive wire14eare disposed. The conductive wires14a,14b,14c, and14dconstitute a wiring pattern for signal readout. The conductive wires14a,14b,14c, and14dare patterned in, for example, a grid shape when viewed in the second direction D2. Each of grid-like patterns of the conductive wires14a,14b,14c, and14dsurrounds one photodetection unit15. The one photodetection unit15includes one avalanche photodiode12and one quenching resistor13. The one quenching resistor13is electrically connected in series with the avalanche photodiode12corresponding to the one quenching resistor13. A plurality of photodetection units15are disposed in each of the portion21aand the portion21b. The photodetection units15are two-dimensionally disposed in the matrix, for example. In the examples illustrated inFIGS.3and4, the photodetection regions23a,23b,23c, and23dare in contact with each other. In practice, the photodetection regions23a,23b,23c, and23dmay be in contact with each other or may be separated from each other. One photodetection unit15may be disposed in each of the plurality of photodetection regions23a,23b,23c, and23d. Therefore, each of the plurality of photodetection regions23a,23b,23c, and23dmay include one avalanche photodiode12and one quenching resistor13.

The at least one quenching resistor13are electrically connected in series with one of an anode or a cathode of a corresponding avalanche photodiode12of the at least one avalanche photodiode12. The avalanche photodiode12includes a contact electrode16. The contact electrode16is electrically connected to one of the anode or the cathode. One end of the quenching resistor13is electrically connected in series with the contact electrode16. The other end of each quenching resistor13is electrically connected in series with each of the conductive wires14a,14b,14c, and14dconstituting the wiring pattern. The conductive wires14a,14b,14c, and14dare electrically connected in parallel to the plurality of quenching resistors13, respectively. The conductive wire14eis electrically connected in parallel to the other of the anodes and the cathodes of the plurality of avalanche photodiodes12.

A plurality of electrodes17a,17b,17c, and17dand an electrode18are disposed in each of the portion22aand the portion22b. That is, each of the semiconductor photodetectors10aand10bincludes the electrodes17a,17b,17c, and17dand the electrode18. Each of the electrodes17a,17b,17c, and17dis electrically connected to the at least one quenching resistor13included in the corresponding photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23d, via the conductive wires14a,14b,14c, and14d, respectively. In the examples illustrated inFIGS.3and4, each of the electrodes17a,17b,17c, and17dis electrically connected in parallel to the plurality of quenching resistors13included in the corresponding photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23d, via the conductive wire14a,14b,14c, and14d, respectively. For example, the electrode17ais connected to the photodetection region23avia the conductive wire14a. The electrode17bis connected to the photodetection region23bvia the conductive wire14b. The electrode17cis connected to the photodetection region23cvia the conductive wire14c. The electrode17dis connected to the photodetection region23dvia the conductive wire14d. In a configuration in which the photodetection regions23a,23b,23c, and23deach include one quenching resistor13, the electrodes17a,17b,17c, and17dare electrically connected in series with the one quenching resistor13included in each of the photodetection regions23a,23b,23c, and23dvia the conductive wires14a,14b,14c, and14d, respectively.

The electrode18is electrically connected to the other of the anode or the cathode of the avalanche photodiode12included in the corresponding photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23dvia the conductive wire14e. In the examples illustrated inFIGS.3and4, the electrode18is electrically connected in parallel to the other of the anodes and the cathodes of the plurality of avalanche photodiodes12via the conductive wire14e. In a configuration in which each of the photodetection regions23a,23b,23c, and23dincludes one avalanche photodiode12, the electrode18is electrically connected in parallel to the other of the anode and the cathode of the one avalanche photodiode12included in each of the photodetection regions23a,23b,23c, and23d, via the conductive wire14e.

The electrodes17a,17b,17c, and17dand the electrode18contain, for example, aluminum or an aluminum composite. The aluminum composite contains, for example, AlSi, AlCu, or AlSiCu. The electrodes17a,17b,17c, and17dand the electrode18are formed by, for example, a plating method, a vapor deposition method, or a sputtering method.

The electrical resistivity of the quenching resistor13is higher than the electrical resistivity of the electrodes17a,17b,17c, and17dand the electrode18. The quenching resistor13contains, for example, polysilicon. A material of the quenching resistor13may include, for example, SiCr, NiCr, or FeCr. The quenching resistor13is formed by, for example, a chemical vapor deposition (CVD) method or a sputtering method. For example, in the semiconductor photodetector10a, when the electrodes17a,17b,17c, and17dconstitute a first electrode, the electrode18constitutes a second electrode. For example, in the semiconductor photodetector10b, when the electrodes17a,17b,17c, and17dconstitute a third electrode, the electrode18constitutes a fourth electrode.

In the present embodiment, each of the at least one quenching resistor13is electrically connected to, for example, the anode of the corresponding avalanche photodiode12of the at least one avalanche photodiode12. In this case, the electrode18is electrically connected to the cathodes of the plurality of avalanche photodiodes12. The at least one quenching resistor13may be electrically connected to the cathode of the corresponding avalanche photodiode12of the at least one avalanche photodiode12. In this case, the electrode18is electrically connected to the anodes of the at least one avalanche photodiode12.

Each avalanche photodiode12is arranged to operate in Geiger mode. In Geiger mode, a reverse bias voltage is applied to the avalanche photodiode12. The reverse bias voltage is, for example, a reverse voltage higher than a breakdown voltage of the avalanche photodiode12. For example, a potential V1is applied to the anode of the avalanche photodiode12, and a potential V2positive relative to the potential V1is applied to the cathode of the avalanche photodiode12. These potentials have relative polarities, and for example, one of the potentials may be a ground potential. The photodetection units15are electrically connected in parallel.

Each of the avalanche photodiodes12may be a so-called reach-through avalanche photodiode or a so-called reverse avalanche photodiode. The reach-through avalanche photodiode12is included in, for example, the radiation detector RD1including the scintillator1that generates the scintillation light having a long wavelength. For example, the reach-through avalanche photodiode is used when the scintillation light is a long-wavelength ray. The reverse avalanche photodiode12is used, for example, when the scintillation light is a short-wavelength ray. The reach-through or reverse avalanche photodiode12is arranged to operate in Geiger mode. The radiation detector RD1may include an avalanche photodiode12operating in a linear mode. The avalanche photodiode12operating in the linear mode may be a so-called reach-through avalanche photodiode or a so-called reverse avalanche photodiode.

On each of the semiconductor substrates11aand11b, for example, the conductive wires14a,14b,14c, and14d, the conductive wire14e, the electrodes17a,17b,17c, and17dconnected to the conductive wires14a,14b,14c, and14d, respectively, and the electrode18connected to the conductive wire14eare disposed. On the semiconductor substrates11aand11b, for example, an insulating layer19is disposed on the conductive wires14a,14b,14c, and14dand the conductive wire14e. In the semiconductor substrate11a, the insulating layer19extends over the portion21aand the portion22a. In the semiconductor substrate11b, the insulating layer19extends over the portion21band the portion22b. In the portions22aand22b, the electrodes17a,17b,17c, and17dand the conductive wires14a,14b,14c, and14dare insulated from the electrode18and the conductive wire14ewith the insulating layer19. In the portions21aand21b, the insulating layer19is formed on the plurality of photodetection units15. The insulating layer19contains, for example, SiO2or SiN. The insulating layer19is formed by, for example, a thermal oxidation method, a sputtering method, or a CVD method.

As illustrated inFIGS.1,2, and6, the wiring member30ais disposed on the same side as the scintillator1relative to the semiconductor substrate11a, for example. At least a part of the wiring member30aand the scintillator1are disposed in front of the same surface of the semiconductor substrate11a, for example. The wiring member30a, the semiconductor substrate11a, and the scintillator1are disposed on a surface11c. The wiring member30bis disposed on the same side as the scintillator1relative to the semiconductor substrate11b. At least a part of the wiring member30band the scintillator1are disposed in front of the same surface of the semiconductor substrate11b, for example. The wiring member30b, the semiconductor substrate11b, and the scintillator1are disposed on a surface11e. The wiring member30bhas the same configuration and the same function as, for example, the wiring member30aelectrically connected to the semiconductor substrate11aexcept that the wiring member30bis electrically connected to the semiconductor substrate11b.

Each of the wiring members30aand30bincludes conductors31a,31b,31c, and31dand a conductor32. The conductors31a,31b,31c, and31dincluded in the wiring member30aare electrically connected to the electrodes17a,17b,17c, and17dincluded in the semiconductor photodetector10a, respectively. The conductors31a,31b,31c, and31dincluded in the wiring member30bare electrically connected to the electrodes17a,17b,17c, and17dincluded in the semiconductor photodetector10b, respectively. The conductor32included in the wiring member30ais electrically connected to the electrode18included in the semiconductor photodetector10a. The conductor32included in the wiring member30bis electrically connected to the electrode18included in the semiconductor photodetector10b. The conductors31a,31b,31c, and31dincluded in the wiring member30aare electrically connected to the electrodes17a,17b,17c, and17dincluded in the semiconductor photodetector10avia a corresponding conductive bump33. The conductors31a,31b,31c, and31dincluded in the wiring member30bare electrically connected to the electrodes17a,17b,17c, and17dincluded in the semiconductor photodetector10bvia the corresponding conductive bump33, for example. The conductor32included in the wiring member30ais connected to the electrode18included in the semiconductor photodetector10avia the conductive bump33, for example. The conductor32included in the wiring member30bis connected to the electrode18included in the semiconductor photodetector10bvia the conductive bump33, for example. The conductive bump33includes, for example, solder, an anisotropic conductive film (ACF), or an anisotropic conductive paste (ACP). The solder includes, for example, Sn—Ag—Cu solder. The conductive bump33may include, for example, an Au bump, an Ni bump, or a Cu bump.

In the present embodiment, when the radiation detector RD1is driven, the potential V1is applied to the anodes of the avalanche photodiodes12via the conductors31a,31b,31c, and31d, and the potential V2is applied to the cathodes of the avalanche photodiodes12via the conductor32. The potential V1may be applied to the cathodes of the avalanche photodiodes12via the conductor32, and the potential V2may be applied to the anodes of the avalanche photodiodes12via the conductors31a,31b,31c, and31d. InFIG.3, only the conductor31ais depicted. The conductors31a,31b,31c, and31dand the conductor32contain, for example, Al, Cu, Cu/Ni/Au, or Cu/Ni/Pd/Au. The conductors31a,31b,31c, and31dand the conductor32are formed by, for example, a sputtering method or a plating method.

The wiring member30aand the wiring member30b, and the semiconductor substrate11aand the semiconductor substrate11bhave flexibility. The flexibility of the wiring member30ais higher than the flexibility of the semiconductor substrate11a. The flexibility of the wiring member30bis higher than the flexibility of the semiconductor substrate11b. The flexibility of the wiring member30aand the flexibility of the wiring member30bare equal to each other, for example. The flexibility of the wiring member30aand the flexibility of the wiring member30bmay be different from each other.

When viewed in the second direction D2, one region including the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11ais formed along an outline of the side surface1c. Therefore, a plurality of edges constituting the outline of the photodetection regions23a,23b,23c, and23dare formed along a corresponding edge of the plurality of edges of the outline of the side surface1cwhen viewed in the second direction D2. When viewed in the second direction D2, one region formed by the outline of the plurality of photodetection regions23a,23b,23c, and23dhas a shape corresponding to an outline shape of the side surface1c. In the semiconductor substrate11a, the photodetection units15are disposed such that the one region including the photodetection regions23a,23b,23c, and23dhas the outline shape corresponding to the outline shape of the side surface1c, when viewed in the second direction D2. Each of the photodetection regions23a,23b,23c, and23dhas, for example, a rectangular outline shape corresponding to the outline shape of the side surface1c.

