Radiation detector, photodetector, and method for manufacturing radiation detector

Abstract

This radiation detector comprises an optical semiconductor element, support members that are positioned on one side of the optical semiconductor element in a first direction and are disposed in positions on both sides, in a second direction, of a region that overlaps a light receiving region when viewed from the first direction, a scintillator unit that is supported by the support members so as to face the optical semiconductor element in the first direction across the region, and a bonding member that is disposed in the region and is in contact with each of the optical semiconductor element, the support members, and the scintillator unit in the region, wherein the refractive index of a scintillator of the scintillator unit is 1.80 to 2.35 inclusive, and the refractive index of the bonding member is 1.60 to 2.00 inclusive.

Description

Radiation detector, photodetector, and method of manufacturing a radiation detector

[0001] The present disclosure relates to radiation detectors, photodetectors, and methods of manufacturing radiation detectors.

[0002] Patent Document 1 describes a radiation detector that includes a plurality of phosphor elements that emit light when exposed to radiation, and a plurality of photoelectric conversion elements that are adhered to the phosphor elements with an adhesive and detect the light emitted from the phosphor elements.

[0003] JP 2009-118943 A

[0004] In the radiation detector described in Patent Document 1, if the difference in refractive index between the phosphor element and the adhesive is large, there is a risk that the amount of light emitted from the phosphor element that is reflected at the interface between the phosphor element and the adhesive will increase. In this case, the amount of light incident on the photoelectric conversion element will decrease, which may result in a decrease in radiation detection efficiency. Furthermore, in the radiation detector described in Patent Document 1, there is a risk that the thickness of the adhesive disposed between the phosphor element and the photoelectric conversion element will vary. In this case, there will be a risk that the amount of light incident on the photoelectric conversion element will vary, which may result in a decrease in radiation detection efficiency.

[0005] An object of the present disclosure is to provide a radiation detector, a photodetector, and a method for manufacturing a radiation detector that can stably improve radiation detection efficiency.

[0006] A radiation detector according to one aspect of the present disclosure includes: [1] "an optical semiconductor element including a semiconductor layer constituting a light receiving region; support members disposed on both sides of a region located on one side of the optical semiconductor element in a first direction parallel to a thickness direction of the semiconductor layer and overlapping with the light receiving region when viewed from the first direction, in a second direction perpendicular to the first direction; and a scintillator unit supported by the support members so as to face the optical semiconductor element across the region in the first direction, wherein the optical semiconductor element, the support members, and the scintillator unit are disposed in the region, a bonding member in contact with each of the scintillator unit and the scintillator member, wherein the scintillator unit has a scintillator corresponding to the light-receiving region, the light-receiving region has a plurality of light-receiving sections connected in parallel with each other, each of the plurality of light-receiving sections includes an avalanche photodiode operating in Geiger mode and a quenching element connected in series with the avalanche photodiode, wherein the refractive index of the scintillator is 1.80 or more and 2.35 or less, and the refractive index of the bonding member is 1.60 or more and 2.00 or less.

[0007] In the radiation detector, a bonding member is disposed in a region located on one side of the optical semiconductor element in a first direction parallel to the thickness direction of the semiconductor layer and overlapping with the light receiving region when viewed from the first direction, and the bonding member is in contact with both the optical semiconductor element and the scintillator unit in the region. In this state, the refractive index of the scintillator is 1.80 or more and 2.35 or less, and the refractive index of the bonding member is 1.60 or more and 2.00 or less. This prevents light emitted from the scintillator from being reflected at the interface between the scintillator and the bonding member, thereby preventing a decrease in radiation detection efficiency. In addition, in the radiation detector, support members supporting the scintillator unit are disposed on both sides of the region located on one side of the optical semiconductor element in the first direction parallel to the thickness direction of the semiconductor layer and overlapping with the light receiving region when viewed from the first direction, in a second direction perpendicular to the first direction, and the bonding member is in contact with the support members in the region. This makes it possible to suppress variations in the thickness of the bonding member between the light-receiving region and the scintillator, and as a result, to suppress variations in the radiation detection efficiency. As a result, the radiation detector can achieve a stable improvement in the radiation detection efficiency.

[0008] A radiation detector according to one aspect of the present disclosure may be [2] "the radiation detector according to the above [1], wherein the optical semiconductor element further includes a first insulating layer disposed on the semiconductor layer on the region side, and the refractive index of the first insulating layer is higher than the refractive index of the bonding member and lower than the refractive index of the semiconductor layer." With this radiation detector, it is possible to suppress reflection of light emitted from the scintillator at the interface between the bonding member and the first insulating layer and at the interface between the first insulating layer and the semiconductor layer, thereby further improving the radiation detection efficiency.

[0009] A radiation detector according to one aspect of the present disclosure may be [3] "the radiation detector according to the above [2], wherein the optical semiconductor element further includes a second insulating layer disposed on the first insulating layer on the region side, the second insulating layer covering the quenching element, the second insulating layer having a plurality of first openings opening on both sides in the first direction, each of the plurality of first openings overlapping with a plurality of first light receiving units disposed in the effective region among the plurality of light receiving units when viewed from the first direction, a portion of the bonding member being disposed in each of the plurality of first openings, the portion of the bonding member being in contact with the first insulating layer." According to this radiation detector, light emitted from the scintillator enters the first insulating layer through the first openings provided in the second insulating layer for protecting the quenching element, thereby making it possible to suppress reflection of the light emitted from the scintillator at the interface between the bonding member and the second insulating layer and further improve radiation detection efficiency.

[0010] A radiation detector according to one aspect of the present disclosure may be [4] "the radiation detector according to the above [3], wherein the support member is disposed between the second insulating layer and the scintillator unit, the second insulating layer further has a plurality of second openings that open on both sides in the first direction, and a portion of the support member is disposed in each of the plurality of second openings." With this radiation detector, the distance between the light-receiving region and the scintillator and the thickness of the bonding member between the light-receiving region and the scintillator can be maintained accurately and stably.

[0011] A radiation detector according to one aspect of the present disclosure may be [5] "the radiation detector according to the above [4], wherein, when viewed from the first direction, each of the plurality of second openings overlaps with each of the plurality of second light receiving sections that are arranged outside the effective area among the plurality of light receiving sections." With this radiation detector, the distance between the light receiving section and the scintillator and the thickness of the bonding member between the light receiving section and the scintillator can be maintained accurately and stably. Furthermore, because each of the plurality of second openings overlaps with each of the plurality of second light receiving sections, the size of the radiation detector when viewed from the first direction can be reduced even when a plurality of second light receiving sections are provided.

[0012] A radiation detector according to one aspect of the present disclosure may be [6] "the radiation detector according to the above [5], in which the plurality of second light receiving sections are arranged in an outer edge region surrounding the effective region when viewed from the first direction." With this radiation detector, it is possible to suppress a decrease in the aperture ratio of the light receiving region.

[0013] A radiation detector according to one aspect of the present disclosure may be [7] "the radiation detector according to any one of the above [1] to [6], further including: a wiring board on which at least a plurality of photodetectors aligned in the second direction are mounted; a plurality of wires; and a protective member, wherein each of the plurality of photodetectors includes the optical semiconductor element, the support member disposed between the optical semiconductor element and the scintillator unit, and the bonding member, wherein each of the plurality of wires connects the optical semiconductor element to the wiring board on an outer side of the support member in the second direction, and the protective member covers the plurality of wires on an outer side of the support member in the second direction." With this radiation detector, in each of the plurality of photodetectors, the distance between the light-receiving region and the scintillator and the thickness of the bonding member between the light-receiving region and the scintillator can be accurately and stably maintained.

[0014] A radiation detector according to one aspect of the present disclosure may be [8] "the radiation detector according to any one of [1] to [6] above, further including: a wiring board on which the optical semiconductor element is mounted; and a wire connecting the optical semiconductor element and the wiring board, wherein the optical semiconductor element has a third opening that opens on both sides in the first direction, the wire passes through the third opening, and the third opening overlaps with the bonding member when viewed from the first direction." According to this radiation detector, for example, by arranging a part of the bonding member within the third opening of the optical semiconductor element, it is possible to protect the wire and accurately and stably maintain the thickness of the bonding member between the light-receiving region and the scintillator.

[0015] A radiation detector according to one aspect of the present disclosure may be [9] "the radiation detector according to any one of the above [1] to [8], in which the absolute value of the difference between the refractive index of the scintillator and the refractive index of the bonding member is 0.2 or less." According to this radiation detector, the difference in refractive index between the bonding member and the scintillator is smaller, and therefore it is possible to further suppress reflection of light emitted from the scintillator at the interface between the scintillator and the bonding member.

[0016] A radiation detector according to one aspect of the present disclosure may be

[10] "the radiation detector according to any one of the above [1] to [9], wherein the semiconductor layer has a surface facing the scintillator unit via the region in the first direction, the support member has a support surface supporting the scintillator unit, and the height from the surface to the support surface in the first direction is 200 μm or less." With this radiation detector, the thickness of the bonding member between the light-receiving region and the scintillator can be maintained at 200 μm or less, and absorption of light emitted from the scintillator by the bonding member can be suppressed.

