Radiation imaging device and radiation imaging system

Abstract

The aim is to reduce pile-up at subpixels located within pixel boundaries and to accurately measure visible light photons. [Solution] A radiation imaging apparatus having a scintillator section that converts incident radiation into visible light and a photoelectric conversion section that converts the visible light into an electrical signal, wherein the scintillator section is characterized by having a first visible light absorbing member that separates a plurality of scintillators included in the scintillator section in a direction perpendicular to the incident direction of the radiation and a second visible light absorbing member provided on the incident surface of the radiation.

Description

Technical Field

[0001] The present invention relates to a radiation imaging device and a radiation imaging system.

Background Art

[0002] As a radiation imaging apparatus that captures a radiation image using radiation (such as X-rays) transmitted through a subject, an FPD (Flat Panel Detector) capable of displaying a radiation image in real time has been proposed. The FPD arranges minute radiation detectors, each of which is formed by laminating a solid-state photodetector in which an amorphous semiconductor is sandwiched between a transparent conductive film and a conductive film and a scintillator that converts radiation into visible light, in a matrix pattern on a quartz glass substrate. Also, as the solid-state photodetector, those using a photodetector such as a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor) are known. Further, those using a photodetector such as an avalanche photodiode (APD) or a single photon avalanche diode (SPAD) are also known.

[0003] Patent Document 1 discloses an X-ray CT apparatus using an indirect photon counting type sensor. Patent Document 1 also discloses a configuration in which a scintillator is pixel-divided. With this configuration, since visible light generated in the scintillator can be suppressed from entering adjacent pixels, it is disclosed that image quality degradation due to pile-up (the inability to correctly count the number of detections of visible light because the intensity of the visible light incident on a pixel is too high) can be prevented.

[0004] Further, the photodetector described in Patent Document 2 arranges a plurality of sub-pixels in each pixel and detects visible light photons emitted by a scintillator.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in all of the photodetectors described in the patent documents, there was room for improvement in addressing the degradation of image quality due to pile-up. [Means for solving the problem]

[0007] The present invention, which solves the above problems, is a radiation imaging apparatus having a scintillator section that converts incident radiation into visible light and a photoelectric conversion section that converts the visible light into an electrical signal, wherein the scintillator section is characterized by having a first visible light absorbing member that separates a plurality of scintillators included in the scintillator section in a direction perpendicular to the incident direction of the radiation and a second visible light absorbing member provided on the incident surface of the radiation.

[0008] Another invention relates to a radiation imaging apparatus comprising: a scintillator that generates visible light upon irradiation with radiation; a plurality of subpixels each having a photoelectric conversion element that generates an electric charge upon receiving the visible light generated by the scintillator and a sub-signal processing unit that generates an electrical signal upon receiving the electric charge generated by the photoelectric conversion element; and a plurality of pixel pixels each having a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, wherein the visible light receiving area of ​​the photoelectric conversion element differs among the plurality of subpixels.

[0009] Another invention relates to a radiation imaging apparatus comprising: a scintillator that generates visible light upon irradiation with radiation; a plurality of subpixels each having a photoelectric conversion element that generates an electric charge upon receiving the visible light generated by the scintillator and a sub-signal processing unit that generates an electrical signal upon receiving the electric charge generated by the photoelectric conversion element; and a plurality of pixel pixels each having a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, wherein the processing capability of the sub-signal processing unit for processing the electric charge differs among the plurality of subpixels.

[0010] Another invention relates to a radiation imaging apparatus comprising: a scintillator that generates visible light upon irradiation with radiation; a photoelectric conversion unit that generates an electrical signal upon receiving the visible light generated by the scintillator; and a signal processing unit that classifies and outputs the electrical signal generated by the photoelectric conversion unit, wherein the photoelectric conversion unit comprises a plurality of subpixels, each comprising a photoelectric conversion element that generates an electric charge upon receiving the visible light, and a sub-signal processing unit that generates the electrical signal upon receiving the electric charge generated by the photoelectric conversion element, and the plurality of subpixels are arranged such that the visible light detection sensitivity per unit area of ​​the photoelectric conversion unit differs from one another. [Effects of the Invention]

[0011] According to the present invention described above, pile-up in subpixels arranged within a pixel can be reduced, and visible light photons can be measured with high accuracy. [Brief explanation of the drawing]