When viewed in the second direction D2, one region including the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11bis formed along an outline of the side surface1d. A plurality of edges constituting the outline of the photodetection regions23a,23b,23c, and23dare formed along a corresponding edge of a plurality of edges of the outline of the side surface1dwhen viewed in the second direction D2. When viewed in the second direction D2, one region formed by the outline of the plurality of photodetection regions23a,23b,23c, and23dhas a shape corresponding to an outline shape of the side surface1d. In the semiconductor substrate11b, the photodetection units15are disposed such that the one region including the photodetection regions23a,23b,23c, and23dhas the outline shape corresponding to the outline shape of the side surface1d, when viewed in the second direction D2. Each of the photodetection regions23a,23b,23c, and23dhas, for example, a rectangular outline shape corresponding to the outline shape of the side surface1d.

In the examples illustrated inFIGS.3and4, in the plurality of photodetection regions23a,23b, and23c, three photodetection units15are disposed in each column in the first direction D1, and three photodetection units15are disposed in each column in the third direction D3. The photodetection region23aincludes a total of nine photodetection units15. In the photodetection region23d, five photodetection units15are disposed in each column in the first direction D1, and three photodetection units15are disposed in each column in the third direction D3. The photodetection region23dincludes a total of fifteen photodetection units15.

The photodetection regions23a,23b,23c, and23dare disposed in the first direction D1, for example. In the present embodiment, the photodetection region23a, the photodetection region23b, the photodetection region23c, and the photodetection region23dare disposed in this order. The photodetection region23dis closer to the portion22aor22bthan the photodetection region23a, the photodetection region23b, and the photodetection region23c. The photodetection region23cis closer to the portion22aor22bthan the photodetection region23aand the photodetection region23b. The photodetection region23bis closer to the portion22aor22bthan the photodetection region23a. In the present embodiment, a width of the conductive wire14ais larger than any widths of the conductive wires14b,14c, and14d. The width of the conductive wire14bis larger than any widths of the conductive wires14cand14d. The width of the conductive wire14cis larger than the width of the conductive wire14d. For example, when viewed in the second direction D2, the conductive wire14aand the conductive wires14band14cextend between both ends of the semiconductor substrate11aor11bin the third direction D3and the photodetection regions23a,23b,23c, and23d. When viewed in the second direction D2, the conductive wire14dis disposed, for example, between the conductive wire14aand the conductive wires14band14c. The conductive wires14a,14b,14c, and14dextend in the first direction D1. The widths of the conductive wires14a,14b,14c, and14dare widths in a direction perpendicular to an extending direction of the conductive wires14a,14b,14c, and14d. The widths of the conductive wires14a,14b,14c, and14dare widths in the third direction D3. For example, when the photodetection region23aconstitutes a first photodetection region, the photodetection region23dconstitutes a second photodetection region.

As illustrated inFIGS.1and2, the radiation detector RD1includes, for example, a reinforcement body45. For example, the reinforcement body45is disposed between the portion22aand the portion22b. In the present embodiment, the reinforcement body45covers the portion22aand the portion22b, and couples the portion22aand the portion22b. The reinforcement body45is in contact with the portion22aand the portion22band the scintillator1, for example. The reinforcement body45includes, for example, surfaces45a,45b, and45c. The surfaces45a,45b, and45care exposed from the portion22aand the portion22band the scintillator1, for example. The surface45aoppose the end surface1bin the first direction D1, for example. The surfaces45band45coppose each other in the third direction D3, for example.

The reinforcement body45contains, for example, a resin. For example, the resin of the reinforcement body45fills a space demarcated by the portion22aand the portion22band the scintillator1. The resin of the reinforcement body45contains, for example, a thermosetting resin. The resin of the reinforcement body45contains, for example, an epoxy resin, a silicone resin, an acrylic resin, a polyimide resin, a phenol resin, or a para-xylylene-based polymer.

In the present embodiment, the reinforcement body45includes, for example, a block. The block of the reinforcement body45has, for example, a shape corresponding to the space demarcated by the portion22aand the portion22band the scintillator1. The block of the reinforcement body45includes, for example, a recess formed not to interfere with the wiring member30aand the wiring member30b. The block of the reinforcement body45is disposed between the portions22aand22b, for example. In the present embodiment, the block of the reinforcement body45is fixed to the portion22aand the portion22bwith, for example, an adhesive. The adhesive contains, for example, an epoxy resin, a silicone resin, an acrylic resin, a polyimide resin, or a phenol resin.

The block of the reinforcement body45contains, for example, metal. The metal block contains, for example, Al, a titanium alloy, a nickel alloy, or stainless steel. The block of the reinforcement body45includes, for example, a glass block. The glass block contains, for example, quartz glass or borosilicate glass. The block of the reinforcement body45includes, for example, a ceramic block. The ceramic block includes, for example, alumina, silicon nitride, silicon carbide, sapphire, zirconia, cordierite, yttria, aluminum nitride, cermet, mullite, steatite, or forsterite. The block of the reinforcement body45includes, for example, a resin block. The resin block contains, for example, an epoxy resin, a silicone resin, an acrylic resin, a polyimide resin, a phenol resin, or a para-xylylene-based polymer.

As illustrated inFIG.6, the semiconductor substrate11aincludes the surface11cand a surface11dopposing each other in the second direction D2. The surface11coppose the scintillator1in the second direction D2. The surface11doppose the surface11cin the second direction D2. In the present embodiment, one of the anode and the cathode of each of the avalanche photodiodes12is disposed at the surface11c, and the other of the anode and the cathode of each of the avalanche photodiodes12is disposed at the surface11d. For example, when the surface11cconstitutes the first surface, the surface11dconstitutes the second surface.

The semiconductor substrate11bincludes the surface11eand a surface11fopposing each other in the second direction D2. The surface11eoppose the scintillator1in the second direction D2. The surface11foppose the surface11ein the second direction D2. In the present embodiment, one of the anode and the cathode of each of the avalanche photodiodes12is disposed at the surface11e, and the other of the anode and the cathode of each of the avalanche photodiodes12is disposed at the surface11f. For example, when the surface11econstitutes the third surface, the surface11fconstitutes the fourth surface.

The surfaces11dand11finclude, for example, polished surfaces. For example, after the semiconductor substrates11aand11bare disposed on the scintillator1, and the reinforcement body45is disposed between the portion22aand the portion22b, the surfaces11dand11fare polished.FIG.7is a side view illustrating the radiation detector RD1before the surfaces11dand11fare polished.FIG.8is a side view illustrating the radiation detector RD1after the surfaces11dand11fare polished. As illustrated inFIGS.7and8, in the present embodiment, the surface11dis polished such that the semiconductor substrate11ais thinned, and the surface11fis polished such that the semiconductor substrate11bis thinned.

The surfaces11dand11fare mechanically polished, for example. The surfaces11dand11fare mechanically polished by, for example, a grinding method, a lapping method, or a dry polishing method with a polishing foil. The surfaces11dand11fmay be mechanochemically polished. The surfaces11dand11fare chemically polished, for example, by wet polishing with a CMP slurry. In the configuration in which the surfaces11dand11finclude polished surfaces, the thicknesses of the semiconductor substrates11aand11bare, for example, 10 to 200 μm. Surface roughness of the polished surfaces is, for example, 0.001 to 200 μm. In this specification, surface roughness of a surface is represented by a maximum height (Rz). The maximum height (Rz) is defined in JIS B 0601:2001 (ISO 4287:1997). Before the surfaces11dand11fare polished, the thicknesses of the semiconductor substrates11aand11bare, for example, 250 to 1,000 μm.

As illustrated inFIGS.1and6, the radiation detector RD1includes, for example, a cover body47a. The cover body47ais disposed such that the semiconductor substrate11ais positioned between the cover body47aand the scintillator1. In the present embodiment, the cover body47ais disposed on the surface11d. The cover body47ais disposed on at least a part of the surface11d. The cover body47amay be disposed on the entire surface11d. Therefore, the cover body47amay be disposed only in a region of the surface11dcorresponding to the portion21a, or may be disposed in the entire region of the surface11dcorresponding to the portion21aand the portion22a.FIGS.1and6illustrate an example in which the cover body47ais disposed in the entire region of the surface11dcorresponding to the portion21aand the portion22a. The radiation detector RD1does not need to include the cover body47a.

As illustrated inFIGS.2and6, the radiation detector RD1includes, for example, a cover body47b. The cover body47bis disposed such that the semiconductor substrate11bis positioned between the cover body47band the scintillator1. In the present embodiment, the cover body47bis disposed on the surface11f. The cover body47bis disposed on at least a part of the surface11f. The cover body47bmay be disposed on the entire surface11f. Therefore, the cover body47bmay be disposed only in a region of the surface11fcorresponding to the portion21b, or may be disposed in the entire region of the surface11fcorresponding to the portion21band the portion22b.FIGS.2and6illustrate an example in which the cover body47bis disposed in the entire region of the surface11fcorresponding to the portion21band the portion22b. The radiation detector RD1does not need to include the cover body47b. For example, when the cover body47aconstitutes the first cover body, the cover body47bconstitutes the second cover body.

Each of the cover bodies47aand47bincludes, for example, a light reflector48. The light reflector48includes, for example, a film. The film is made of metal, for example. Examples of the metal include Al, Ag, Ti, Pt, Ni, or Au. The light reflector48includes, for example, a metallic thin film. The light reflector48may include a multilayer optical film or a Teflon (registered trademark) film. The light reflector48is formed by, for example, a plating method, a vapor deposition method, or a sputtering method. A thickness of the light reflector48is, for example, 0.05 to 100 μm.

The cover bodies47aand47binclude, for example, an electrical insulator49. The electrical insulator49includes, for example, a film. The film includes, for example, an electrical insulating material. Examples of the electrical insulating material include a silicon compound, an epoxy resin, a silicone resin, an acrylic resin, a polyimide resin, a phenol resin, or a para-xylylene-based polymer. The electrical insulator49includes, for example, an electrical insulating thin film. Examples of the silicon compound include SiO2or SiN. Examples of the polymer include a para-xylylene-based polymer. The electrical insulator49is formed by, for example, a chemical vapor deposition (CVD) method, a thermal oxidation method, a sputtering method, a vapor deposition method, or a potting method. The electrical insulator49included in the cover body47amay be formed by, for example, winding an electrical insulation film around the semiconductor substrate11adisposed on the scintillator1. The electrical insulator49included in the cover body47bmay be formed by, for example, winding an electrical insulation film around the semiconductor substrate11bdisposed on the scintillator1. A thickness of the electrical insulator49is, for example, 0.05 to 100 μm.

Each of the cover bodies47aand47bincludes, for example, the light reflector48and the electrical insulator49. Each of the cover bodies47aand47bhas, for example, a two-layer structure including the light reflector48and the electrical insulator49. In a configuration in which the cover bodies47aand47bhave the two-layer structure, the light reflector48may be disposed between the semiconductor substrate11aand the electrical insulator49, and the electrical insulator49may be disposed between the semiconductor substrate11aand the light reflector48. The light reflector48may be disposed between the semiconductor substrate11band the electrical insulator49, and the electrical insulator49may be disposed between the semiconductor substrate11band the light reflector48. In the present embodiment, each of the cover bodies47aand47bincludes at least one of the light reflector48and the electrical insulator49. The cover bodies47aand47bhave, for example, a single-layer structure including only one of the light reflector48and the electrical insulator49. The cover bodies47aand47bmay have, for example, characteristics of a light reflector and characteristics of an electrical insulator.FIG.6illustrates an example in which the electrical insulators49are disposed between the semiconductor substrate11aand the light reflector48and between the semiconductor substrate11band the light reflector48.