[0017] A photodetector according to one aspect of the present disclosure is

[11] "a photodetector comprising: an optical semiconductor element including a semiconductor layer constituting a light-receiving region; and support members located on both sides in a second direction perpendicular to a first direction of a region that is located on one side of the optical semiconductor element in a first direction parallel to the thickness direction of the semiconductor layer and overlaps with the light-receiving region when viewed from the first direction, wherein the light-receiving region has a plurality of light-receiving units connected in parallel with each other, and each of the plurality of light-receiving units includes an avalanche photodiode operating in Geiger mode and a quenching element connected in series with the avalanche photodiode."

[0018] According to the above-described photodetector, for example, by placing the scintillator unit on a support member so that the scintillator faces the light-receiving region, and by placing a joining member between the light-receiving region and the scintillator, a radiation detector can be obtained that can maintain the distance between the light-receiving region and the scintillator and the thickness of the joining member between the light-receiving region and the scintillator.

[0019] A method for manufacturing a radiation detector according to one aspect of the present disclosure includes the steps of:

[12] "preparing an optical semiconductor element including a semiconductor layer constituting a light receiving region, a scintillator unit, and a bonding material; arranging support members on both sides, in a second direction perpendicular to the first direction, of a region that is located on one side of the optical semiconductor element in a first direction parallel to a thickness direction of the semiconductor layer and that overlaps with the light receiving region when viewed from the first direction; arranging the scintillator unit on the support member so as to face the optical semiconductor element across the region in the first direction; and arranging support members on the scintillator unit so as to be in contact with the optical semiconductor element, the support member, and the scintillator unit, respectively. and introducing the bonding material into the region as described above to form a bonding member, and bonding the optical semiconductor element and the scintillator unit with the bonding member, wherein the scintillator unit has a scintillator corresponding to the light-receiving region, the light-receiving region has a plurality of light-receiving sections connected in parallel with each other, each of the plurality of light-receiving sections including an avalanche photodiode operating in Geiger mode and a quenching element connected in series with the avalanche photodiode, wherein the refractive index of the scintillator is 1.80 or more and 2.35 or less, and the refractive index of the bonding member is 1.60 or more and 2.00 or less.

[0020] According to the method for manufacturing the radiation detector, for the same reasons as those for the radiation detector described above, it is possible to obtain a radiation detector that can stably improve the radiation detection efficiency.

[0021] A method for manufacturing a radiation detector according to one aspect of the present disclosure may be

[13] "the method for manufacturing a radiation detector according to the above

[12] , wherein in the step of arranging the support member, a resist is applied onto the optical semiconductor element, and a portion of the resist located in the region is removed to form the support member." According to this method for manufacturing a radiation detector, the support member can be formed with high precision.

[0022] A method for manufacturing a radiation detector according to one aspect of the present disclosure may be

[14] "the method for manufacturing a radiation detector according to the above

[12] , wherein in the step of arranging the support member, a mold is arranged on the optical semiconductor element, a resin material is introduced into the mold, and the resin material is cured to form the support member." According to this method for manufacturing a radiation detector, the support member can be easily formed.

[0023] A method for manufacturing a radiation detector according to one aspect of the present disclosure may be

[15] "the method for manufacturing a radiation detector according to the above

[14] , further comprising the steps of preparing a wiring board, mounting the optical semiconductor element on the wiring board, and connecting the optical semiconductor element and the wiring board with wires, wherein in the step of forming the support member, the resin material is introduced inside the mold so that the resin material covers the wires." According to this method for manufacturing a radiation detector, a support member having both the function of supporting a scintillator unit and the function of protecting the wires can be easily formed.

[0024] A method for manufacturing a radiation detector according to one aspect of the present disclosure may be

[16] "the method for manufacturing a radiation detector according to the above

[12] , further comprising the steps of preparing a wiring board and mounting the optical semiconductor element on the wiring board, wherein in the step of arranging the support members, the support members are attached to the wiring board at positions on both sides of the optical semiconductor element in the second direction." According to this method for manufacturing a radiation detector, the position of the support member can be adjusted depending on the mounting state of the optical semiconductor element on the wiring board.

[0025] The method for manufacturing a radiation detector according to one aspect of the present disclosure may be

[17] "the method for manufacturing a radiation detector according to the above

[16] , further comprising the step of removing the support member from the wiring substrate, the step of removing the support member being performed after the step of joining the photosemiconductor element and the scintillator unit." According to this method for manufacturing a radiation detector, it is possible to simplify the configuration of the radiation detector.

[0026] A method for manufacturing a radiation detector according to one aspect of the present disclosure includes the steps of:

[18] "preparing an optical semiconductor element including a semiconductor layer constituting a light receiving region, a scintillator unit, and a bonding film; arranging the bonding film in a region that is located on one side of the optical semiconductor element in a first direction parallel to a thickness direction of the semiconductor layer and that overlaps with the light receiving region when viewed from the first direction; and arranging the scintillator unit on the optical semiconductor element so as to face the optical semiconductor element across the region in the first direction; and bonding the optical semiconductor element to the scintillator unit by the bonding film. and bonding a substrate and the scintillator unit to the scintillator, wherein the scintillator unit has a scintillator corresponding to the light-receiving region, the light-receiving region has a plurality of light-receiving sections connected in parallel with each other, each of the plurality of light-receiving sections includes an avalanche photodiode operating in Geiger mode and a quenching element connected in series with the avalanche photodiode, the refractive index of the scintillator being 1.80 or more and 2.35 or less, and the refractive index of the bonding film being 1.60 or more and 2.00 or less.

[0027] According to the above-described method for manufacturing a radiation detector, the refractive index of the scintillator is 1.80 or more and 2.35 or less, and the refractive index of the bonding film is 1.60 or more and 2.00 or less, so that reflection of light emitted from the scintillator at the interface between the scintillator and the bonding film can be suppressed, and as a result, a decrease in radiation detection efficiency can be suppressed. Furthermore, according to the above-described method for manufacturing a radiation detector, for example, even without using a support member, variation in the thickness of the bonding film between the light-receiving region and the scintillator can be suppressed, and as a result, variation in radiation detection efficiency can be suppressed. As described above, according to the above-described method for manufacturing a radiation detector, a stable improvement in radiation detection efficiency can be achieved.

[0028] According to the present disclosure, it is possible to provide a radiation detector, a photodetector, and a method for manufacturing a radiation detector that can stably improve radiation detection efficiency.

[0029] FIG. 1 is a cross-sectional view of a radiation detector of one embodiment. FIG. 2 is a cross-sectional view of a portion of the radiation detector shown in FIG. 1. FIG. 3 is a plan view of the light-receiving region shown in FIG. 2. FIG. 4 is a cross-sectional view of a portion of the photodetector shown in FIG. 2. FIG. 5 is a circuit diagram of the optical semiconductor element shown in FIG. 2. FIG. 6 is a cross-sectional view of a portion of a radiation detector of a first modified example. FIG. 7 is a cross-sectional view of a portion of a radiation detector of a second modified example. FIG. 8 is a cross-sectional view for explaining a first example of a method for manufacturing a radiation detector. FIG. 9 is a cross-sectional view for explaining the first example of a method for manufacturing a radiation detector. FIG. 10 is a cross-sectional view for explaining the first example of a method for manufacturing a radiation detector. FIG. 11 is a cross-sectional view for explaining the first example of a method for manufacturing a radiation detector. FIG. 12 is a cross-sectional view for explaining a second example of a method for manufacturing a radiation detector. FIG. 13 is a cross-sectional view for explaining a third example of a method for manufacturing a radiation detector. FIG. 14 is a cross-sectional view for explaining the third example of a method for manufacturing a radiation detector. FIG. 15 is a cross-sectional view for explaining a fourth example of a method for manufacturing a radiation detector. FIG. 16 is a cross-sectional view for explaining the fourth example of a method for manufacturing a radiation detector.

[0030] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be omitted. [Configuration of the radiation detector]

[0031] 1 and 2, the radiation detector 1 includes a plurality of photodetectors 2, a scintillator unit 3, a plurality of wiring boards 4, a plurality of wires 5, a protective member 6, and a wiring board 7. In the following description, a direction parallel to the thickness direction of the wiring board 4 is referred to as the Z-axis direction (first direction), a direction perpendicular to the Z-axis direction is referred to as the X-axis direction (second direction), and a direction perpendicular to both the Z-axis direction and the X-axis direction is referred to as the Y-axis direction. Note that the protective member 6 is not shown in FIG. 2.

[0032] The wiring board 4 has a front surface 4a and a back surface 4b. In this embodiment, a plurality of photodetectors 2 are mounted on the front surface 4a of one wiring board 4. The plurality of photodetectors 2 are arranged in a matrix with the X-axis direction as the row direction and the Y-axis direction as the column direction. A cathode electrode 41 is provided on the front surface 4a of the wiring board 4, and each of the plurality of photodetectors 2 is fixed to the cathode electrode 41. The wiring board 4 is fixed to the wiring board 7 via a solder member S provided on the back surface 4b.