[0012] [Figure 1] Schematic diagram of the radiation imaging device according to the first embodiment [Figure 2] Cross-sectional view of the radiation imaging device according to the first embodiment [Figure 3] Schematic diagram of the radiation imaging device according to the second embodiment [Figure 4] Cross-sectional view of the radiation imaging device according to the second embodiment. [Figure 5]Schematic configuration diagram of a radiation imaging apparatus according to the third embodiment [Figure 6] Cross-sectional view of a radiation imaging apparatus according to the third embodiment [Figure 7] Schematic diagram of a radiation detection panel according to the fourth embodiment [Figure 8] Schematic diagram of a photoelectric conversion substrate of a radiation detection panel according to the fourth embodiment [Figure 9] Schematic diagram of a signal processing substrate of a radiation detection panel according to the fourth embodiment [Figure 10] Configuration example of a sub-pixel circuit of a radiation detection panel according to the fourth embodiment [Figure 11] Configuration example of a pixel circuit of a radiation detection panel according to the fourth embodiment [Figure 12] Schematic diagram showing the driving of a pixel circuit of a radiation detection panel according to the fourth embodiment [Figure 13] Configuration example of a photoelectric conversion substrate of a radiation detection panel according to the fourth embodiment [Figure 14] Plan view of a radiation detection panel according to the fourth embodiment [Figure 15] Cross-sectional view in the diagonal direction of a radiation detection panel according to the fourth embodiment [Figure 16] Cross-sectional view of a radiation detection panel according to the fourth embodiment [Figure 17] Cross-sectional view of a conventional radiation detection panel [Figure 18] Cross-sectional view of a radiation detection panel of Example 1 of the fourth embodiment [Figure 19] Cross-sectional view of a radiation detection panel of Example 2 of the fourth embodiment [Figure 20] Cross-sectional view of a radiation detection panel of Example 3 of the fourth embodiment [Figure 21] Cross-sectional view of a radiation detection panel of Example 4 of the fourth embodiment [Figure 22] Configuration example of a radiation imaging system of the present disclosure [Figure 23] Partial top view of a radiation detection panel of Example 1 of the fourth embodiment [Figure 24] Partial top view of a radiation detection panel of Example 2 of the fourth embodiment [Figure 25] Schematic diagram illustrating an example of the application of the radiographic imaging device of this disclosure to an X-ray diagnostic system. [Modes for carrying out the invention]

[0013] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0014] In the following description, terms indicating specific directions or positions (e.g., "up," "down," "right," "left," and other terms including these) will be used as needed. The use of these terms is for the purpose of facilitating the understanding of embodiments with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention.

[0015] In this specification, a plan view refers to viewing a semiconductor layer from a direction perpendicular to the light incident surface. A cross-sectional view refers to a surface perpendicular to the light incident surface of the semiconductor layer. If the light incident surface of the semiconductor layer is rough when viewed microscopically, the plan view is defined based on the light incident surface of the semiconductor layer as viewed macroscopically.

[0016] The semiconductor layer has a first surface and a second surface opposite to the first surface, to which light is incident. In this specification, the depth direction is the direction from the first surface to the second surface of the semiconductor layer in which the APD is placed. Hereafter, the "first surface" may be referred to as the "front surface" and the "second surface" may be referred to as the "back surface".

[0017] In the following description, the anode of the avalanche photodiode (APD) is set to a fixed potential, and the signal is taken from the cathode side. Therefore, the semiconductor region of the first conductivity type, which has majority carriers of the same polarity as the signal charge, is an N-type semiconductor region, and the semiconductor region of the second conductivity type, which has majority carriers of charges with a different polarity than the signal charge, is a P-type semiconductor region. Note that the present invention also applies when the cathode of the APD is set to a fixed potential and the signal is taken from the anode side. In this case, the semiconductor region of the first conductivity type, which has majority carriers of the same polarity as the signal charge, is a P-type semiconductor region, and the semiconductor region of the second conductivity type, which has majority carriers of charges with a different polarity than the signal charge, is an N-type semiconductor region. The following description will focus on the case where one node of the APD is set to a fixed potential, but the potentials of both nodes may fluctuate.

[0018] In this specification, when the term "impurity concentration" is used, it refers to the net impurity concentration after subtracting the amount compensated by reverse-conductivity impurities. The region where the concentration of P-type added impurities is higher than that of N-type added impurities is the P-type semiconductor region. Conversely, the region where the concentration of N-type added impurities is higher than that of P-type added impurities is the N-type semiconductor region.