The cover body47ais disposed on the surface11d, for example. The cover body47ais disposed, for example, on the entire surface11dand on a side surface11g. The side surface11gcouples the surface11cand the surface11dto each other in the second direction D2, for example. The side surface11gconstitutes, for example, an outer circumferential edge of the cover body47awhen viewed in the second direction D2. The light reflector48may be disposed on the entire surface11d, and the electrical insulator49may be disposed on the side surface11gand on the light reflector48disposed on the surface11d. The cover body47bis disposed on the surface11f, for example. The cover body47bis disposed, for example, on the entire surface11fand on a side surface11h. The side surface11hcouples the surface11eand the surface11fto each other in the second direction D2. The side surface11hconstitutes, for example, an outer circumferential edge of the cover body47bwhen viewed in the second direction D2. The light reflector48may be disposed on the entire surface11f, and the electrical insulator49may be disposed on the side surface11hand on the light reflector48disposed on the surface11f.

In the present embodiment, in a configuration in which a potential of the anode or the cathode of each of the avalanche photodiodes12at the surface11dis the ground potential, the electrical insulator49does not need to be disposed on the surface11d. In a configuration in which a potential of the anode or the cathode of each of the avalanche photodiodes12at the surface11dis not the ground potential, the electrical insulator49may be disposed on the surface11d. In a configuration in which a potential of the anode or the cathode of each of the avalanche photodiodes12at the surface11fis the ground potential, the electrical insulator49does not need to be disposed on the surface11f. In a configuration in which a potential of the anode or the cathode of each of the avalanche photodiodes12at the surface11fis not the ground potential, the electrical insulator49may be disposed on the surface11f.

As illustrated inFIGS.9and10, the radiation detector RD1includes, for example, a base40aand a base40b. The base40aincludes a surface40cand a surface40dopposing each other in the second direction D2. The base40ais disposed such that the semiconductor substrate11ais positioned between the surface40cand the scintillator1. Therefore, at least a part of the wiring member30aand the scintillator1are disposed in front of the same surface of the base40a, for example. The base40bincludes a surface40eand a surface40fopposing each other in the second direction D2. The base40bis disposed such that the semiconductor substrate11bis positioned between the surface40eand the scintillator1. Therefore, at least a part of the wiring member30band the scintillator1are disposed in front of the same surface of the base40b, for example. The base40bhas, for example, the same configuration and the same function as the base40a. For example, when the base40aconstitutes a first base, the base40bconstitutes a second base. For example, when the surface40cconstitutes a fifth surface, the surface40dconstitutes a sixth surface. For example, when the surface40econstitutes a seventh surface, the surface40fconstitutes an eighth surface.

The base40aincludes a portion51aand a portion52a. The portion51ais covered with the semiconductor substrate11a. The portion52ais exposed from the semiconductor substrate11a. The portion51aand the portion52aare disposed in the first direction D1. The base40bincludes a portion51band a portion52b. The portion51bis covered with the semiconductor substrate11b. The portion52bis exposed from the semiconductor substrate11b. The portion51band the portion52bare disposed in the first direction D1. For example, when the portion51aconstitutes a fifth portion, the portion52aconstitutes a sixth portion. For example, when the portion51bconstitutes a seventh portion, the portion52bconstitutes an eighth portion.

The radiation detector RD1includes, for example, terminals41a,41b,41c, and41d, terminals42, wires43, and wires44. On the base40a, the terminals41a,41b,41c, and41dand the terminal42are disposed on the surface40c. The terminals41a,41b,41c, and41dand the terminal42are disposed, for example, on the same side as the scintillator1relative to the semiconductor substrate11a. That is, the terminals41a,41b,41c, and41dand the scintillator1are disposed in front of the same surface of the corresponding base40a. The terminal42and the scintillator1are disposed in front of the same surface of the corresponding base40a. The terminals41a,41b,41c, and41ddisposed on the base40aare positioned on the portion52aand are electrically connected to the electrode17included in the semiconductor photodetector10athrough the wire43. The terminal42disposed on the base40ais positioned on the portion52aand is electrically connected to the electrode18included in the semiconductor photodetector10athrough the wire44.

The wires43and44are covered and protected with, for example, the resin of the reinforcement body45. The wiring member30ais electrically connected to the electrodes17a,17b,17c, and17dand the electrode18included in the semiconductor photodetector10avia the corresponding conductive bump46. On the base40a, for example, when the terminals41a,41b,41c, and41dconstitute a first terminal, the terminal42constitutes a second terminal. On the base40a, for example, when the wire43constitutes a first wire, the wire44constitutes a second wire. The wires43and44may be protected with the block of reinforcement body45, for example.

On the base40b, the terminals41a,41b,41c, and41dand the terminal42are disposed on the surface40e. The terminals41a,41b,41c, and41dand the terminal42are disposed, for example, on the same side as the scintillator1relative to the semiconductor substrate11b. That is, the terminals41a,41b,41c, and41dand the scintillator1are disposed in front of the same surface of the corresponding base40b. The terminal42and the scintillator1are disposed in front of the same surface of the corresponding base40b. The terminals41a,41b,41c, and41ddisposed on the base40bare positioned on the portion52band are electrically connected to the electrodes17a,17b,17c, and17dincluded in the semiconductor photodetector10bthrough the wire43. The terminal42disposed on the base40bis positioned on the portion52band is electrically connected to the electrode18included in the semiconductor photodetector10bthrough the wire44.

The wires43and44are covered and protected with, for example, the resin of the reinforcement body45. The wiring member30bis electrically connected to the electrodes17a,17b,17c, and17dand the electrode18included in the semiconductor photodetector10bvia the corresponding conductive bump46. On the base40b, for example, when the terminals41a,41b,41c, and41dconstitute a third terminal, the terminal42constitutes a fourth terminal. On the base40b, for example, when the wire43constitutes a third wire, the wire44constitutes a fourth wire. In the present embodiment, the terminals41a,41b,41c, and41dof the base40bhave the same configuration and function as the terminals41a,41b,41c, and41dof the base40a, and the terminal42of the base40bhas the same configuration and function as the terminal42of the base40a. The radiation detector RD1does not need to include one of the base40aand the base40b, and does not need to include the base40aand the base40b. The wires43and44may be protected with the block of reinforcement body45, for example.

The radiation detector RD1includes, for example, resins55. The resins55cover the wire43and the wire44individually or cover both the wire43and the wire44. In the configuration in which the resins55cover the wire43and the wire44individually, the resins55may be separated from each other or connected to each other. In this specification, that the “resin55covers the wire43” also means that the resin covers both a connection position between the terminals41and the wire43and a connection position between the electrodes17a,17b,17c, and17dand the wire43. In addition, that the “resin55covers the wire44” also means that the resin covers both a connection position between the terminal42and the wire44and a connection position between the electrode18and the wire44. In the present embodiment, the resin of the reinforcement body45is disposed between the portion22aand the portion22b, for example, to cover the resins55. The radiation detector RD1does not need to include the resins55.FIGS.9and10illustrate an example in which the radiation detector RD1includes the resins55. The block of reinforcement body45may be disposed between the portions22aand22bto cover the resins55.

The configuration in which the radiation detector RD1includes the base40aincludes, for example, the cover body47a. The cover body47ais disposed on the surface40d. In this configuration, the scintillator1, the semiconductor substrate11a, the base40a, and the cover body47aare disposed in the order of the scintillator1, the semiconductor substrate11a, the base40a, and the cover body47a. Therefore, the cover body47ais disposed such that the semiconductor substrate11aand the base40aare positioned between the cover body47aand the scintillator1. The configuration in which the radiation detector RD1includes the base40bincludes, for example, the cover body47b. The cover body47bis disposed on the surface40f. In this configuration, the scintillator1, the semiconductor substrate11b, the base40b, and the cover body47bare disposed in the order of the scintillator1, the semiconductor substrate11b, the base40b, and the cover body47b. Therefore, the cover body47bis disposed such that the semiconductor substrate11band the base40bare positioned between the cover body47band the scintillator1. The radiation detector RD1does not need to include at least one of the cover body47aand the cover body47b.

As illustrated inFIGS.1,2, and6, the radiation detector RD1includes, for example, a light reflector56. For example, the light reflector56is disposed on at least one of the end surfaces1aand1band the side surfaces1eand1fof the scintillator1. In the present embodiment, the light reflectors56are disposed on all of the end surfaces1aand1band the side surfaces1eand1f. The light reflector56reflects the scintillation light such that the scintillation light incident on the end surfaces1aand1band the side surfaces1eand1fis not emitted outside the scintillator1. A material and a thickness of the light reflector56are, for example, the same as the material and thickness of the light reflector48. For example, the light reflector56is formed by the same method as the light reflector48. The radiation detector RD1does not need to include the light reflector56.

A radiation detector RD1according to a modification example of the first embodiment will be described with reference toFIGS.11and12.FIG.11is a perspective view illustrating the radiation detector RD1according to the modification example of the first embodiment.FIG.12is a view illustrating paths of some scintillation lights.FIG.12illustrates the paths of some scintillation lights when the scintillator1is viewed in the third direction D3. The radiation detector RD1according to the present modification example has the same configuration as the radiation detector RD1according to the first embodiment except for a configuration of the scintillator1.

As illustrated inFIG.11, the scintillator1according to the modification example includes a plurality of portions1p,1q,1r, and1s. Each of the plurality of portions1p,1q,1r, and1sis positioned corresponding to the photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23ddisposed in each of the semiconductor substrate11aand the semiconductor substrate11b. The plurality of portions1p,1q,1r, and1scorrespond to a plurality of photodetection regions23a,23b,23c, and23d, respectively. The portion1pcorresponds to the photodetection region23a. The portion1qcorresponds to the photodetection region23b. The portion1rcorresponds to the photodetection region23c. The portion1scorresponds to the photodetection region23d. The plurality of portions1p,1q,1r, and1sare disposed independently of each other.

The portions1p,1q,1r, and1sinclude a pair of opposing surfaces3aand3bthat oppose each other, a pair of coupling surfaces3cand3dthat oppose each other, and a pair of coupling surfaces3eand3fthat oppose each other. The opposing surfaces3aand3b, the coupling surfaces3cand3d, and the coupling surfaces3eand3fconstitute outer surfaces of the portions1p,1q,1r, and1s. The opposing surfaces3aand3boppose each other in the first direction D1. The first direction D1is a longitudinal direction of the scintillator1. The coupling surfaces3cand3doppose each other in the second direction D2. The coupling surface3doppose the coupling surface3cin the second direction D2. The second direction D2coincides with a direction orthogonal to the coupling surface3c. The coupling surfaces3eand3foppose each other in the third direction D3. In the present modification example, the opposing surface3aof the portion1pcoincides with the end surface1aof the scintillator1. The opposing surface3bof the portion1scoincides with the end surface1bof the scintillator1. The coupling surfaces3cof the portions1p,1q,1r, and1sall constitute a side surface1cof the scintillator1. The coupling surfaces3dof the portions1p,1q,1r, and1sall constitute a side surface1dof the scintillator1. The coupling surfaces3eof the portions1p,1q,1r, and1sall constitute a side surface1eof the scintillator1. The coupling surfaces3fof the portions1p,1q,1r, and1sall constitute a side surface1fof the scintillator1. For example, when the coupling surface3cconstitutes the first coupling surface, the coupling surface3dconstitutes a second coupling surface.

The opposing surface3aand the opposing surface3bextend in the second direction D2to couple the coupling surface3cand the coupling surface3d. The opposing surface3aand the opposing surface3bextend in the third direction D3to couple the coupling surface3eand the coupling surface3f. The coupling surface3cand the coupling surface3dextend in the first direction D1to couple the opposing surface3aand the opposing surface3b. The coupling surface3cand the coupling surface3dextend in the third direction D3to couple the coupling surface3eand the coupling surface3f. The coupling surface3eand the coupling surface3fextend in the first direction D1to couple the opposing surface3aand the opposing surface3b. The coupling surface3eand the coupling surface3fextend in the second direction D2to couple the coupling surface3cand the coupling surface3d. The coupling surface3eand the coupling surface3fare adjacent to the coupling surface3c.