[0033] Each photodetector 2 has an optical semiconductor element 11, a support member 12, and a joining member 13. In this embodiment, the scintillator unit 3 is joined to each of the multiple photodetectors 2 by the joining member 13 so that one scintillator 31 included in the scintillator unit 3 corresponds to one optical semiconductor element 11. The correspondence between the scintillators 31 and the optical semiconductor elements 11 does not have to be the correspondence described above, and three scintillators 31 may correspond to two optical semiconductor elements 11.

[0034] The optical semiconductor element 11 includes a semiconductor layer 14, a first insulating layer 15, and a wiring layer 16. The thickness directions of the semiconductor layer 14, the first insulating layer 15, and the wiring layer 16 are parallel to the Z-axis direction. The optical semiconductor element 11 has, for example, a rectangular shape when viewed from the Z-axis direction. The semiconductor layer 14 has a front surface 14a and a back surface 14b. The first insulating layer 15 is formed on the front surface 14a. The wiring layer 16 is formed on the surface of the first insulating layer 15 opposite the semiconductor layer 14. In the optical semiconductor element 11, a cathode electrode 17 is provided on the back surface 14b of the semiconductor layer 14. The optical semiconductor element 11 is disposed on the cathode electrode 41 of the wiring substrate 4 so that the cathode electrode 17 faces the cathode electrode 41 of the wiring substrate 4. The cathode electrode 17 of the optical semiconductor element 11 and the cathode electrode 41 of the wiring substrate 4 are fixed to each other by a conductive adhesive C, for example, silver paste. In this embodiment, a plurality of optical semiconductor elements 11 are mounted on the surface 4a of one wiring board 4. That is, each optical semiconductor element 11 is directly mounted on the wiring board 4 and indirectly mounted on the wiring board 7.

[0035] Two anode electrodes 18 are provided on the wiring layer 16, and the two anode electrodes 18 are arranged near the outer edges of the optical semiconductor element 11 when viewed in the Z-axis direction. Specifically, each of the two anode electrodes 18 is arranged near each of both ends of the optical semiconductor element 11 in the X-axis direction. Two wires 5 connect each of the two anode electrodes 18 to an anode electrode 42 via the side of the optical semiconductor element 11. In other words, the wires 5 connect the optical semiconductor element 11 to the wiring substrate 4. As shown in FIG. 1 , pulse signals from the anode electrodes 18 of two adjacent optical semiconductor elements 11 are output to the individual anode electrodes 42. In FIG. 1 , pulse signals from the anode electrodes 18 of two adjacent optical semiconductor elements 11 are output to the individual anode electrodes 42 arranged in the Y-axis direction. The multiple wires 5, cathode electrodes 17, 41, and anode electrodes 18, 42 are covered by a protective member 6. The material of the protective member 6 is, for example, a resin material such as epoxy resin or silicone resin.

[0036] The semiconductor layer 14 and the wiring layer 16 constitute a light-receiving region 19. In this embodiment, each optical semiconductor element 11 has one light-receiving region 19, but each optical semiconductor element 11 may have multiple light-receiving regions 19. The light-receiving region 19 has multiple light-receiving sections 20, and as shown in Fig. 3, the multiple light-receiving sections 20 are arranged in a matrix with the X-axis direction as the row direction and the Y-axis direction as the column direction. Note that the multiple light-receiving sections 20 may be arranged in only one of the X-axis direction and the Y-axis direction.

[0037] A region R1 is disposed on one side (the scintillator unit 3 side) of the optical semiconductor element 11 in the Z-axis direction. The region R1 overlaps with the light receiving region 19 (plurality of light receiving sections 20) when viewed from the Z-axis direction. The bonding member 13 described above is disposed in the region R1. Each light receiving section 20 is a SPAD (Single Photon Avalanche Diode), and the optical semiconductor element 11 is a SiPM (Silicon Photomultiplier) in which one channel is formed by one light receiving region 19.

[0038] The multiple light receiving sections 20 include multiple first light receiving sections 20A arranged in the effective region R2 and multiple second light receiving sections 20B arranged in an outer edge region R3 that surrounds the effective region R2 when viewed from the Z-axis direction. Both the effective region R2 and the outer edge region R3 are regions of the optical semiconductor element 11. For example, the effective region R2 is a rectangular region located in the central portion of the optical semiconductor element 11 when viewed from the Z-axis direction, and the outer edge region R3 is a frame-shaped region located along the outer edge of the rectangular region when viewed from the Z-axis direction. In this embodiment, the multiple first light receiving sections 20A are located in the central portion of the optical semiconductor element 11 when viewed from the Z-axis direction, and the multiple second light receiving sections 20B are arranged to surround the multiple first light receiving sections 20A when viewed from the Z-axis direction. As an example, when viewed from the Z-axis direction, region R1 overlaps the entire effective region R2 but does not overlap with the outer edge region R3. That is, the region R1 is an area disposed directly above the effective region R2.

[0039] 4 and 5 , the optical semiconductor element 11 will be described in detail. The semiconductor layer 14 includes an N-type semiconductor region 141, a P-type semiconductor region 142, and a P+-type semiconductor region 143 for each light receiving section 20. The N-type semiconductor region 141 extends across the multiple light receiving sections 20. The P-type semiconductor region 142 is formed within the N-type semiconductor region 141 along the surface 14a of the semiconductor layer 14, and forms a PN junction with the N-type semiconductor region 141. The P+-type semiconductor region 143 is formed within the P-type semiconductor region 142 along the surface 14a of the semiconductor layer 14. In each light receiving section 20, the N-type semiconductor region 141, the P-type semiconductor region 142, and the P+-type semiconductor region 143 form an APD (avalanche photodiode) 21. The semiconductor layer 14 is made of, for example, silicon. In the semiconductor layer 14, the P-type impurities are, for example, Group 3 elements such as B, and the N-type impurities are, for example, Group 5 elements such as N, P, and As.

[0040] The surface 14a of the semiconductor layer 14 is composed of the surface of the N-type semiconductor region 141, the surface of the P-type semiconductor region 142, and the surface of the P+-type semiconductor region 143. On the surface 14a of the semiconductor layer 14, the surfaces of the N-type semiconductor region 141, the P-type semiconductor region 142, and the P+-type semiconductor region 143 are flush with each other. On the other hand, the back surface 14b of the semiconductor layer 14 is composed of the back surface of the N-type semiconductor region 141 opposite to the above-mentioned surface. The above-mentioned cathode electrode 17 is provided on the back surface of the N-type semiconductor region 141, and the cathode electrode 17 is electrically connected to the N-type semiconductor region 141.

[0041] The semiconductor layer 14 has trenches 14c. The trenches 14c extend so as to separate the P-type semiconductor regions 142 from one another. The trenches 14c open to the surface 14a of the semiconductor layer 14. The depth of the trenches 14c from the surface 14a is greater than the depth of the P-type semiconductor regions 142 from the surface 14a. In each light receiving section 20, a portion of the N-type semiconductor region 141 is disposed between the P-type semiconductor region 142 and the trenches 14c. An insulating region 144 is formed on the inner surface of the trenches 14c. The insulating region 144 is made of, for example, SiO ２ A metal member 145 is disposed in the trench 14c. The material of the metal member 145 is W, for example.

[0042] The first insulating layer 15 is disposed on the semiconductor layer 14 on the region R1 side. The first insulating layer 15 is formed on the surface 14a of the semiconductor layer 14 so as to contact the surfaces of the N-type semiconductor region 141, the P-type semiconductor region 142, and the P+-type semiconductor region 143. The material of the first insulating layer 15 is, for example, SiN. The thickness of the first insulating layer 15 in the Z-axis direction is, for example, 1 / (4n) of the wavelength of the light emitted from the scintillator 31, where n is a natural number greater than or equal to 1. In this case, the thickness is, for example, 50 nm.

[0043] The wiring layer 16 has a plurality of quenching resistors 22, a plurality of through electrodes 23, a readout wiring 24, and a second insulating layer 25. In the example of Fig. 4, one quenching resistor 22 out of the plurality of quenching resistors 22 and one through electrode 23 out of the plurality of through electrodes 23 are shown. The quenching resistor 22, the through electrode 23, and the readout wiring 24 are formed in the second insulating layer 25.

[0044] One quenching resistor 22 and one APD 21 constitute one light receiving unit 20. In each light receiving unit 20, the quenching resistor 22 extends along the outer edge of the P+ type semiconductor region 143 when viewed from the Z-axis direction. One end 22a of the quenching resistor 22 is electrically connected to the P+ type semiconductor region 143 via a through electrode 23. The through electrode 23 penetrates the first insulating layer 15 and reaches the P+ type semiconductor region 143. The quenching resistor 22 may be in direct contact with the P+ type semiconductor region 143. The other end (not shown) of the quenching resistor 22 is electrically connected to the readout wiring 24. The quenching resistor 22 is made of a material such as NiCr, SiCr, TaNi, or FeCr. The through electrode 23 is made of a material such as Al.

[0045] The readout wiring 24 has a plurality of openings 24a. In each light receiving unit 20, the opening 24a includes each P+ type semiconductor region 143 and the quenching resistor 22 when viewed from the Z-axis direction. The readout wiring 24 extends across the plurality of light receiving units 20. The readout wiring 24 is electrically connected to the corresponding anode electrode 18 (see FIG. 2). The material of the readout wiring 24 is, for example, Al.