[0019] Figure 22 shows an example of the basic configuration of a radiation imaging system 980 according to an embodiment of the present invention. The radiation imaging system 980 is configured to generate an electrical radiation image by electrically capturing an optical image formed by radiation. The radiation is typically X-rays, but may also be alpha rays, beta rays, gamma rays, etc. The radiation imaging system 980 includes, for example, a radiation imaging device 990 and a control device 983 consisting of a computer that acquires image data from the radiation imaging device 990 and processes the acquired image data. In this embodiment, a preferred configuration further includes a display 982, an exposure control device 981, and a radiation generator 984.

[0020] The radiation generator 984 begins irradiating with radiation 985 in accordance with the exposure command (radiation command) from the exposure control device 981. The radiation 985 emitted from the radiation generator 984 passes through the subject 986 and enters the radiation imaging device 990. The radiation generator 984 also stops irradiating with radiation 985 in accordance with the stop command from the exposure control device 981.

[0021] The radiation imaging device 990 includes a radiation detection panel 991, a control circuit 993, and an image generation circuit 992. The radiation detection panel 991 generates a radiation image corresponding to the radiation 985 incident on the radiation imaging device 990 and transmits it to the computer 983. The control circuit 993 controls the operation of the radiation detection panel 991. For example, based on the image signal obtained from the radiation detection panel 991, the control circuit 993 generates a stop signal to stop the irradiation of radiation 985 from the radiation generator 984. The stop signal is supplied to the exposure control device 981. In response to the stop signal, the exposure control device 981 sends a stop command to the radiation generator 984.

[0022] The control circuit 993 may be composed of a dedicated circuit such as a PLD (Programmable Logic Device) like an FPGA (Field Programmable Gate Array), or a dedicated circuit such as an ASIC (Application Specific Integrated Circuit). Alternatively, the control circuit 993 may be composed of a combination of a general-purpose processing circuit such as a processor and a memory circuit such as memory. In this case, the functions of the control circuit 993 may be realized by the general-purpose processing circuit executing a program stored in the memory circuit.

[0023] The image generation circuit 992 stores the signal supplied from the radiation detection panel 991 in memory and generates a radiation image based on this signal. Details of the radiation image generation method will be described later. The image generation circuit 992 transmits the generated radiation image to the computer 983.

[0024] The computer 983 includes a control unit that controls the radiation imaging device 990 and the exposure control device 981, a receiving unit that receives radiation images from the radiation imaging device 990, and a signal processing unit that processes the radiation images obtained by the radiation imaging device 990. The control unit, receiving unit, and signal processing unit may each be configured by dedicated circuits, similar to the control circuit 993, or by a combination of general-purpose processing circuits and memory circuits. In one example, the exposure control device 981 has an exposure switch, and when the exposure switch is turned on by the user, it sends an exposure command to the radiation generator 984 and a start notification to the computer 983 indicating the start of radiation irradiation. Upon receiving the start notification, the computer 983 responds to the start notification by notifying the control circuit 993 of the radiation imaging device 990 of the start of radiation irradiation. If the exposure control device 981 and the computer 983 are not synchronously connected, the radiation detection panel 991 may detect the start of radiation irradiation of radiation 985 based on the pixel signal.

[0025] [First Embodiment] A schematic configuration example of a radiation imaging apparatus according to the first embodiment of this disclosure will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram of the radiation imaging apparatus, and Figure 2 is a cross-sectional view.

[0026] As shown in Figures 1 and 2, the radiation detection panel 1100 (radiation detection panel 991 in Figure 22) comprises a scintillator section 1200 and a photoelectric conversion section 1300. The scintillator section 1200 is also referred to as the scintillator panel. X-ray photons 1400 are incident on the scintillator section 1200 and are converted and multiplied into visible light photons 1500 by the scintillator section 1200. The surface on which the X-ray photons 1400 are incident on the scintillator section 1200 is also referred to as the radiation incident surface. The visible light photons 1500 are incident on the photoelectric conversion section 1300 and detected as an electrical signal. The photoelectric conversion section 1300 comprises a photoelectric conversion substrate (hereinafter sometimes referred to as a photodiode substrate) 1310 and a signal processing substrate (hereinafter sometimes referred to as a counter circuit board) 1320.