In the present modification example, the opposing surfaces3aand3beach have, for example, a rectangular shape when viewed in directions orthogonal to the opposing surfaces3aand3b. The coupling surfaces3cand3deach have, for example, a rectangular shape when viewed in directions orthogonal to the coupling surfaces3cand3d. The coupling surfaces3eand3feach have, for example, a rectangular shape when viewed in directions orthogonal to the coupling surfaces3eand3f. The portions1p,1q,1r, and1shave a rectangular shape when viewed in the second direction D2and the third direction D3. The portions1p,1q,1r, and1shave a rectangular shape when viewed in the first direction D1.

In the present modification example, the portions1p,1q,1r, and1sare disposed in the first direction D1. A length of the portions1p,1q,1r, and1sin the first direction D1is, for example, about 0.05 to 100 mm. A length of the portions1p,1q,1r, and1sin the second direction D2are, for example, about 0.05 to 20 mm. A length of the portions1p,1q,1r, and1sin the third direction D3are, for example, about 0.05 to 20 mm. The portions1p,1q,1r, and1smay have different sizes. For example, of the plurality of portions1p,1q,1r, and1s, some portions1p,1q, and1rmay have substantially the same size, and another portion1smay have a different size from that of the portions1p,1q, and1r. Some portions1pand1qmay have substantially the same size, and the other portions1rand1smay be different from the portions1pand1qand have substantially the same size. The portions1p,1q,1r, and1smay have substantially the same size.

A total length of the portions1p,1q,1r, and1sin the first direction D1is longer than a length of each of the portions1p,1q,1r, and1sin the second direction D2. Therefore, the total length of the portions1p,1q,1r, and1sin the first direction D1is longer than the length of any portion1p,1q,1r, or1shaving the maximum length in the second direction D2of the portions1p,1q,1r, and1s. The total length of the portions1p,1q,1r, and1sin the first direction D1is longer than the length of any portion1p,1q,1r, or1shaving the maximum length in the third direction D3of the portions1p,1q,1r, and1s.

The portions1p,1q,1r, and1scontain, for example, the same material as that of the scintillator1according to the first embodiment. The portions1p,1q,1r, and1scontain, for example, the same material. The portions1p,1q,1r, and1smay contain different materials from each other, of the materials contained in the scintillator1according to the first embodiment. Therefore, of the materials of the scintillator1according to the first embodiment, for example, the portions1pand1rmay contain the same material, and the portions1qand1smay contain the same material. In this case, the material contained in the portions1pand1ris different from the material contained in the portions1qand1s.

The portions1p,1q,1r, and1sare joined to each other, for example. The opposing surface3bof the portion1pis joined to the opposing surface3aof the portion1q, for example. The opposing surface3bof the portion1qis joined to the opposing surface3aof the portion1r, for example. The opposing surface3bof the portion1ris joined to the opposing surface3aof the portion1s, for example. The joining between the portion1pand the portion1q, the joining between the portion1qand the portion1r, and the joining between the portion1rand the portion1sare performed by, for example, an adhesive.

The radiation detector RD1according to the present modification example includes, for example, light reflecting members24. The light reflecting members24are disposed, for example, between the plurality of portions1p,1q,1r, and1s. The portion1p, the portion1q, the portion1r, and the portion1sare joined to each other via the light reflecting members24, for example. The light reflecting members24are disposed at positions that are at least one of a position between the portion1pand the portion1q, a position between the portion1qand the portion1r, and a position between the portion1rand the portion1s. The joining between the portion1pand the portion1q, the joining between the portion1qand the portion1r, and the joining between the portion1rand the portion1svia the corresponding light reflecting member24are performed by, for example, an adhesive.

In the present modification example, the portion1p, the portion1q, the portion1r, and the portion1smay be separately disposed in the first direction D1. When the portion1p, the portion1q, the portion1r, and the portion1sare individually separated from each other, for example, atmosphere is present between the portion1pand the portion1q, between the portion1qand the portion1r, and between the portion1rand the portion1s. When the portion1p, the portion1q, the portion1r, and the portion1sare individually separated from each other, the light reflecting member24may be provided on at least one of the opposing surfaces3aand3bof the portions1p,1q,1r, and1s. In each of the portions1p,1q,1r, and1s, the light reflecting members24may be disposed on both of the opposing surfaces3aand3b. The light reflecting member24may be disposed on any one of the opposing surfaces3aand3bof each of the portions1p,1q,1r, and1s. Of the portion1p, the portion1q, the portion1r, and the portion1s, for example, the portion1pand the portion1qmay be joined to each other, and the portion1pand the portion1qjoined to each other may be separated from the portion1rand the portion1s.

The light reflecting member24includes, for example, metal, a multilayer optical film, or Teflon (registered trademark). The metal of the light reflecting member24includes, for example, Al, Ag, or Au. The light reflecting member24is formed by, for example, a plating method, a vapor deposition method, or a sputtering method. A thickness of the light reflecting member24is, for example, 0.05 to 100 μm. The light reflecting member24can transmit radiation incident on the scintillator1. The material and thickness of the light reflecting member24are the same as the material and thickness of the light reflector48, for example. For example, the light reflecting member24is formed by the same method as the light reflector48, for example. The radiation detector RD1according to the modification example does not need to include the light reflecting member24. Even when the radiation detector RD1according to the modification example does not include the light reflecting member24, the plurality of portions1p,1q,1r, and1sare joined to each other.

In the present modification example, when viewed in the second direction D2, each of the plurality of photodetection regions23a,23b,23c, and23dof the semiconductor substrate11ahas an outline shape corresponding to an outline shape of the coupling surface3cof the corresponding portion1p,1q,1r, or1sof the plurality of portions1p,1q,1r, and1s, the coupling surface3copposing the semiconductor substrate11a. When viewed in the second direction D2, each of the plurality of photodetection regions23a,23b,23c, and23dof the semiconductor substrate11bhas an outline shape corresponding to an outline shape of the coupling surface3dof the corresponding portion1p,1q,1r, or1sof the plurality of portions1p,1q,1r, and1s, the coupling surface3dopposing the semiconductor substrate11b. In the present modification example, the coupling surfaces3cand3dof the portions1p,1q,1r, and1shave a rectangular shape when viewed in the second direction D2. The corresponding photodetection region23a,23b,23c, or23dhave a rectangular outline shape. For example, when the coupling surface3cconstitutes the first coupling surface, the coupling surface3econstitutes a second coupling surface.

FIG.12illustrates paths of scintillation lights incident on the coupling surface3c. The scintillation lights incident on the coupling surface3care generated in the portion1p. The scintillation lights generated in the portion1pare confined in the portion1p, for example. In the present modification example, for example, the light reflecting member24is disposed on the opposing surface3b. The radiation is incident from the opposing surface3aof the portion1p. The scintillation lights include, for example, a light L1and a light L2incident on the coupling surface3cfrom the scintillation light generation point GP1. The light L1is incident substantially perpendicularly on the coupling surface3c. A substantially perpendicular incidence angle of the light L1is smaller than a critical angle on the coupling surface3c. The light L1is incident on the coupling surface3cand is incident on the coupling surface3c. The light L1is detected in the photodetection region23aof the semiconductor photodetector10a. The light L2is incident on the coupling surface3cat an incidence angle EA1. When the incidence angle EA1of the light L2is smaller than the critical angle on the coupling surface3c, the light L2is incident on the coupling surface3cand is incident on the coupling surface3c. The light L2is detected in the photodetection region23aof the semiconductor photodetector10a. When the incidence angle EA1of the light L2is equal to or larger than the critical angle on the coupling surface3c, the light L2is totally reflected from the coupling surface3c, for example. In the present modification example, since the light reflecting member24is disposed, the light L2totally reflected from the coupling surface3ctends not to be incident on another portion of the scintillator1, for example, the portion1q. The scintillation lights generated in the portion1ptend not to be detected in the photodetection regions23b,23c, and23dother than the photodetection region23a.

The scintillation lights include, for example, a light L3and a light L4incident on the coupling surface3dfrom the scintillation light generation point GP1. The light L1is incident substantially perpendicularly on the coupling surface3d. A substantially perpendicular incidence angle of the light L3is smaller than a critical angle on the coupling surface3d. The light L3is incident on the coupling surface3dand is incident on the coupling surface3d. The light L3is detected in the photodetection region23aof the semiconductor photodetector10b. The light L4is incident on the coupling surface3dat an incidence angle EA2. When the incidence angle EA2of the light L4is smaller than the critical angle on the coupling surface3d, the light L4is incident on the coupling surface3dand is incident on the coupling surface3d. The light L4is detected in the photodetection region23aof the semiconductor photodetector10b. When the incidence angle EA2of the light L4is equal to or larger than the critical angle on the coupling surface3d, the light L4is totally reflected from the coupling surface3d, for example. In the present modification example, since the light reflecting member24is disposed, the light L4totally reflected from the coupling surface3dtends not to be incident on another portion of the scintillator1, for example, the portion1q. The scintillation lights generated in the portion1ptend not to be detected in the photodetection regions23b,23c, and23dother than the photodetection region23a. The photodetection region23adetects the scintillation lights generated in the portion1pand reflected from the light reflecting member24.

In the present modification example, the semiconductor photodetectors10aand10badhere to the scintillator1with adhesives having the same refractive index. Therefore, the critical angles on the coupling surfaces3cand3dare equal to each other. The refractive index of the scintillator1is, for example, 1.8. The refractive index of the adhesives is, for example, 1.5. The critical angles of the scintillation lights on the coupling surfaces3cand3dare, for example, about 56.4 degrees.FIG.12illustrates the paths of some scintillation lights when the scintillator1is viewed in the third direction D3. The semiconductor photodetector10adetects the light L2in a region R1in which the incidence angle EA1of the light L2on the side surface1cis smaller than the critical angle on the coupling surface3c. The region R1expands to, for example, the entire region of the coupling surface3c. The semiconductor photodetector10bdetects the light L4in a region R2in which the incidence angle EA2of the light L4on the coupling surface3dis smaller than the critical angle on the coupling surface3d. The region R2expands to, for example, the entire region of the coupling surface3d.

In the present modification example, the scintillation lights generated in the portions1q,1r, and1sare incident on the photodetection regions23b,23c, and23d, respectively, and are detected by the semiconductor photodetectors10aand10bdisposed on the coupling surfaces3c, respectively. The scintillation lights generated in the portions1q,1r, and1sare confined, for example, in the portions1q,1r, and1s, respectively. In the present modification example, for example, electrical signals output in response to the incidence of the scintillation lights on the photodetection regions23a,23b,23c, and23dare added by a signal processing circuit connected to the wiring members30aand30b.

As illustrated inFIGS.11and12, the radiation detector RD1includes a light reflector56for each of the portions1p,1q,1r, and1s, for example. In the portion1p, for example, the light reflector56is disposed on at least one of the opposing surfaces3aand3band the coupling surfaces3eand3f, for example. In the present modification example, the light reflectors56are disposed on the opposing surface3aand the coupling surfaces3eand3f. In the portions1qand1r, for example, the light reflector56is disposed on at least one of the coupling surfaces3eand3f, for example. In the present modification example, the light reflectors56are disposed on the coupling surfaces3eand3f. In the portion1s, for example, the light reflector56is disposed on at least one of the opposing surfaces3aand3band the coupling surfaces3eand3f, for example. In the present modification example, the light reflectors56are disposed on the opposing surface3band the coupling surfaces3eand3f. The light reflector56reflects the scintillation light so that the scintillation light incident on the opposing surface3aand the coupling surfaces3eand3fis not emitted outside the scintillator1.