[0046] 5 is a circuit diagram of the optical semiconductor element 11. As shown in FIG. 5, the light-receiving region 19 has a plurality of light-receiving sections 20 connected in parallel to one another. Each light-receiving section 20 includes an APD 21 and a quenching resistor 22 connected in series with the APD 21. The anode of each APD 21 is electrically connected to the anode electrode 18 via the corresponding quenching resistor 22, and the cathode of each APD 21 is electrically connected to the cathode electrode 17. Note that the light-receiving region 19 may be configured with a plurality of channels, each including a plurality of light-receiving sections 20 connected in parallel.

[0047] In the optical semiconductor device 11, each APD 21 operates in the Geiger mode. In the Geiger mode, a reverse voltage (reverse bias voltage) greater than the breakdown voltage of the APD 21 is applied to each APD 21. As an example, when the anode electrode 18 is grounded via a resistor R, a positive voltage V greater than the breakdown voltage of the APD 21 is applied to the cathode electrode 17.

[0048] When light is incident on at least one of the APDs 21 while the APDs 21 are operating in Geiger mode, charges are generated by photoelectric conversion in the APD 21, and the generated charges are amplified by avalanche multiplication. The charges amplified in the APD 21 are output to the anode electrode 18 via the corresponding quenching resistor 22, and are then output from the anode electrode 18 to an external signal processing unit as a pulse signal.

[0049] The second insulating layer 25 is disposed on the first insulating layer 15 on the region R1 side. The second insulating layer 25 is made up of a plurality of insulating films and extends across the plurality of light receiving sections 20. The material of each insulating film is, for example, SiO ２ The second insulating layer 25 may be formed of a single insulating film.

[0050] The second insulating layer 25 has a plurality of first openings 25a and a plurality of second openings 25b. The plurality of first openings 25a and the plurality of second openings 25b are open on both sides in the Z-axis direction. When viewed from the Z-axis direction, each of the plurality of first openings 25a overlaps with a corresponding one of the plurality of first light receiving units 20A. When viewed from the Z-axis direction, each of the plurality of first openings 25a only needs to overlap with at least the APD 21. When viewed from the Z-axis direction, each of the plurality of second openings 25b overlaps with a corresponding one of the plurality of second light receiving units 20B. When viewed from the Z-axis direction, each of the plurality of second openings 25b only needs to overlap with at least the APD 21. Similar to the plurality of light receiving units 20, the plurality of first openings 25a and the plurality of second openings 25b are arranged in a matrix with the X-axis direction as the row direction and the Y-axis direction as the column direction as a whole. The second openings 25b are arranged to surround the first openings 25a when viewed from the Z-axis direction.

[0051] Each of the plurality of first openings 25a and each of the plurality of second openings 25b penetrates the wiring layer 16 (second insulating layer 25) along the Z-axis direction. As a result, a portion of the surface of the first insulating layer 15 is exposed to the outside through the first openings 25a and the second openings 25b. A portion of the bonding member 13 is disposed in the first opening 25a, and a portion of the support member 12 is disposed in the second opening 25b.

[0052] The scintillator unit 3 will be described in detail with reference to FIGS. 1 and 2 . The scintillator unit 3 is disposed so as to face the optical semiconductor element 11 via the region R1 in the Z-axis direction. Specifically, the scintillator unit 3 faces the surface 14a of the semiconductor layer 14 via the region R1 in the Z-axis direction. The scintillator unit 3 includes a plurality of scintillators 31 and a light reflecting member 32. The plurality of scintillators 31 are aligned in a row in the X-axis direction. Each of the plurality of scintillators 31 corresponds to a respective light receiving region 19 of the plurality of optical semiconductor elements 11. Specifically, each scintillator 31 is disposed on each light receiving region 19 via a bonding member 13. The shape of each scintillator 31 is, for example, a rectangular parallelepiped with the Z-axis direction as the longitudinal direction. The cross-sectional shape of each scintillator 31 perpendicular to the Z-axis direction is, for example, a square. The material of each scintillator 31 is, for example, NaI:Tl, Gd ２ SiO ５ : Ce, Bi ４ Ge ３ O １２ , LuSiO ５ : Ce, etc.

[0053] The light reflecting member 32 covers the surface 31a of each scintillator 31 except for the surface 31b facing the optical semiconductor element 11. When radiation (e.g., X-rays, gamma rays, etc.) is incident on a certain scintillator 31 and light is emitted from that scintillator 31, the light travels toward the surface 31b or is reflected by the light reflecting member 32, and is then emitted from the surface 31b. The material of the light reflecting member 32 is, for example, titanium oxide.

[0054] The support member 12 and the joining member 13 will be described in detail with reference to FIGS. 1, 2, and 4. The support member 12 is disposed between the optical semiconductor element 11 and the scintillator unit 3 and supports the scintillator unit 3. In this embodiment, the support member 12 is disposed between the second insulating layer 25 and the scintillator unit 3. The support member 12 has a support surface 12a that supports the scintillator unit 3. The support surface 12a is in contact with the scintillator 31. The support surface 12a may also be in contact with the light reflecting member 32. The support member 12 is disposed on both sides of the region R1 in the X-axis direction. In this embodiment, the support member 12 is a frame-shaped member that surrounds the region R1 when viewed from the Z-axis direction. The region R1 is also a space defined by the optical semiconductor element 11, the scintillator unit 3 (scintillator 31), and the support member 12. The support member 12 is positioned so as to overlap with the plurality of second openings 25b (the plurality of second light receiving sections 20B) when viewed from the Z-axis direction. A portion 12b of the support member 12 is disposed in each second opening 25b. The portion 12b of the support member 12 corresponds to the base end of the support member 12. The portion 12b of the support member 12 is in contact with the inner surface of the second opening 25b and the first insulating layer 15. By disposing the portion 12b of the support member 12 in the second opening 25b in this manner, the support member 12 is held by the wiring layer 16 (second insulating layer 25). The other portion of the support member 12 is disposed on the wiring layer 16 (second insulating layer 25). The material of the support member 12 is, for example, a resin material such as novolac epoxy resin. The material of the support member 12 may also be a conductive material such as a Cu pillar.

[0055] The anode electrode 18 is provided on the wiring layer 16 outside the support member 12 in the X-axis direction. Each of the two wires 5 connects the anode electrode 18 of the optical semiconductor element 11 to the anode electrode 42 of the wiring substrate 4 outside the support member 12 in the X-axis direction. The height H1 from the surface 14a of the semiconductor layer 14 to the support surface 12a of the support member 12 in the Z-axis direction is greater than the height H2 from the portion 5a of the wire 5 that is farthest from the surface 14a of the semiconductor layer 14 in the Z-axis direction. In other words, when the support member 12 supports the scintillator unit 3, the scintillator unit 3 does not contact the wire 5. The height H1 may be 1000 μm or less, or may be 200 μm or less. The protective member 6 covers the multiple wires 5 outside the support member 12 in the X-axis direction and contacts the support member 12. When the support member 12 is a frame-shaped member as in this embodiment, the protection member 6 may be arranged outside the support member 12 so as to surround the support member 12 when viewed from the Z-axis direction.

[0056] The bonding member 13 is disposed in the region R1 and bonds the optical semiconductor element 11 and the scintillator unit 3. The bonding member 13 contacts each of the optical semiconductor element 11, the support member 12, and the scintillator unit 3 (scintillator 31) in the region R1. The bonding member 13 fills the region R1. The bonding member 13 may contact the light reflecting member 32. The thickness of the bonding member 13 in the Z-axis direction may be 1000 μm or less, or may be 200 μm or less. The bonding member 13 is disposed in a position overlapping with the multiple first openings 25a (the multiple first light receiving sections 20A) when viewed from the Z-axis direction. A portion 13a of the bonding member 13 is disposed in each first opening 25a. The portion 13a of the bonding member 13 contacts each of the inner surfaces of the first openings 25a and the first insulating layer 15. By disposing a portion 13a of the bonding member 13 in the first opening 25a in this manner, a portion of the light emitted from the scintillator 31 can enter the first insulating layer 15 through the first opening 25a without entering the second insulating layer 25. The other portion of the bonding member 13 is disposed on the wiring layer 16 (second insulating layer 25). The material of the bonding member 13 is, for example, a resin material based on polyimide, polycarbonate, polyurethane, or the like, with an adjusted refractive index, or a resin material mixed with nano-sized particles of an inorganic material such as titanium oxide, barium tantalate, or hafnium oxide. As shown in FIG. 1, a portion of the bonding member 13 may be disposed between the scintillator unit 3 and the protective member 6 on the outside of the support member 12. [Refractive Index]

[0057] Next, the refractive index of each component of the radiation detector 1 will be described. Here, the refractive index refers to the refractive index for light with a wavelength of 400 nm. The refractive index of the scintillator 31 is 1.80 or more and 2.35 or less. The refractive index of the bonding member 13 is 1.60 or more and 2.00 or less. By reducing the difference between the refractive index of the scintillator 31 and the refractive index of the bonding member 13 in this manner, reflection of light emitted from the scintillator 31 at the interface between the scintillator 31 and the bonding member 13 can be suppressed. From the viewpoint of further suppressing light reflection at the interface, the absolute value of the difference between the refractive index of the scintillator 31 and the refractive index of the bonding member 13 may be 0.2 or less. The refractive index of the semiconductor layer 14 is 5.57, for example, 3.00 or more and 6.00 or less. The refractive index of the first insulating layer 15 is approximately 2.00 when the material of the first insulating layer 15 is SiN. The refractive index of the first insulating layer 15 may be higher than that of the bonding member 13 and lower than that of the semiconductor layer 14. In this case, it is possible to suppress the reflection of light at the interface between the bonding member 13 and the first insulating layer 15 and at the interface between the first insulating layer 15 and the semiconductor layer 14. The refractive index of the second insulating layer 25 is set to 0.05 when the material of the second insulating layer 25 is SiO. ２ , the refractive index is approximately 1.47. The refractive index of the first insulating layer 15 may be higher than the refractive index of the second insulating layer 25. In this case, the difference between the refractive index of the bonding member 13 and the first insulating layer 15 can be made smaller than the difference between the refractive index of the bonding member 13 and the second insulating layer 25. This makes it possible to further suppress light reflection at the interface between the bonding member 13 and the first insulating layer 15.

[0058] In the radiation detector 1 configured as described above, radiation is incident on the scintillator 31, causing the scintillator 31 to emit light. Most of the light emitted from the surface 31b of the scintillator 31 is incident on the bonding member 13. A portion of the light incident on the bonding member 13 passes through the portion 13a of the bonding member 13 arranged in the first opening 25a, enters the first insulating layer 15, and is then incident on the multiple first light receiving sections 20A arranged in the effective region R2. Charges are generated by photoelectric conversion in the APD 21 in each first light receiving section 20A, and the generated charges are amplified by avalanche multiplication. The charges amplified in the APD 21 are output to the anode electrode 18 via the corresponding quenching resistor 22, and are output from the anode electrode 18 to an external signal processing unit as a pulse signal.

[0059] As described above, in the radiation detector 1, light generated in the scintillator 31 is detected by at least the plurality of first light receiving sections 20A arranged in the effective region R2. In other words, the effective region R2 is a region that has the function of detecting light generated in the scintillator 31. In the radiation detector 1, light generated in the scintillator 31 may be detected by the plurality of second light receiving sections 20B arranged in the outer edge region R3. However, because the support member 12 is arranged in a position that overlaps with the plurality of second light receiving sections 20B, the outer edge region R3 does not need to function as a region that detects light generated in the scintillator 31. In other words, in the radiation detector 1, light generated in the scintillator 31 may be detected only by the plurality of first light receiving sections 20A arranged in the effective region R2. [Actions and Effects]

[0060] In the radiation detector 1, a bonding member 13 is disposed in a region R1 that is located on one side of the optical semiconductor element 11 in the Z-axis direction parallel to the thickness direction of the semiconductor layer 14 and overlaps with the light receiving region 19 when viewed from the Z-axis direction. In the region R1, the bonding member 13 is in contact with both the optical semiconductor element 11 and the scintillator unit 3. In this state, the refractive index of the scintillator 31 is 1.80 or more and 2.35 or less, and the refractive index of the bonding member 13 is 1.60 or more and 2.00 or less. This prevents light emitted from the scintillator 31 from being reflected at the interface between the scintillator 31 and the bonding member 13, thereby preventing a decrease in radiation detection efficiency. In the radiation detector 1, support members 12 that support the scintillator unit 3 are disposed on both sides of the region R1 in the X-axis direction, and the bonding members 13 are in contact with the support members 12 in the region R1. This makes it possible to suppress variations in the thickness of the bonding member 13 between the light receiving region 19 and the scintillator 31, and as a result, to suppress variations in the radiation detection efficiency. As described above, the radiation detector 1 can stably improve the radiation detection efficiency.

[0061] The radiation detector 1 uses a bonding member 13 with a relatively high refractive index. If the refractive index of the bonding member 13 becomes high, the transmittance of light (for example, light with a wavelength of 400 nm or more) through the bonding member 13 may decrease. For example, if the refractive index becomes high, the dielectric constant also increases, and as a result, the bonding member 13 may contain many functional groups that absorb ultraviolet light. In addition, if the bonding member 13 contains TiO ２ When an inorganic material such as fluorine or the like is mixed into the bonding member 13, there is a risk that the inorganic material will absorb ultraviolet light. From the viewpoint of suppressing light absorption by the bonding member 13, it is desirable to reduce the thickness of the bonding member 13. In the radiation detector 1, the support member 12 maintains a constant distance between the light receiving region 19 and the scintillator 31, so the thickness of the bonding member 13 disposed in region R1 can be easily adjusted. As a result, it is easy to adjust the thickness of the bonding member 13 to a desired thickness (e.g., a thickness that allows light absorption by the bonding member 13).

[0062] In the radiation detector 1, one scintillator 31 and one optical semiconductor element 11 (one light-receiving region 19) correspond to each other, and there are a plurality of pairs of corresponding scintillators 31 and light-receiving regions 19. In the radiation detector 1, it is desirable to make the radiation detection efficiency uniform in each pair. As described above, in the radiation detector 1, the thickness of the bonding member 13 arranged in region R1 can be easily adjusted, and therefore the thickness of the bonding member 13 in each pair can be easily made approximately the same. This makes it possible to suppress variation in the radiation detection efficiency in each pair in the radiation detector 1.

[0063] In the radiation detector 1, the optical semiconductor element 11 includes a first insulating layer 15 disposed on the semiconductor layer 14 on the region R1 side, and the refractive index of the first insulating layer 15 is higher than the refractive index of the bonding member 13 and lower than the refractive index of the semiconductor layer 14. This makes it possible to suppress reflection of light emitted from the scintillator 31 at the interface between the bonding member 13 and the first insulating layer 15 and the interface between the first insulating layer 15 and the semiconductor layer 14, thereby further improving the radiation detection efficiency.

[0064] In the radiation detector 1, the optical semiconductor element 11 includes a second insulating layer 25 arranged on the first insulating layer 15 on the region R1 side, the second insulating layer 25 covering the quenching resistor 22, the second insulating layer 25 having a plurality of first openings 25a opening on both sides in the Z-axis direction, each of the plurality of first openings 25a overlapping with a respective one of the plurality of first light receiving sections 20A arranged in the effective region R2 among the plurality of light receiving sections 20 when viewed from the Z-axis direction, and a part 13a of the bonding member 13 is arranged in each of the plurality of first openings 25a, and the part 13a of the bonding member 13 is in contact with the first insulating layer 15. As a result, the light emitted from the scintillator 31 enters the first insulating layer 15 through the first opening 25a provided in the second insulating layer 25 for protecting the quenching resistor 22, thereby preventing the light emitted from the scintillator 31 from being reflected at the interface between the joining member 13 and the second insulating layer 25, thereby further improving the radiation detection efficiency.

[0065] In the radiation detector 1, the support member 12 is disposed between the second insulating layer 25 and the scintillator unit 3, the second insulating layer 25 has a plurality of second openings 25b that open on both sides in the Z-axis direction, and a part 12b of the support member 12 is disposed in each of the plurality of second openings 25b. This makes it possible to accurately and stably maintain the distance between the light-receiving region 19 and the scintillator 31 and the thickness of the joining member 13 between the light-receiving region 19 and the scintillator 31.

[0066] In the radiation detector 1, when viewed in the Z-axis direction, each of the second openings 25b overlaps with a corresponding one of the second light receiving sections 20B that are arranged outside the effective region R2 of the multiple light receiving sections 20. This makes it possible to reduce the size of the radiation detector 1 when viewed in the Z-axis direction, even when multiple second light receiving sections 20B are provided.

[0067] In the radiation detector 1, the multiple second light receiving sections 20B are arranged in an outer edge region R3 that surrounds the effective region R2 when viewed from the Z-axis direction, thereby making it possible to prevent a decrease in the aperture ratio of the light receiving region 19.

[0068] The radiation detector 1 includes a wiring board 4 on which a plurality of photodetectors 2 arranged in the X-axis direction and the Y-axis direction are mounted, a plurality of wires 5, and a protective member 6, and each of the plurality of photodetectors 2 includes an optical semiconductor element 11, a support member 12 arranged between the optical semiconductor element 11 and the scintillator unit 3, and a bonding member 13, and each of the plurality of wires 5 connects the optical semiconductor element 11 to the wiring board 4 on the outside of the support member 12 in the X-axis direction, and the protective member 6 covers the plurality of wires 5 on the outside of the support member 12 in the X-axis direction. This makes it possible to accurately and stably maintain the distance between the light-receiving region 19 and the scintillator 31 and the thickness of the bonding member 13 between the light-receiving region 19 and the scintillator 31 in each of the plurality of photodetectors 2.

[0069] In the radiation detector 1, the absolute value of the difference between the refractive index of the scintillator 31 and the refractive index of the bonding member 13 is 0.2 or less. Because the difference in refractive index between the bonding member 13 and the scintillator 31 is smaller, reflection of light emitted from the scintillator 31 at the interface between the scintillator 31 and the bonding member 13 can be further suppressed.