A material and a thickness of the light reflector56according to the present modification example are, for example, the same as the material and thickness of the light reflector48. For example, the light reflector56according to the present modification example is formed by the same method as the light reflector48. The materials and the thicknesses of the light reflector56and the light reflecting member24according to the present modification example and the light reflector56and the light reflector48according to the first embodiment are the same as each other, for example. The light reflector56according to the first embodiment, the light reflector56according to the present modification example, the light reflecting member24, and the light reflector48are formed, for example, by the same method. The materials and the thicknesses of the light reflector56and the light reflecting member24according to the present modification example and the light reflector56and the light reflector48according to the first embodiment are different from each other, for example. The light reflector56according to the first embodiment, the light reflector56according to the present modification example, the light reflecting member24, and the light reflector48are formed, for example, by different methods from each other. The light reflectors56disposed at the portions1p,1q,1r, and1smay be integrally formed with the adjacent light reflectors56. The radiation detector RD1according to the present modification example does not need to include the light reflector56.

As described above, the radiation detector RD1includes: the scintillator1including a pair of end surfaces1aand1bopposing each other in the first direction D1, and the side surface1cand the side surface1dopposing each other in the second direction D2intersecting the first direction D1and coupling the pair of end surfaces1aand1b, the scintillator1having the rectangular shape when viewed in the first direction D1; the semiconductor photodetector10aincluding the semiconductor substrate11adisposed to oppose the side surface1c; the semiconductor photodetector10bincluding the semiconductor substrate11bdisposed to oppose the side surface1d; the wiring member30aelectrically connected to the semiconductor photodetector10a; and the wiring member30belectrically connected to the semiconductor photodetector10b. The length of the scintillator1in the first direction D1is longer than the length of the scintillator1in the second direction D2and the length of the scintillator1in the third direction D3parallel to the side surface1c. A length of the side surface1cin the first direction D1is longer than a width of the side surface1cin the third direction D3. A length of the side surface1din the first direction D1is longer than a width of the side surface1din the third direction D3. The semiconductor substrate11aincludes the portion21acovered with the side surface1c, and the portion22adisposed with the portion21ain the first direction D1and exposed from the side surface1c. The semiconductor substrate11bincludes the portion21bcovered with the side surface1d, and the portion22bdisposed with the portion21bin the first direction D1and exposed from the side surface1d. Each of the semiconductor photodetector10aand the semiconductor photodetector10bincludes the plurality of photodetection regions23a,23b,23c, and23dincluding at least one avalanche photodiode12arranged to operate in Geiger mode, and the at least one quenching resistor13electrically connected in series with one of the anode or the cathode of the corresponding avalanche photodiode12of the at least one avalanche photodiode12. The semiconductor photodetector10aincludes the plurality of electrodes17a,17b,17, and17delectrically connected to the at least one quenching resistor13included in the semiconductor photodetector10aand included in the corresponding photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23d, and the electrode18electrically connected to the other of the anode or the cathode of each of the avalanche photodiodes12included in the semiconductor photodetector10aand included in the corresponding photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23d. The semiconductor photodetector10bincludes the plurality of electrodes17a,17b,17, and17delectrically connected to the at least one quenching resistor13included in the semiconductor photodetector10band included in the corresponding photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23d, and the electrode18electrically connected to the other of the anode or the cathode of each of the avalanche photodiodes12included in the semiconductor photodetector10band included in the corresponding photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23d. The plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor photodetector10aare disposed in the portion21a. The plurality of electrodes17a,17b,17, and17dand the electrode18included in the semiconductor photodetector10aare disposed in the portion22a. The plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor photodetector10bare disposed in the portion21b. The plurality of electrodes17a,17b,17, and17dand the electrode18included in the semiconductor photodetector10bare disposed in the portion22b. The wiring member30aincludes a plurality of conductors31a,31b,31c, and31delectrically connected to the corresponding electrode17a,17b,17, or17dof the plurality of electrodes17a,17b,17, and17dincluded in the semiconductor photodetector10a, and a conductor32connected to the electrode18included in the semiconductor photodetector10a. The wiring member30bincludes a plurality of conductors31a,31b,31c, and31delectrically connected to the corresponding electrode17a,17b,17, or17dof the plurality of electrodes17a,17b,17, and17dincluded in the semiconductor photodetector10b, and a conductor32connected to the electrode18included in the semiconductor photodetector10b.

The radiation detector RD1includes the scintillator1elongated in the first direction D1and includes the semiconductor photodetector10adisposed on the side surface1cof the scintillator1. The radiation detector RD1includes the semiconductor photodetector10bdisposed on the side surface1dof the scintillator1. The semiconductor photodetector10adetects the scintillation light incident on the side surface1con which the semiconductor photodetector10ais disposed. The semiconductor photodetector10bdetects the scintillation light incident on the side surface1don which the semiconductor photodetector10bis disposed. The length of the scintillator1in the second direction D2is longer than the length of the scintillator1in the first direction D1. Therefore, a distance from the scintillation light generation point GP1to each of the side surface1cand the side surface Id is short. An arrival time of the scintillation light to each of the semiconductor photodetectors10aand10bis short, and the radiation detector RD1achieves high time resolution. The radiation detector RD1includes the semiconductor photodetector10aand the semiconductor photodetector10b. Therefore, the radiation detector RD1achieves high detection sensitivity as compared with a radiation detector including a single semiconductor photodetector disposed on one side surface of a scintillator.

The radiation detector RD1includes the semiconductor photodetectors10aand10bin which the plurality of photodetection regions23a,23b,23c, and23dare disposed in the first direction D1. For example, a distance between the scintillation light generation point GP1and the end surface1aof the scintillator1in the first direction D1is obtained from a position on the photodetection region23a,23b,23c, or23dwhere the most scintillation lights are detected, of the plurality of photodetection regions23a,23b,23c, and23d.

As a result, a magnitude of energy of radiation incident from the end surface1aof the scintillator1is accurately measured. Therefore, the radiation detector RD1achieves high detection sensitivity.

In the radiation detector RD1, when viewed in the second direction D2, one region formed by the outline of the plurality of photodetection regions23a,23b,23c, and23dof the semiconductor substrate11ahas an outline shape corresponding to the outline shape of the side surface1c. When viewed in the second direction D2, one region formed by the outline of the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11bhas an outline shape corresponding to an outline shape of the side surface1d.

In a configuration in which the one region formed by the outline of the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11ahas the shape corresponding to the outline shape of the side surface1c, the plurality of photodetection regions23a,23b,23c, and23dtend not to be disposed at positions on the semiconductor substrate11awhere no scintillation lights can be received. Therefore, increase in dark count and capacitance in the photodetection regions23a,23b,23c, and23dof the semiconductor substrate11ais curbed. In a configuration in which the one region formed by the outline of the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11bhas the shape corresponding to the outline shape of the side surface1d, the plurality of photodetection regions23a,23b,23c, and23dtend not to be disposed at positions on the semiconductor substrate11bwhere no scintillation lights can be received. Therefore, increase in dark count and capacitance in the photodetection regions23a,23b,23c, and23dof the semiconductor substrate11bis curbed. These configurations reduce detection errors of scintillation lights. As a result, the radiation detector RD1reliably improves the time resolution and the detection sensitivity of the semiconductor photodetector10aand the semiconductor photodetector10b.

In the radiation detector RD1, the scintillator1has the plurality of portions1p,1q,1r, and1sdisposed independently of each other in the first direction D1. Each of the plurality of portions1p,1q,1r, and1sis positioned corresponding to the corresponding photodetection region23a,23b,23c, or23dof the plurality of photodetection regions23a,23b,23c, and23ddisposed in each of the semiconductor substrate11aand the semiconductor substrate11b. Each of the plurality of portions1p,1q,1r, and1sincludes the pair of opposing surfaces3aand3bthat oppose each other in the first direction D1and the coupling surfaces3cand3dthat oppose the pair of opposing surfaces3aand3b. The coupling surface3coppose the semiconductor substrate11a. The coupling surface3doppose the semiconductor substrate11band oppose the coupling surface3cin the second direction D2.

In this configuration, the scintillation lights generated in the portions1p,1q,1r, and1sare confined in the portions1p,1q,1r, and1s, respectively. The photodetection regions23a,23b,23c, and23dcorresponding to the portion1p,1q,1r, or1sreliably detect scintillation lights generated in the corresponding portion1p,1q,1r, or1s. Therefore, the radiation detector RD1reliably achieves high detection sensitivity.

In the radiation detector RD1, the plurality of portions1p,1q,1r, and1sare joined to each other.

This configuration improves the physical strength of the scintillator1. Therefore, the radiation detector RD1more reliably achieves high detection sensitivity.

The radiation detector RD1includes the light reflecting members24. The light reflecting members24are disposed between the plurality of portions1p,1q,1r, and1s.

In this configuration, a scintillation light generated in each of the portions1p,1q,1r, and1sis reliably confined in the corresponding portion1p,1q,1r, or1s. The photodetection regions23a,23b,23c, and23dcorresponding to the portion1p,1q,1r, or1smore reliably detect scintillation lights generated in the portions1p,1q,1r, and1s.

Therefore, the electrical signal output in response to the incidence of the scintillation light for each of the photodetection regions23a,23b,23c, and23dis processed by the signal processing circuit connected to the wiring members30aand30b. Even when the portions1p,1q,1r, and1sare separated from each other and disposed in the first direction D1, the scintillation light generated in the portion1pis not incident on the portion1q, for example. In this case, the scintillation lights generated in the portion1pcorresponding to the photodetection region23aare detected individually in the photodetection region23a. When the scintillation lights generated in the portions1q,1r, and1sare confined in the portions1q,1r, and1s, respectively, the scintillation lights generated in the portions1q,1r, and1sare detected individually in the photodetection regions23b,23c, and23d, respectively. Therefore, the radiation detector RD1still more reliably achieves high detection sensitivity.

In the radiation detector RD1, when viewed in the second direction D2, each of the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11ahas an outline shape corresponding to an outline shape of the coupling surface3cof a corresponding portion1p,1q,1r, or1sof the plurality of portions1p,1q,1r, and1s, the coupling surface3copposing the semiconductor substrate11a. When viewed in the second direction D2, each of the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11bhas an outline shape corresponding to an outline shape of the coupling surface3dof the corresponding portion1p,1q,1r, or1sof the plurality of portions1p,1q,1r, and1s, the coupling surface3dthat opposes the semiconductor substrate11b.

In a configuration in which each of the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11ahas the outline shape corresponding to the outline shape of the coupling surface3cof the corresponding portion1p,1q,1r, or1sof the plurality of portions1p,1q,1r, and1s, the coupling surface3copposing the semiconductor substrate11a, the plurality of photodetection regions23a,23b,23c, and23dtend not to be disposed at positions on the semiconductor substrate11awhere no scintillation lights can be received. In a configuration in which each of the plurality of photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11bhas the outline shape corresponding to the outline shape of the coupling surface3dof the corresponding portion1p,1q,1r, or1sof the plurality of portions1p,1q,1r, and1s, the coupling surface3dthat opposes the semiconductor substrate11b, the plurality of photodetection regions23a,23b,23c, and23dtend not to be disposed at positions on the semiconductor substrate11bwhere no scintillation lights can be received. Therefore, this configuration curbs increase in dark count and capacitance in the plurality of photodetection regions. As a result, this configuration reliably improves the time resolution and the detection sensitivity of the radiation detector RD1.

In the radiation detector RD1, the plurality of photodetection regions23a,23b,23c, and23dinclude the photodetection regions and the photodetection region23dcloser to the portions22aand22dthan the photodetection region23a. The width of the conductive wire14aelectrically connecting the electrode17acorresponding to the photodetection region23aand the photodetection region23ais larger than the width of the conductive wire14delectrically connecting the electrode17dcorresponding to the photodetection region23dand the photodetection region23d.