[0070] In the radiation detector 1, the semiconductor layer 14 has a surface 14a that faces the scintillator unit 3 across the region R1 in the Z-axis direction, the support member 12 has a support surface 12a that supports the scintillator unit 3, and the height from the surface 4a to the support surface 12a in the Z-axis direction is, for example, 200 μm or less. This makes it possible to maintain the thickness of the joining member 13 between the light-receiving region 19 and the scintillator 31 at 200 μm or less, and to prevent light emitted from the scintillator 31 from being absorbed by the joining member 13.

[0071] The photodetector 2 includes an optical semiconductor element 11 including a semiconductor layer 14 that constitutes a light-receiving region 19, and support members 12 that are located on one side of the optical semiconductor element 11 in the Z-axis direction and on both sides in the X-axis direction of a region R1 that overlaps with the light-receiving region 19 when viewed from the Z-axis direction. For example, by placing the scintillator unit 3 on the support member 12 so that the scintillator 31 faces the light-receiving region 19, and by placing a bonding member 13 between the light-receiving region 19 and the scintillator 31, it is possible to obtain a radiation detector 1 that can maintain the distance between the light-receiving region 19 and the scintillator 31 and the thickness of the bonding member 13 between the light-receiving region 19 and the scintillator 31. [Radiation Detector of First Modification]

[0072] 6, the radiation detector 1 of the first modified example differs from the radiation detector 1 of the above embodiment mainly in that the optical semiconductor element 11 has an opening 11a. The radiation detector 1 of the first modified example will be described below, focusing on the differences from the radiation detector 1 of the above embodiment.

[0073] The optical semiconductor element 11 has openings 11a (third openings) that open on both sides in the Z-axis direction. When viewed from the Z-axis direction, the opening 11a is located in the center of the optical semiconductor element 11 and overlaps the bonding member 13. The opening 11a penetrates the wiring layer 16 (second insulating layer 25), the semiconductor layer 14, and the cathode electrode 17 along the Z-axis direction. The cathode electrode 41 and the conductive adhesive C each have an opening that communicates with the opening 11a. This exposes a portion of the surface 4a of the wiring substrate 4 to the outside.

[0074] The anode electrode 42 is provided on that portion of the surface 4a. The anode electrode 18 is disposed near the opening 11a when viewed from the Z-axis direction. The wire 5 passes through the opening 11a and connects the anode electrode 18 of the optical semiconductor element 11 to the anode electrode 42 of the wiring substrate 4. A portion 13b of the bonding member 13 is disposed in the opening 11a and is in contact with a portion of the surface 4a of the wiring substrate 4. The bonding member 13 covers the anode electrodes 18, 42 and the wire 5.

[0075] As with the above-described embodiment, this first modification also makes it possible to stably improve the radiation detection efficiency. Furthermore, according to the first modification, by disposing a part 13b of the bonding member 13 within the opening 11a of the optical semiconductor element 11, it is possible to protect the wire 5 and to accurately and stably maintain the thickness of the bonding member 13 between the light receiving region 19 and the scintillator 31. [Radiation detector of second modification]

[0076] 7, the radiation detector 1 of the second modified example differs from the radiation detector 1 of the first modified example mainly in that a support member 12 is attached to a wiring board 4. The radiation detector 1 of the second modified example will be described below, focusing on the differences from the radiation detector 1 of the first modified example.

[0077] The support member 12 is attached to the surface 4a of the wiring substrate 4 at positions on both sides of the optical semiconductor element 11 in the X-axis direction. In the second modification, the support member 12 is a frame-shaped member that surrounds the optical semiconductor element 11 when viewed from the Z-axis direction. In the second modification, unlike the above embodiment and the first modification, the support member 12 is not positioned so as to overlap with the plurality of second light receiving portions 20B, and therefore the outer edge region R3 also functions as a region that detects light generated in the scintillator 31. In other words, in the second modification, it can be said that all of the plurality of light receiving portions 20 are positioned in the effective region. This allows light generated in the scintillator 31 to be detected over a wider area.

[0078] Part 13c of joining member 13 is disposed between the side of optical semiconductor element 11 and support member 12, joining optical semiconductor element 11 and support member 12. This makes it possible to more reliably maintain the position of support member 12 constant.

[0079] As with the above embodiment, this second modification also makes it possible to stably improve the radiation detection efficiency. Furthermore, the position of the support member 12 can be adjusted depending on the mounting state of the optical semiconductor element 11 on the wiring board 4. [First Example of the Method for Manufacturing a Radiation Detector]

[0080] A first example of a method for manufacturing a radiation detector 1 will be described with reference to Figures 8 to 11. First, an optical semiconductor element 11 including a semiconductor layer 14 constituting a light receiving region 19, a scintillator unit 3, and a bonding material BM are prepared. The optical semiconductor element 11 shown in Figure 8 differs from the optical semiconductor element 11 shown in Figure 4 in that it does not have a plurality of first openings 25a and a plurality of second openings 25b. The bonding material BM is a liquid material intended to become the bonding member 13, and is, for example, a resin material based on polyimide, polycarbonate, polyurethane, or the like, with an adjusted refractive index, or a resin material mixed with nano-sized particles of an inorganic material such as titanium oxide, barium tantalate, or hafnium oxide.

[0081] 9A, a plurality of first openings 25a and a plurality of second openings 25b are formed in the wiring layer 16 (second insulating layer 25). The first openings 25a and the second openings 25b are formed by, for example, plasma etching.

[0082] Next, as shown in (b) and (c) of Figure 9, support members 12 are arranged on both sides of region R1 in the X-axis direction. In the first example, the support members 12 are arranged so as to surround region R1 when viewed from the Z-axis direction. Specifically, first, a liquid resist RE is applied to the entire surface of the optical semiconductor element 11. At this time, a portion of the resist RE enters the first opening 25a and the second opening 25b. The resist RE is a material intended to become the support member 12, and is, for example, a resin material such as novolac epoxy resin. The liquid resist RE is hardened (e.g., photo-hardened with ultraviolet light, thermal hardening, etc.) to form a solid resist RE. Next, a portion RE1 of the solid resist RE located in region R1 is removed to form the support member 12. The portion RE1 is removed, for example, by dissolving it in an organic solvent. At this time, the portion of the resist RE that entered the first opening 25a is also removed. In this step, a portion RE2 of the solid resist RE that is disposed along the outer edge of optical semiconductor element 11 is also removed so that anode electrode 18 is exposed to the outside.

[0083] Next, as shown in Fig. 10(a), each optical semiconductor element 11 is mounted on the wiring board 4. Specifically, each optical semiconductor element 11 is fixed to each cathode electrode 41 provided on the wiring board 4 with a conductive adhesive C. Next, as shown in Fig. 10(b), the optical semiconductor element 11 and the wiring board 4 (anode electrode 42) are connected by a wire 5. Next, as shown in Fig. 10(c), the wire 5 is covered with a protective member 6.

[0084] 11(a), the wiring board 4 on which the optical semiconductor element 11 is mounted is fixed to the wiring board 7 with the solder member S. Next, as shown in FIG. 11(b), the scintillator unit 3 is placed on the support member 12 so as to face the optical semiconductor element 11 via the region R1 in the Z-axis direction. Next, a bonding material BM is introduced into the region R1 so as to contact the optical semiconductor element 11, the support member 12, and the scintillator unit 3 (scintillator 31). The introduced bonding material BM is cured (for example, photocured with ultraviolet light or the like, thermally cured, etc.) to form the bonding member 13. As a result, the optical semiconductor element 11 and the scintillator unit 3 are bonded together by the bonding member 13.

[0085] According to the first example of the method for manufacturing the radiation detector 1, it is possible to stably improve the radiation detection efficiency for the same reasons as those for the radiation detector 1 described above. Furthermore, for example, since the support member 12 can be formed in a semiconductor manufacturing process, it is possible to form the support member 12 with high precision. [Second Example of the Method for Manufacturing a Radiation Detector]

[0086] A second example of a method for manufacturing a radiation detector 1 will be described with reference to FIG. 12 . In the first example, the support member 12 was formed of resist RE. In the second example, the support member 12 is formed of a resin material introduced into a mold 8. Specifically, first, a mold 8 shown in FIG. 12A is prepared. The mold 8 includes a bottom wall 81, a protruding portion 82 protruding from the bottom wall 81, and a sidewall 83 surrounding the protruding portion 82 on the bottom wall 81. The sidewall 83 is a frame-shaped portion surrounding the protruding portion 82 when viewed from the Z-axis direction. Next, the optical semiconductor element 11 is mounted on the wiring substrate 4, and the optical semiconductor element 11 and the wiring substrate 4 are connected by wires 5. Next, the mold 8 is placed on the optical semiconductor element 11 so that the wires 5 and the anode electrode 42 are positioned between the protruding portion 82 and the sidewall 83. At this time, the protruding portion 82 is positioned in region R1 and contacts the surface of the wiring layer 16. The sidewalls 83 are in contact with the surface 4a of the wiring substrate 4. Next, a resin material (the material intended to become the support member 12) is introduced into the mold 8 so that the wires 5 and the anode electrodes 42 are covered with the resin material. The introduced resin material is cured (for example, by photocuring with ultraviolet light or the like, or by heat curing), and the mold 8 is removed from the optical semiconductor element 11, thereby forming the support member 12 shown in FIG. 12(b). The support member 12 covers the wires 5 and the anode electrodes 42.

[0087] According to the second example of the method for manufacturing the radiation detector 1, it is possible to stably improve the radiation detection efficiency for the same reasons as those for the radiation detector 1 described above. Furthermore, by using the mold 8, it is possible to easily form the support member 12. Furthermore, it is possible to easily form the support member 12 that has both the function of supporting the scintillator unit 3 and the function of protecting the wires 5. [Third Example of the Method for Manufacturing a Radiation Detector]

[0088] A third example of the method for manufacturing the radiation detector 1 will be described with reference to FIGS. 13 and 14 . In the first example, the support member 12 was formed on the optical semiconductor element 11 using the resist RE. In the third example, however, the support member 12 is attached to the wiring board 7. Specifically, as shown in FIG. 13A, the optical semiconductor element 11 is first mounted on the wiring board 4, and the optical semiconductor element 11 and the wiring board 4 are connected by wires 5. Next, the wiring board 4 on which the optical semiconductor element 11 is mounted is fixed to the wiring board 7 by the solder member S. Next, the support members 12 are attached to the wiring board 7 at positions on both sides of the optical semiconductor element 11 in the X-axis direction. In the third example, the support members 12 are disposed at positions on both sides of the wiring board 4 on which the optical semiconductor element 11 is mounted in the X-axis direction. The support members 12 shown in FIG. 13A are columnar members that sandwich the wiring board 4 on which the optical semiconductor element 11 is mounted in the X-axis direction. The support member 12 is inserted into, for example, an opening provided in the wiring board 7. The support member 12 may be a frame-shaped member. Next, as shown in FIG. 13B, the bonding material BM is introduced onto the wiring board 7 so that each component arranged on the wiring board 7 is covered with the bonding material BM. That is, in the third example, the bonding material BM is introduced over a wide region including the region R1. The bonding material BM may cover the support surface 12 a of the support member 12.

[0089] Next, as shown in Fig. 14(a), the scintillator unit 3 is placed on the support member 12 so as to face the optical semiconductor element 11. The introduced bonding material BM is then cured (for example, by photocuring with ultraviolet light or the like, or by heat curing), thereby forming the bonding member 13. This bonds the optical semiconductor element 11 and the scintillator unit 3 together with the bonding member 13. Next, as shown in Fig. 14(b), the support member 12 is removed from the wiring board 7. In other words, the radiation detector 1 manufactured according to the third example does not include the support member 12.

[0090] According to the third example of the method for manufacturing the radiation detector 1, it is possible to stably improve the radiation detection efficiency for the same reasons as for the radiation detector 1 described above. Also, the position of the support member 12 can be adjusted depending on the mounting state of the optical semiconductor element 11 on the wiring board 7. Furthermore, since the step of removing the support member 12 from the wiring board 7 is performed after the step of bonding the optical semiconductor element 11 and the scintillator unit 3, it is possible to simplify the configuration of the radiation detector 1 manufactured according to the third example. [Fourth Example of the Method for Manufacturing a Radiation Detector]

[0091] A fourth example of the method for manufacturing the radiation detector 1 will be described with reference to Figures 15 and 16. In the first example, the optical semiconductor element 11 and the scintillator unit 3 are bonded together using the bonding member 13. In the fourth example, however, the optical semiconductor element 11 and the scintillator unit 3 are bonded together using a bonding film 26. Specifically, a bonding film 26 having a refractive index of 1.60 or more and 2.00 or less is first prepared. The bonding film 26 is flexible. The bonding film 26 is made of, for example, a pressure-sensitive adhesive. The material of the bonding film 26 is, for example, a resin material based on polyimide, polycarbonate, polyurethane, or the like, with an adjusted refractive index, or a resin material mixed with nano-sized particles of an inorganic material such as titanium oxide, barium tantalate, or hafnium oxide.

[0092] Next, as shown in Fig. 15, the optical semiconductor element 11 is mounted on the wiring substrate 4. The optical semiconductor element 11 shown in Fig. 15 differs from the optical semiconductor element 11 shown in Figs. 6 and 7 mainly in that it does not have an opening 11a and that it has a through electrode 27. The through electrode 27 is provided in the semiconductor layer 14 and penetrates the semiconductor layer 14 along the Z-axis direction. The through electrode 27 is electrically connected to the anode electrode 18. An electrode E is provided on a portion of the surface of the through electrode 27. The electrode E is fixed to the anode electrode 42 by a conductive adhesive C. This electrically connects the anode electrode 18 and the anode electrode 42 via the through electrode 27.

[0093] 16 , a bonding film 26 is disposed in region R1, and the scintillator unit 3 is disposed on the optical semiconductor element 11 so as to face the optical semiconductor element 11 across region R1 in the Z-axis direction. This bonds the optical semiconductor element 11 and the scintillator unit 3 together with the bonding film 26. Portions of the bonding film 26 are disposed inside the first opening 25 a and the second opening 25 b and are in contact with the first insulating layer 15. When the bonding film 26 is in contact with the anode electrode 18, the wire 5 cannot be disposed within the bonding film 26, and therefore the wire 5 cannot be connected to the anode electrode 18. However, since the through electrode 27 is electrically connected to the anode electrode 18 within the semiconductor layer 14, the anode electrode 18 and the anode electrode 42 can be electrically connected without being affected by the bonding film 26.

[0094] According to the fourth example of the method for manufacturing the radiation detector 1, the refractive index of the scintillator 31 is 1.80 or more and 2.35 or less, and the refractive index of the bonding film 26 is 1.60 or more and 2.00 or less, so that it is possible to prevent light emitted from the scintillator 31 from being reflected at the interface between the scintillator 31 and the bonding film 26, and as a result, it is possible to prevent a decrease in the radiation detection efficiency. Furthermore, according to the fourth example of the method for manufacturing the radiation detector 1, for example, even without using the support member 12, it is possible to prevent variation in the thickness of the bonding film 26 between the light receiving region 19 and the scintillator 31, and as a result, it is possible to prevent variation in the radiation detection efficiency. As described above, according to the fourth example of the method for manufacturing the radiation detector 1, it is possible to achieve a stable improvement in the radiation detection efficiency. [Modification]

[0095] The present disclosure is not limited to the above-described embodiments. For example, in the above-described embodiments, the wiring layer 16 is disposed on the front surface 14a of the semiconductor layer 14. However, the wiring layer 16 may be disposed on the rear surface 14b of the semiconductor layer 14. In this case, the P-type semiconductor region 142 and the P+-type semiconductor region 143 may be disposed along the rear surface 14b of the semiconductor layer 14. That is, the optical semiconductor element 11 may be a back-illuminated type. When the optical semiconductor element 11 is a back-illuminated type, a circuit board may be directly bonded to the rear surface 14b of the semiconductor layer 14 via a wiring layer, and a quenching element may be formed within the circuit board. That is, in the radiation detector 1, active quenching may be performed by providing an element such as a transistor as the quenching element, rather than a quenching resistor 22 such as SiCr. In this case, the light receiving unit 20 may be configured to include the APD 21 and a quenching element formed within the circuit board. Furthermore, in the optical semiconductor element 11 functioning as a SiPM, each light receiving portion 20 may have another configuration, such as a configuration in which the N-type and P-type are reversed. As an example, the N-type semiconductor region 141, the P-type semiconductor region 142, and the P+-type semiconductor region 143 may be a P-type semiconductor region, an N-type semiconductor region, and an N-type semiconductor region, respectively. Furthermore, the material of the semiconductor layer 14 is not limited to silicon, and may be a compound semiconductor.

[0096] In the above embodiment, the support member 12 is a frame-shaped member, but the support member 12 may be a columnar member. In this case, multiple support members 12 may be arranged to sandwich the region R1 in the X-axis direction.

[0097] In the third example of the method for manufacturing a radiation detector described above, the support member 12 is attached to the wiring board 7, but the support member 12 may also be attached to the wiring board 4. In other words, the support member 12 may be attached to the wiring board 4 on which the optical semiconductor element 11 is directly mounted, or may be attached to the wiring board 7 on which the optical semiconductor element 11 is indirectly mounted.

[0098] In the above embodiment, the support member 12 is positioned so as to overlap with the plurality of second openings 25b (the plurality of second light receiving sections 20B) when viewed from the Z-axis direction. However, the support member 12 may be positioned so as not to overlap with the plurality of first openings 25a and the plurality of second openings 25b when viewed from the Z-axis direction. For example, the support member 12 may be positioned in a region between the plurality of second openings 25b (the outer edge region R3) and the outer edge of the optical semiconductor element 11 when viewed from the Z-axis direction. In this case, the outer edge region R3 can function as a region for detecting light generated in the scintillator 31. The plurality of second light receiving sections 20B may not be positioned in the outer edge region R3. In this case, the plurality of second openings 25b may not overlap with the plurality of light receiving sections 20. The plurality of second openings 25b may not be provided in the outer edge region R3.