In this configuration, an electrical resistance difference between the conductive wire14aelectrically connecting the electrode17acorresponding to the photodetection region23aand the photodetection region23aand the conductive wire14delectrically connecting the electrode17dcorresponding to the photodetection region23dand the photodetection region23dis reduced. The length of the conductive wire14aelectrically connecting the electrode17acorresponding to the photodetection region23aand the photodetection region23ais longer than the length of the conductive wire14delectrically connecting the electrode17dcorresponding to the photodetection region23dand the photodetection region23d. As the lengths of the conductive wires14aand14dincrease, the electrical resistance of the conductive wires14aand14dincreases. As the widths of the conductive wires14aand14dincrease, the electrical resistance of the conductive wires14aand14ddecreases. Therefore, in the configuration in which the width of the long conductive wire14ais larger than the width of the short conductive wire14d, an electrical resistance difference between the electrical resistance of the long conductive wire14aand the electrical resistance of the short conductive wire14dis reduced. Therefore, this configuration more reliably improves the time resolution of the radiation detector RD1.

The radiation detector RD1includes the reinforcement body45disposed between the portions22aand22b. The reinforcement body45covers the portion22aand the portion22b, and couples the portion22aand the portion22b.

In this configuration, the reinforcement body45disposed between the portions22aand22bimproves the mechanical strength of the portions22aand22b. The wiring members30aand30bpositioned in the portion22aand the portion22b, respectively, are protected with the reinforcement body45. The mechanical strength of the portions22aand22bis improved, and the surfaces11dand11fcan be polished, for example.

In the radiation detector RD1, the semiconductor substrate11aincludes the surface11copposing the scintillator1in the second direction D2and the surface11dopposing the surface11cin the second direction D2. The semiconductor substrate11bincludes the surface11eopposing the scintillator1in the second direction D2and the surface11fopposing the surface11ein the second direction D2. The surface11dand the surface11finclude polished surfaces.

In a configuration in which the surface11dincludes a polished surface, the semiconductor substrate11acan be thinned by polishing the surface11d. In a configuration in which the surface11fincludes a polished surface, the semiconductor substrate11bcan be thinned by polishing the surface11f. A size of the radiation detector RD1can be reduced in a thickness direction of the semiconductor substrate11a. A size of the radiation detector RD1can be reduced in a thickness direction of the semiconductor substrate11b.

The radiation detector RD1includes: the base40aincluding the surface40cand the surface40dopposing each other in the second direction D2and be disposed such that the semiconductor substrate11ais positioned between the surface40dand the scintillator1; the base40bincluding the surface40eand the surface40fopposing each other in the second direction D2and be disposed such that the semiconductor substrate11bis positioned between the surface40eand the scintillator1; the plurality of terminals41a,41b,41c, and41ddisposed on the surface40c; the terminal42disposed on the surface40c; the plurality of terminals41a,41b,41c, and41ddisposed on the surface40e; the terminal42disposed on the surface40e; the wire43electrically connecting each of the plurality of terminals41a,41b,41c, and41ddisposed on the surface40cand each of the electrodes17a,17b,17c, and17ddisposed in the portion22a; the wire44electrically connecting the terminal42disposed on the surface40cand the electrode18disposed in the portion22a; the wire43electrically connecting each of the plurality of terminals41a,41b,41c, and41ddisposed on the surface40eand each of the electrodes17a,17b,17c, and17ddisposed in the portion22b; and the wire44electrically connecting the terminal42disposed on the surface40eand the electrode18disposed in the portion22b. The base40aincludes the portion51acovered with the semiconductor substrate11a, and the portion52adisposed with the portion51ain the first direction D1and exposed from the semiconductor substrate11a. The base40bincludes the portion51bcovered with the semiconductor substrate11b, and the portion52bdisposed with the portion51bin the first direction D1and exposed from the semiconductor substrate11b. The terminals41a,41b,41c, and41dand the terminal42disposed on the surface40care positioned on the portion52a. The terminals41a,41b,41c, and41dand the terminal42disposed on the surface40eare positioned on the portion52b.

A configuration in which the bases40aand40bare provided improves the mechanical strength of the radiation detector RD1. Therefore, this configuration reliably realizes the radiation detector RD1having high mechanical strength.

The radiation detector RD1includes the cover body47adisposed such that the semiconductor substrate11ais positioned between the cover body47aand the scintillator1, and the cover body47bdisposed such that the semiconductor substrate11bis positioned between the cover body47band the scintillator1. Each of the cover body47aand the cover body47bincludes at least one of the light reflector48and the electrical insulator49.

For example, a configuration in which each of the cover body47aand the cover body47bincludes the light reflector48improves light reflection characteristics of the scintillation light. For example, a configuration in which each of the cover body47aand the cover body47bincludes the electrical insulator49improves electrical insulation between the radiation detectors RD1adjacent to each other.

In the radiation detector RD1, the wiring member30ais disposed on the same side as the scintillator1relative to the semiconductor substrate11a. The wiring member30bis disposed on the same side as the scintillator1relative to the semiconductor substrate11b.

In a configuration in which the wiring member30ais disposed on the same side as the scintillator1relative to the semiconductor substrate11a, there is no need to provide a substrate for connecting the wiring member30ato the electrodes17a,17b,17c, and17dand the electrode18included in the semiconductor photodetector10athrough die bonding, for example. In a configuration in which the wiring member30bis disposed on the same side as the scintillator1relative to the semiconductor substrate11b, there is no need to provide a substrate for connecting the wiring member30bto the electrodes17a,17b,17c, and17dand the electrode18included in the semiconductor photodetector10bthrough die bonding, for example. Therefore, this configuration more reliably simplifies the configuration of the radiation detector RD1.

In the radiation detector RD1, at least a part of the wiring member30aand the scintillator1are disposed in front of the same surface of the semiconductor substrate11a. That is, at least a part of the wiring member30band the scintillator1are disposed in front of the same surface of the semiconductor substrate11b, for example.

In the configuration in which at least a part of the wiring member30aand the scintillator1are disposed in front of the same surface of the semiconductor substrate11a, the space efficiency of the radiation detector RD1is improved as compared with a configuration in which at least a part of the wiring member30aand the scintillator1are disposed in front of corresponding different surfaces of the semiconductor substrates11a. In the configuration in which at least a part of the wiring member30band the scintillator1are disposed in front of the same surface of the semiconductor substrate11b, the space efficiency of the radiation detector RD1is improved as compared with a configuration in which at least a part of the wiring member30band the scintillator1are disposed in front of corresponding different surfaces of the semiconductor substrates11b.

In the radiation detector RD1, at least a part of the wiring member30aand the scintillator1are disposed in front of the same surface of the base40a. At least a part of the wiring member30band the scintillator1are disposed in front of the same surface of the base40b, for example.

In the configuration in which at least a part of the wiring member30aand the scintillator1are disposed in front of the same surface of the base40a, the wiring member30ais easily connected to the electrodes17a,17b,17c,17d, and18included in the semiconductor photodetector10athrough die bonding. In the configuration in which at least a part of the wiring member30band the scintillator1are disposed in front of the same surface of the base40b, the wiring member30bis easily connected to the electrodes17a,17b,17c,17d, and18included in the semiconductor photodetector10bthrough die bonding.

In the radiation detector RD1, the wiring member30aand the wiring member30band the semiconductor substrate11aand the semiconductor substrate11bhave flexibility. The flexibility of the wiring member30ais higher than the flexibility of the semiconductor substrate11a. The flexibility of the wiring member30bis higher than the flexibility of the semiconductor substrate11b.

In a configuration in which the flexibility of the wiring member30ais higher than the flexibility of the semiconductor substrate11a, vibration of the wiring member30atends not to be transmitted to the semiconductor substrate11a. The force from the wiring member30atends not to be applied to the semiconductor substrate11a, and the semiconductor substrate11atends not to be physically damaged. In a configuration in which the flexibility of the wiring member30bis higher than the flexibility of the semiconductor substrate11b, vibration of the wiring member30btends not to be transmitted to the semiconductor substrate11b. The force from the wiring member30btends not to be applied to the semiconductor substrate11b, and the semiconductor substrate11btends not to be physically damaged. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector RD1.

Second Embodiment

Configurations of radiation detector arrays RA1and RA2according to a second embodiment will be described with reference toFIGS.13and14.FIG.13is a perspective view illustrating the radiation detector array RA1according to the second embodiment.FIG.14is a perspective view illustrating the radiation detector array RA2according to the second embodiment.

As illustrated inFIG.13, the radiation detector array RA1has a configuration in which a plurality of radiation detectors RD1according to the first embodiment or the modification example are disposed one-dimensionally, for example. The plurality of radiation detectors RD1are disposed in the third direction D3, for example. In an example illustrated inFIG.13, three radiation detectors RD1are disposed in the third direction D3. Of the plurality of radiation detectors RD1, any two radiation detectors RD1adjacent to each other are disposed such that the side surfaces1eand1fof the scintillator1included in one radiation detector RD1and the side surfaces1eand1fof the scintillator1included in the other radiation detector RD1oppose each other. Therefore, any two radiation detectors RD1adjacent to each other in the third direction D3are disposed such that the side surface1eof the scintillator1included in one radiation detector RD1and the side surface1fof the scintillator1included in the other radiation detector RD1oppose each other. Any two radiation detectors RD1adjacent to each other in the third direction D3are disposed such that the side surface1fof the scintillator1included in one radiation detector RD1and the side surface1eof the scintillator1included in the other radiation detector RD1oppose each other.

The semiconductor photodetector10aincluded in the one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1are one-dimensionally disposed, for example. In the present embodiment, the semiconductor photodetector10aincluded in the one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1are disposed in the third direction D3, for example. The semiconductor photodetector10bincluded in the one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1are one-dimensionally disposed, for example. In the present embodiment, the semiconductor photodetector10bincluded in the one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1are disposed in the third direction D3, for example.

The semiconductor photodetector10aincluded in the one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1are one-dimensionally disposed, and are integrally formed to each other, for example. That is, the semiconductor photodetectors10aincluded in the plurality of radiation detectors RD1are integrally formed. The semiconductor photodetectors10aare disposed in the third direction D3, for example. The semiconductor photodetector10bincluded in the one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1are one-dimensionally disposed, and are integrally formed to each other, for example. That is, the semiconductor photodetectors10bincluded in the plurality of radiation detectors RD1are integrally formed. The semiconductor photodetectors10bare disposed, for example, in the third direction D3, for example. That is, the semiconductor photodetectors10aincluded in the plurality of radiation detectors RD1does not need to be integrally formed. That is, the semiconductor photodetectors10bincluded in the plurality of radiation detectors RD1does not need to be integrally formed.

Each of the radiation detectors RD1includes, for example, the cover bodies47aand47band the light reflector56. When each of the radiation detectors RD1includes the light reflector56, the side surface1eof the scintillator1included in the one radiation detector RD1and the side surface1fof the scintillator1included in the other radiation detector RD1oppose each other in the third direction D3such that the light reflector56is positioned between the side surface1eand the side surface1f. Therefore, for example, the light reflector56disposed on the side surface1eof the scintillator1included in one radiation detector RD1and the light reflector56disposed on the side surface1fof the scintillator1included in the other radiation detector RD1are disposed between the side surface1ein the one radiation detector RD1and the side surface1fin the other radiation detector RD1. In the present embodiment, for example, one light reflector56may be disposed between the side surface1eof the scintillator1included in one radiation detector RD1and the side surface1fof the scintillator1included in the other radiation detector RD1. In the configuration in which one light reflector56is disposed, for example, the light reflector56is disposed on the side surface1ein the one radiation detector RD1, and the light reflector56is not disposed on the side surface1fin the other radiation detector RD1. Each of the radiation detectors RD1does not need to include at least one of the cover bodies47aand47band the light reflector56.