[0099] The radiation detector 1 of the first and second modifications may include another support member, which may be arranged on the optical semiconductor element 11 so as to surround the opening 11a when viewed from the Z-axis direction. The bonding member 13 may not be arranged inside the other support member, and may not be arranged within the opening 11a. In other words, the other support member may function to prevent the bonding member 13 from flowing into the opening 11a. In this case, it is possible to prevent the bonding member 13 from affecting the wire 5 arranged within the opening 11a.

[0100] In the third example of the method for manufacturing a radiation detector described above, the support member 12 is attached to the wiring board 7 after the wiring board 4 on which the optical semiconductor element 11 is mounted is fixed to the wiring board 7. However, the support member 12 may be attached to the wiring board 7 at any timing before the scintillator unit 3 is placed on the support member 12. For example, the support member 12 may be attached to the wiring board 7 before the wiring board 4 is fixed to the wiring board 7.

[0101] 1...radiation detector, 2...photodetector, 3...scintillator unit, 4, 7...wiring board, 5...wire, 6...protective member, 8...mold, 11...optical semiconductor element, 11a...opening (third opening), 12...support member, 12a...support surface, 13...bonding member, 14...semiconductor layer, 14a...surface, 15...first insulating layer, 19...light-receiving region, 20...light-receiving section, 20A...first light-receiving section, 20B...second light-receiving section, 21...APD, 22...quenching resistor, 25...second insulating layer, 25a...first opening, 25b...second opening, 26...bonding film, 31...scintillator, R1...region, R2...effective region, R3...outer edge region, RE...resist, RE1...portion.

Claims

1. An optical semiconductor element including a semiconductor layer that forms a light-receiving region; support members located on one side of the optical semiconductor element in a first direction parallel to the thickness direction of the semiconductor layer and arranged on both sides in a second direction perpendicular to the first direction of a region that overlaps with the light-receiving region when viewed from the first direction; a scintillator unit supported by the support member so as to face the optical semiconductor element across the region in the first direction; and bonding members arranged in the region and in contact with the optical semiconductor element, the support member, and the scintillator unit, respectively; wherein the scintillator unit has a scintillator corresponding to the light-receiving region; the light-receiving region has a plurality of light-receiving sections connected in parallel with each other; and each of the plurality of light-receiving sections includes: an avalanche photodiode operating in Geiger mode; and a quenching element connected in series with the avalanche photodiode; and the refractive index of the scintillator is 1.80 or more and 2.35 or less. A radiation detector, wherein the refractive index of the bonding member is 1.60 or more and 2.00 or less.

2. The radiation detector according to claim 1, wherein the optical semiconductor element further includes a first insulating layer disposed on the semiconductor layer on the side of the region, and the refractive index of the first insulating layer is higher than the refractive index of the bonding member and lower than the refractive index of the semiconductor layer.

3. The radiation detector according to claim 2, wherein the optical semiconductor element further includes a second insulating layer disposed on the first insulating layer on the region side, the second insulating layer covering the quenching element, the second insulating layer having a plurality of first openings opening on both sides in the first direction, each of the plurality of first openings overlapping with a respective one of the plurality of first light receiving sections disposed in the effective region among the plurality of light receiving sections when viewed from the first direction, a portion of the bonding member being disposed in each of the plurality of first openings, and the portion of the bonding member being in contact with the first insulating layer.

4. A radiation detector as described in claim 3, wherein the support member is disposed between the second insulating layer and the scintillator unit, the second insulating layer further has a plurality of second openings that open on both sides in the first direction, and a portion of the support member is disposed in each of the plurality of second openings.

5. A radiation detector as described in claim 4, wherein each of the plurality of second openings overlaps with each of the plurality of second light receiving sections that are arranged outside the effective area among the plurality of light receiving sections when viewed from the first direction.

6. A radiation detector according to claim 5, wherein the plurality of second light receiving sections are arranged in an outer edge region surrounding the effective region when viewed from the first direction.

7. A radiation detector according to any one of claims 1 to 6, further comprising: a wiring board on which a plurality of photodetectors aligned at least in the second direction are mounted; a plurality of wires; and a protective member, wherein each of the plurality of photodetectors includes the optical semiconductor element, the support member arranged between the optical semiconductor element and the scintillator unit, and the joining member, each of the plurality of wires connecting the optical semiconductor element to the wiring board on the outside of the support member in the second direction, and the protective member covering the plurality of wires on the outside of the support member in the second direction.

8. A radiation detector according to any one of claims 1 to 6, further comprising: a wiring board on which the optical semiconductor element is mounted; and a wire connecting the optical semiconductor element and the wiring board, wherein the optical semiconductor element has a third opening that opens on both sides in the first direction, the wire passes through the third opening, and the third opening overlaps the joining member when viewed from the first direction.

9. A radiation detector according to any one of claims 1 to 8, wherein the absolute value of the difference between the refractive index of the scintillator and the refractive index of the joining member is 0.2 or less.

10. A radiation detector as claimed in any one of claims 1 to 9, wherein the semiconductor layer has a surface facing the scintillator unit via the region in the first direction, the support member has a support surface supporting the scintillator unit, and the height from the surface to the support surface in the first direction is 200 μm or less.

11. A photodetector comprising: an optical semiconductor element including a semiconductor layer that constitutes a light-receiving region; and support members that are located on one side of the optical semiconductor element in a first direction parallel to the thickness direction of the semiconductor layer and that are arranged on both sides in a second direction perpendicular to the first direction of a region that overlaps with the light-receiving region when viewed from the first direction, wherein the light-receiving region has a plurality of light-receiving sections connected in parallel with each other, and each of the plurality of light-receiving sections includes an avalanche photodiode that operates in Geiger mode and a quenching element connected in series with the avalanche photodiode.

12. A method for manufacturing a semiconductor device, comprising the steps of: preparing an optical semiconductor element including a semiconductor layer constituting a light-receiving region, a scintillator unit, and a bonding material; arranging support members on both sides in a second direction perpendicular to a first direction of a region that is located on one side of the optical semiconductor element in a first direction parallel to the thickness direction of the semiconductor layer and overlaps with the light-receiving region when viewed from the first direction; arranging the scintillator unit on the support member so as to face the optical semiconductor element across the region in the first direction; and introducing the bonding material into the region so as to contact each of the optical semiconductor element, the support member, and the scintillator unit to form a bonding member, and bonding the optical semiconductor element and the scintillator unit with the bonding member, wherein the scintillator unit has a scintillator corresponding to the light-receiving region, and the light-receiving region has a plurality of light-receiving sections connected in parallel to each other, and each of the plurality of light-receiving sections includes an avalanche photodiode operating in Geiger mode and a quenching element connected in series with the avalanche photodiode, a refractive index of the scintillator being equal to or greater than 1.80 and equal to or less than 2.35, and a refractive index of the bonding member being equal to or greater than 1.60 and equal to or less than 2.

00.

13. A method for manufacturing a radiation detector as described in claim 12, wherein in the step of placing the support member, the support member is formed by applying a resist onto the optical semiconductor element and removing the portion of the resist located in the region.

14. A method for manufacturing a radiation detector as described in claim 12, wherein the step of placing the support member comprises placing a mold on the optical semiconductor element, introducing a resin material into the inside of the mold, and hardening the resin material to form the support member.

15. A method for manufacturing a radiation detector as described in claim 14, further comprising the steps of: preparing a wiring board; mounting the optical semiconductor element on the wiring board; and connecting the optical semiconductor element and the wiring board with a wire; wherein in the step of forming the support member, the resin material is introduced inside the mold so that the resin material covers the wire.

16. A method for manufacturing a radiation detector as described in claim 12, further comprising the steps of: preparing a wiring board; and mounting the optical semiconductor element on the wiring board; wherein in the step of arranging the support member, the support member is attached to the wiring board at positions on both sides of the optical semiconductor element in the second direction.

17. The method for manufacturing a radiation detector according to claim 16, further comprising the step of removing the support member from the wiring board, wherein the step of removing the support member is performed after the step of joining the optical semiconductor element and the scintillator unit.

18. A method for manufacturing a radiation detector, comprising the steps of: preparing an optical semiconductor element including a semiconductor layer that constitutes a light-receiving region, a scintillator unit, and a bonding film; arranging the bonding film in a region that is located on one side of the optical semiconductor element in a first direction parallel to the thickness direction of the semiconductor layer and overlaps with the light-receiving region when viewed from the first direction, and arranging the scintillator unit on the optical semiconductor element so as to face the optical semiconductor element in the first direction across the region; and bonding the optical semiconductor element and the scintillator unit with the bonding film, wherein the scintillator unit has a scintillator that corresponds to the light-receiving region, the light-receiving region has a plurality of light-receiving sections connected in parallel with each other, and each of the plurality of light-receiving sections includes: an avalanche photodiode that operates in Geiger mode; and a quenching element connected in series with the avalanche photodiode, wherein the refractive index of the scintillator is 1.80 or more and 2.35 or less, and the refractive index of the bonding film is 1.60 or more and 2.00 or less.

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