As illustrated inFIG.14, the radiation detector array RA2has a configuration in which a plurality of radiation detectors RD1according to the first embodiment or the modification example are two-dimensionally disposed in the matrix, for example. Of the plurality of radiation detectors RD1, the plurality of radiation detectors RD1disposed in a row direction constitute, for example, the radiation detector array RA1illustrated inFIG.13. In the radiation detector array RA2, for example, the radiation detector arrays RA1are disposed in a column direction. In the present embodiment, the column direction is the second direction D2, and the row direction is the third direction D3. Of the plurality of radiation detectors RD1, any two radiation detectors RD1adjacent to each other in the column direction are disposed such that either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in one radiation detector RD1and either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction. Therefore, any two radiation detectors RD1adjacent to each other in the column direction are disposed such that, for example, the semiconductor photodetector10aincluded in the one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1oppose each other in the column direction. Any two radiation detectors RD1adjacent to each other in the column direction are disposed such that, for example, the semiconductor photodetector10aincluded in the one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction. Any two radiation detectors RD1adjacent to each other are disposed such that, for example, the semiconductor photodetector10bincluded in the one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1oppose each other in the column direction. Any two radiation detectors RD1adjacent to each other in the column direction are disposed such that, for example, the semiconductor photodetector10bincluded in the one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction.

When each of the radiation detectors RD1includes the cover bodies47aand47b, in any two radiation detectors RD1adjacent to each other in the column direction, for example, the semiconductor photodetector10aincluded in one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction such that the cover bodies47aand47bare positioned between the semiconductor photodetectors10aand10b. In any two radiation detectors RD1adjacent to each other in the column direction, for example, the semiconductor photodetector10bincluded in one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1oppose each other in the column direction such that the cover bodies47band47aare positioned between the semiconductor photodetectors10band10a. In the example illustrated inFIG.14, three radiation detectors RD1are disposed in the third direction D3, and three radiation detectors RD1are disposed in the second direction D2. The radiation detector array RA2includes, for example, a total of nine radiation detectors RD1. For example, the end surface1aof one radiation detector RD1is flush with the end surface1aof another radiation detector RD1adjacent thereto in the row direction or the column direction.

As described above, the radiation detector array RA1according to the present embodiment includes the plurality of radiation detectors RD1disposed one-dimensionally. Each of the plurality of radiation detectors RD1is the radiation detector RD1according to the first embodiment or the modification example. The scintillator1includes the pair of side surfaces1eand1fthat couples the pair of end surfaces1aand1band couples the side surface1cand the side surface1d. Of the plurality of radiation detectors RD1, any two radiation detectors RD1adjacent to each other are disposed such that the side surfaces1eand1fof the scintillator1included in one radiation detector RD1and the side surfaces1eand1fof the scintillator1included in the other radiation detector RD1oppose each other.

The radiation detector array RA1according to the present embodiment realizes the radiation detector array in which the radiation detectors RD1having high time resolution and high detection sensitivity are one-dimensionally disposed.

In the radiation detector array RA1, the semiconductor photodetectors10aincluded in the plurality of radiation detectors RD1are integrally formed. The semiconductor photodetectors10bincluded in the plurality of radiation detectors RD1are integrally formed.

A configuration in which the semiconductor photodetectors10aare integrally formed and the semiconductor photodetectors10bare integrally formed improves mechanical strength of the radiation detector array RA1in which the plurality of radiation detectors RD1are one-dimensionally disposed.

The radiation detector array RA2according to the present embodiment includes the plurality of radiation detectors RD1disposed two-dimensionally in the matrix. Of the plurality of radiation detectors RD1, the plurality of radiation detectors RD1disposed in the row direction constitute, for example, the radiation detector array RA1according to the present embodiment or the modification example. Of the plurality of radiation detectors RD1, any two radiation detectors RD1adjacent to each other in the column direction are disposed such that either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in one radiation detector RD1and either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction.

A configuration in which the plurality of radiation detectors RD1are two-dimensionally disposed in the matrix realizes the radiation detector array RA2in which the radiation detectors RD1having high time resolution and high detection sensitivity are two-dimensionally disposed in the matrix. In the present embodiment, when the radiation detectors RD1include the light reflector56, the scintillation light incident on the side surface1eof the scintillator1included in one radiation detector RD1tends not to be incident on the side surface1fof the scintillator1included in another radiation detector RD1, for example.

Third Embodiment

Configurations of radiation detector arrays RA1and RA2according to a third embodiment will be described with reference toFIGS.15and16.FIG.15is a perspective view illustrating the radiation detector array RA1according to the third embodiment.FIG.16is a perspective view illustrating the radiation detector array RA2according to the third embodiment.

As illustrated inFIG.15, the radiation detector array RA1has a configuration in which the plurality of radiation detectors RD1according to the first embodiment or the modification example are disposed one-dimensionally, for example. The plurality of radiation detectors RD1are disposed in the third direction D3, for example. In an example illustrated inFIG.15, three radiation detectors RD1of the first embodiment are disposed in the third direction D3. Of the plurality of radiation detectors RD1, any two radiation detectors RD1adjacent to each other are disposed such that the side surfaces1eand1fof the scintillator1included in one radiation detector RD1and either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other. Therefore, any two radiation detectors RD1adjacent to each other in the third direction D3are disposed such that the side surface1eof the scintillator1included in one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the third direction D3. Any two radiation detectors RD1adjacent to each other in the third direction D3are disposed such that the side surface1fof the scintillator1included in one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1oppose each other in the third direction D3.

Each of the radiation detectors RD1includes, for example, the cover bodies47aand47band the light reflector56. In this case, for example, in any two radiation detectors RD1adjacent to each other in the third direction D3, the side surface1eof the scintillator1included in one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the third direction D3such that the cover body47band the light reflector56are positioned between the side surface1eand the semiconductor photodetector10b. For example, in any two radiation detectors RD1adjacent to each other in the third direction D3, the side surface1fof the scintillator1included in one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1oppose each other in the third direction D3such that the cover body47aand the light reflector56are positioned between the side surface1fand the semiconductor photodetector10a. Each of the radiation detectors RD1does not need to include at least one of the cover bodies47aand47band the light reflector56.

As illustrated inFIG.16, the radiation detector array RA2has a configuration in which the plurality of radiation detectors RD1according to the first embodiment or the modification example are two-dimensionally disposed in the matrix, for example. Of the plurality of radiation detectors RD1, the plurality of radiation detectors RD1disposed in the row direction all constitute, for example, the radiation detector array RA1illustrated inFIG.15. Therefore, in the radiation detector array RA2, the radiation detector arrays RA1are disposed in the column direction. In the present embodiment, the column direction is the second direction D2, and the row direction is the third direction D3. Of the plurality of radiation detectors RD1, any two radiation detectors RD1adjacent to each other in the column direction are disposed such that the side surfaces1eand1fof the scintillator1included in one radiation detector RD1and either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction. An opposing direction of the side surfaces1eand1fof the scintillator1included in the one radiation detector RD1and an opposing direction of the side surfaces1eand1fof the scintillator1included in the other radiation detector RD1intersect each other, for example. Therefore, any two radiation detectors RD1adjacent to each other in the column direction are disposed such that, for example, the side surface1eof the scintillator1included in one radiation detector RD1and the semiconductor photodetector10aincluded in the other radiation detector RD1oppose each other in the column direction. Any two radiation detectors RD1adjacent to each other in the column direction are disposed such that, for example, the side surface1fof the scintillator1included in one radiation detector RD1and the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction.

In the example illustrated inFIG.16, three radiation detectors RD1are disposed in the third direction D3, and three radiation detectors RD1are disposed in the second direction D2. The radiation detector array RA2includes, for example, a total of nine radiation detectors RD1. For example, the end surface1aof one radiation detector RD1is flush with the end surface1aof another radiation detector RD1adjacent thereto in the row direction or the column direction.

In the configuration in which each of the radiation detectors RD1includes the cover bodies47aand47band the light reflector56, for example, the side surface1eof the scintillator1included in one radiation detector RD1and the semiconductor photodetector10aincluded in another radiation detector RD1oppose each other in the column direction such that the cover body47aand the light reflector56are positioned between the side surface1eand the semiconductor photodetector10a. For example, the side surface1fof the scintillator1included in one radiation detector RD1and the semiconductor photodetector10bincluded in another radiation detector RD1oppose each other in the column direction such that the cover body47band the light reflector56are positioned between the side surface1fand the semiconductor photodetector10b.

As described above, the radiation detector array RA1according to the present embodiment includes the plurality of radiation detectors RD1disposed one-dimensionally. Each of the plurality of radiation detectors RD1is the radiation detector RD1according to the first embodiment or the modification example. The scintillator1includes the pair of side surfaces1eand1fthat couples the pair of end surfaces1aand1band couples the side surface1cand the side surface1d. Of the plurality of radiation detectors RD1, any two radiation detectors RD1adjacent to each other are disposed such that the side surfaces1eand1fof the scintillator1included in one radiation detector RD1and either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other.

The radiation detector array RA1according to the present embodiment realizes the radiation detector array in which the radiation detectors RD1having high time resolution and high detection sensitivity are one-dimensionally disposed.

The radiation detector array RA2according to the present embodiment includes the plurality of radiation detectors RD1disposed two-dimensionally in the matrix. Of the plurality of radiation detectors RD1, the plurality of radiation detectors RD1disposed in the row direction constitute, for example, the radiation detector array RA1according to the present embodiment. Of the plurality of radiation detectors RD1, any two radiation detectors RD1adjacent to each other in the column direction are disposed such that the side surfaces1eand1fof the scintillator1included in one radiation detector RD1and either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction.

The configuration in which the plurality of radiation detectors RD1are two-dimensionally disposed in the matrix realizes the radiation detector array RA2in which the radiation detectors RD1having high time resolution and high detection sensitivity are two-dimensionally disposed in the matrix. In a configuration in which the side surfaces1eand1fand either the semiconductor photodetector10aor the semiconductor photodetector10bincluded in the other radiation detector RD1oppose each other in the column direction, the plurality of radiation detectors RD1are two-dimensionally disposed in a smaller space as compared with a configuration in which the semiconductor photodetector10aand the semiconductor photodetector10boppose each other.

In the present embodiment, for example, the scintillation light incident on the side surface1eof the scintillator1included in one radiation detector RD1tends not to be incident on the scintillator1included in another radiation detector RD1, compared with a configuration in which the side surface1eof the scintillator1included in the one radiation detector RD1and the side surface1fof the scintillator1included in the other radiation detector RD1oppose each other. In the present embodiment, for example, the scintillation light incident on the side surface1fof the scintillator1included in one radiation detector RD1tends not to be incident on the scintillator1included in another radiation detector RD1, compared with a configuration in which the side surface1fof the scintillator1included in the one radiation detector RD1and the side surface1eof the scintillator1included in the other radiation detector RD1oppose each other.

An example of a method for producing the radiation detector RD1will be described with reference toFIG.17. Serial orders of steps of the producing method may be interchanged with each other. In an example of the producing method, first, the scintillator1and the semiconductor photodetectors10aand10bare prepared (S101).

Subsequently, the wiring members30aand30bare prepared and connected to the semiconductor photodetectors10aand10b(S102). For example, the wiring member30ais connected to the semiconductor photodetector10a, and the wiring member30bis connected to the semiconductor photodetector10b. The wiring members30aand30beach include a conductor31and a conductor32. The conductor31included in the wiring member30ais electrically connected to the electrodes17a,17b,17c, and17dof the semiconductor photodetector10a. The conductor31of the wiring member30bis electrically connected to the electrodes17a,17b,17c, and17dincluded in the semiconductor photodetector10b. The conductor32included in the wiring member30ais electrically connected to the electrode18included in the semiconductor photodetector10a. The conductor32included in the wiring member30bis electrically connected to the electrode18included in the semiconductor photodetector10b. The conductors31a,31b,31c, and31dincluded in the wiring member30aare electrically connected to the electrodes17a,17b,17c, and17d, respectively, included in the semiconductor photodetector10avia the corresponding conductive bump33, for example. The conductors31a,31b,31c, and31dincluded in the wiring member30bare electrically connected to the electrodes17a,17b,17c, and17d, respectively, included in the semiconductor photodetector10bvia the corresponding conductive bump33, for example. The conductor32included in the wiring member30ais connected to the electrode18included in the wiring member30avia the conductive bump33, for example. The conductor32included in the wiring member30bis connected to the electrode18included in the wiring member30bvia the conductive bump33, for example.

Subsequently, the scintillator1and the semiconductor photodetectors10aand10bare integral to each other (S103). This integration is achieved, for example, with an adhesive. The semiconductor photodetector10ais disposed, for example, on the side surface1cof the scintillator1. The semiconductor photodetector10bis disposed, for example, on the side surface Id of the scintillator1. Subsequently, the reinforcement body45is disposed between the portions22aand22b.

Subsequently, the semiconductor photodetectors10aand10bare thinned (S104). An element is thinned by, for example, polishing the surfaces11dand11f. The polishing of the surfaces11dand11fis performed by, for example, mechanical polishing or chemical polishing. The semiconductor photodetectors10aand10bare thinned in, for example, the radiation detector array RA1in which the plurality of radiation detectors RD1are disposed one-dimensionally. That is, the semiconductor photodetectors10aand10bincluded in the radiation detector array RA1are thinned. The plurality of thinned radiation detector arrays RA1are, for example, are individually divided to produce individual radiation detectors RD1. The individual dividing is performed by, for example, dicing. The plurality of thinned radiation detector arrays RA1may be disposed, for example, to be disposed in the column direction without being individually divided. The radiation detector array RA2in which the plurality of radiation detector arrays RA1are two-dimensionally disposed in the matrix may be produced.

The present embodiment includes a method for producing a radiation detector. The method for producing the radiation detector is as follows.

A method for producing a radiation detector including:preparing a scintillator;preparing a semiconductor photodetector;integrating the scintillator and the semiconductor photodetector; andthinning the semiconductor photodetector integrated with the scintillator, in whicha scintillator to be prepared includes a pair of end surfaces opposing each other in a first direction and one side surface coupling the pair of end surfaces, has a length in the first direction which is longer than a length in a second direction orthogonal to the one side surface, the one side surface having a length in the first direction which is longer than a width of the one side surface in a third direction orthogonal to the first direction and the second direction,the semiconductor photodetector to be prepared includes one semiconductor substrate including a first main surface and a second main surface opposing to each other, and the one semiconductor substrate includes a first portion in which photodetection regions are disposed, and a second portion disposed with the first portion in a direction orthogonal to a direction in which the first main surface and the second main surface oppose each other,each of the photodetection regions includes a plurality of avalanche photodiodes arranged to operate in Geiger mode and a plurality of quenching resistors electrically connected in series with one of an anode or a cathode of a corresponding avalanche photodiode of the plurality of avalanche photodiodes,the integrating of the scintillator and the semiconductor photodetector includes integrating the scintillator and the semiconductor photodetector such that the one side surface and the first main surface oppose each other and the first portion is covered with the one side surface and the second portion is exposed from the scintillator, and applying a resin such that the scintillator and the second portion are in contact with each other, andthe thinning of the semiconductor photodetector includes thinning the one semiconductor substrate from the second main surface side.

The method for producing a radiation detector according to Producing Method 1, further including:preparing a wiring member; andelectrically connecting the wiring member to the semiconductor photodetector, in whichthe semiconductor photodetector to be prepared further includes a first electrode and a second electrode disposed in the second portion, the first electrode is connected in parallel with the plurality of quenching resistors, and the second electrode is connected in parallel with the other of the anode or the cathode of each of the plurality of avalanche photodiodes,the wiring member to be prepared includes a first conductor and a second conductor,the electrical connecting of the wiring member includes connecting the first conductor to the first electrode and connecting the second conductor to the second electrode, andthe applying of the resin includes applying the resin to be in contact with a portion position on the second portion, the portion being included in the wiring member electrically connected to the semiconductor photodetector.

The method for producing a radiation detector according to Producing Method 1, in whichthe scintillator to be prepared further includes another side surface opposing the one side surface,the semiconductor photodetector to be prepared includes a first semiconductor photodetector and a second semiconductor photodetector, the first semiconductor photodetector includes the one semiconductor substrate including the first portion and the second portion, the second semiconductor photodetector includes another semiconductor substrate including a first main surface and a second main surface opposing each other, and the other semiconductor substrate includes a third portion in which the photodetection regions are disposed, and a fourth portion disposed with the third portion in the direction orthogonal to a direction in which the first main surface and the second main surface oppose each other,integrating the scintillator and the semiconductor photodetector includesintegrating the scintillator and the first semiconductor photodetector such that the one side surface and the first main surface oppose each other, the first portion is covered with the one side surface, and the second portion is exposed from the scintillator,integrating the scintillator and the second semiconductor photodetector such that the other side surface and the first main surface oppose each other, the third portion is covered with the other side surface, and the fourth portion is exposed from the scintillator, andapplying the resin to be in contact with the scintillator and the second portion of the one semiconductor substrate included in the first semiconductor photodetector, and to be in contact with the scintillator and the fourth portion of the other semiconductor substrate included in the second semiconductor photodetector, andthe thinning of the semiconductor photodetector includes thinning the one semiconductor substrate included in the first semiconductor photodetector from the second main surface side, and thinning the other semiconductor substrate included in the second semiconductor photodetector from the second main surface side.

The method for producing a radiation detector according to Producing Method 3, further including:preparing a wiring member; andelectrically connecting the wiring member to the semiconductor photodetector, in whichthe first semiconductor photodetector further includes a first electrode and a second electrode disposed in the second portion, and the second semiconductor photodetector further includes a third electrode and a fourth electrode disposed in the fourth portion,the first electrode is connected in parallel with the plurality of quenching resistors, and the second electrode is connected in parallel with the other of the anode or the cathode of each of the plurality of avalanche photodiodes,the third electrode is connected in parallel with the plurality of quenching resistors, and the fourth electrode is connected in parallel with the other of the anode or the cathode of each of the plurality of avalanche photodiodes,the wiring member to be prepared includes a first wiring member and a second wiring member including a first conductor and a second conductor, respectively,the electrical connecting of the wiring member includes connecting the first conductor of the first wiring member to the first electrode, connecting the second conductor of the first wiring member to the second electrode, connecting the first conductor of the second wiring member to the third electrode, and connecting the second conductor of the second wiring member to the fourth electrode, andthe applying of the resin includes applying the resin to be in contact with a portion of the first wiring member electrically connected to the first semiconductor photodetector, the portion being positioned on the second portion, and a portion of the second wiring member electrically connected to the second semiconductor photodetector, the portion being positioned on the fourth portion.

The embodiments and the modification example of the present invention have been described above; however, the present invention is not absolutely limited to the above-described embodiments and can be variously modified without departing from the gist of the present invention.

In the radiation detector RD1, when viewed in the second direction D2, the photodetection regions23a,23b,23c, and23ddo not need to have the outline shapes corresponding to the outline shape of the side surface1cor1d. In the configuration in which the photodetection regions23a,23b,23c, and23dhave the outline shape corresponding to the outline shape of the side surface1cor1d, as described above, the photodetection regions23a,23b,23c, and23dtend not to be disposed at positions of the semiconductor substrate11aor11bwhere no scintillation lights can be received. Therefore, increase in dark count and capacitance in the photodetection regions23a,23b,23c, and23dincluded in the semiconductor substrate11aor11bis curbed. Therefore, this configuration more reliably improves the time resolution of the radiation detector RD1.

The radiation detector RD1does not need to include the light reflecting member24. In the configuration in which the radiation detector RD1includes the light reflecting member24, as described above, the scintillation light generated in each of the portions1p,1q,1r, and1sis reliably confined in the corresponding portion1p,1q,1r, or1s. The photodetection regions23a,23b,23c, and23dcorresponding to the portions1p,1q,1r, and1smore reliably detect scintillation lights generated in the portions1p,1q,1r, and1s. Therefore, the radiation detector RD1still more reliably achieves high time resolution.

The width of the conductive wire14aelectrically connecting the electrode17acorresponding to the photodetection region23aand the photodetection region23amay be larger than the width of the conductive wire14delectrically connecting the electrode17dcorresponding to the photodetection region23dand the photodetection region23d. In the configuration in which the width of the conductive wire14aelectrically connecting the electrode17acorresponding to the photodetection region23aand the photodetection region23ais larger than the width of the conductive wire14delectrically connecting the electrode17dcorresponding to the photodetection region23dand the photodetection region23d, as described above, the electrical resistance difference between the conductive wire14aelectrically connecting the electrode17acorresponding to the photodetection region23aand the photodetection region23aand the conductive wire14delectrically connecting the electrode17dcorresponding to the photodetection region23dand the photodetection region23dis reduced.

The radiation detector RD1does not need to include the base40a. The configuration in which the radiation detector RD1includes the base40aimproves the mechanical strength of the semiconductor substrate11aas described above. The radiation detector RD1does not need to include the base40b. The configuration in which the radiation detector RD1includes the base40bimproves the mechanical strength of the semiconductor substrate11bas described above. Therefore, this configuration reliably realizes the radiation detector RD1having high mechanical strength.

The radiation detector RD1does not need to include the reinforcement body45. In the configuration in which the radiation detector RD1includes the reinforcement body45, as described above, the reinforcement body45disposed between the portion22aand the portion22bimproves the mechanical strength of the portion22aand the portion22b. The reinforcement body45protects the wiring member30apositioned in the portion22aand the wiring member30bpositioned in the portion22b.

The radiation detector RD1does not need to include the cover bodies47aand47b. When the radiation detector RD1includes the cover bodies47aand47b, for example, the configuration in which each of the cover body47aand the cover body47bincludes the light reflector48improves the light reflection characteristics of the scintillation light. For example, a configuration in which each of the cover body47aand the cover body47bincludes the electrical insulator49improves electrical insulation between the radiation detectors RD1.

The wiring member30adoes not need to be disposed on the same side as the scintillator1relative to the semiconductor substrate11a. In a configuration in which the wiring member30ais disposed on the same side as the scintillator1relative to the semiconductor substrate11a, there is no need to provide a substrate for connecting the wiring member30ato the electrodes17and18included in the semiconductor photodetector10athrough die bonding, for example. The wiring member30bdoes not need to be disposed on the same side as the scintillator1relative to the semiconductor substrate11b. In a configuration in which the wiring member30bis disposed on the same side as the scintillator1relative to the semiconductor substrate11b, there is no need to provide a substrate for connecting the wiring member30band the electrodes17and18included in the semiconductor photodetector10bthrough die bonding, for example. Therefore, this configuration more reliably simplifies the configuration of the radiation detector RD1.

The flexibility of the wiring member30adoes not need to be higher than the flexibility of the semiconductor substrate11a. In a configuration in which the flexibility of the wiring member30ais higher than the flexibility of the semiconductor substrate11a, vibration of the wiring member30atends not to be transmitted to the semiconductor substrate11a. The flexibility of the wiring member30bdoes not need to be higher than the flexibility of the semiconductor substrate11b. In a configuration in which the flexibility of the wiring member30bis higher than the flexibility of the semiconductor substrate11b, as described above, vibration of the wiring member30btends not to be transmitted to the semiconductor substrate11b. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector RD1.

In the embodiments and the modification example, the example in which the semiconductor photodetectors are disposed on the two side surfaces1cand1dof the scintillator1, respectively, has been described, but the semiconductor photodetectors may be disposed on the four side surfaces1c,1d,1e, and1fof the scintillator1, respectively.

REFERENCE SIGNS LIST