[0027] The photodiode substrate 1310 and the counter circuit board 1320 are stacked and electrically connected. The photodiode substrate 1310 has a pixel region in which pixels 1301, which have sensor functions, are arranged in a matrix. Therefore, the photodiode substrate 1310 may also be called a sensor component, sensor substrate, or sensor chip. The counter circuit board 1320 has a circuit region for processing signals detected in the pixel region. The counter circuit board 1320 may also be called a circuit component, circuit board, or circuit chip. Both substrates are semiconductor substrates made of silicon wafer material.

[0028] The photodiode substrate 1310 has a first semiconductor layer 1311 and a first wiring structure 1312 for forming a photodiode, which is a photoelectric conversion element, and these constitute the pixel 1301. As described later, the scintillator portion 1200 of this embodiment has a small amount of light emitted, so an avalanche photodiode, which has the function of amplifying signals, is preferred as the photoelectric conversion element. The counter circuit substrate 1320 has a second semiconductor layer 1321 and a second wiring structure 1322 that constitute a circuit such as a signal processing unit, corresponding to the pixel 1301.

[0029] The photoelectric conversion unit 1300 is a back-illuminated type photoelectric conversion unit. That is, visible light photons 1500 are incident from a second surface facing the first surface on which the first wiring structure 1312 of the photodiode substrate 1310 is formed, and the counter circuit board 1320 is arranged on the first surface side of the photodiode substrate 1310. Note that the invention according to each embodiment can also be applied to a photoelectric conversion unit having a front-illuminated structure.

[0030] The scintillator section 1200 and the photoelectric conversion section 1300 are arranged on top of each other via an adhesive member 1201, as shown in Figure 2. The adhesive member 1201 can be an adhesive member that has the property of melting or softening when heated. The adhesive member 1201 can be a sheet-like or liquid adhesive material (also called a hot-melt resin) containing thermoplastic elastomers such as styrene-based, olefin-based, PVC-based, urethane-based, or amide-based materials. Alternatively, the adhesive member 1201 can be an adhesive sheet such as an acrylic-based or silicone-based adhesive sheet that has adhesive properties at room temperature.

[0031] The scintillator section 1200 has multiple scintillators 1210 separated by partitions (sometimes referred to as separation regions) 1220. The multiple scintillators 1210 are separated in a direction perpendicular to the direction of radiation incidence (the direction of incidence of X-ray photons 1400). A support substrate 1230 is also positioned on the X-ray incidence side of the scintillator section 1200. Both the separation region (partition) 1220 and the support substrate 1230 are visible light absorbing members that have light absorption functions. The partition (partition) 1220 and the support substrate 1230 can suppress the spreading of visible light photons generated in the scintillators 1210. Furthermore, the partition (partition) 1220 and the support substrate 1230 can reduce the amount of visible light photons generated in the scintillators 1210. Furthermore, by adjusting the size of the partition wall (separation region) 1220, the amount (volume) of the scintillator 1210 can be adjusted, thereby allowing adjustment of the amount of visible light photons generated by the scintillator 1210. The visible light absorbing member used as the partition wall (separation region) 1220 is an example of the first visible light absorbing member. The visible light absorbing member used as the support substrate 1230 is an example of the second visible light absorbing member.

[0032] An example of a manufacturing method for the scintillator section 1200 will be described. First, a support substrate 1230 is prepared, such as glass, amorphous carbon, CFRP, resin film, aluminum, or titanium. A photosensitive polyimide resin is applied to this, and a separation region (separation wall) 1220 is formed using photolithography technology. Furthermore, a black resin or metal film is formed on the surface of the separation wall (separation region) 1220. After that, particulate Gd2O2S (GOS), which is the scintillator 1210, is filled into the compartment formed by the separation wall (separation region) 1220.

[0033] As mentioned above, pile-up can occur if the amount of visible light photons 1500 generated in the scintillator 1210 exceeds the processing capacity of the photoelectric conversion unit 1300, or if the visible light photons 1500 are diffused in the scintillator unit 1200. Improvement is particularly necessary in FPDs, which require a large area and high image sharpness.

[0034] In this embodiment, the scintillator 1210 of the radiation imaging apparatus is separated by a partition (separation region) 1220 having a light-absorbing function and a support substrate 1230. This suppresses the diffusion of light to adjacent pixels and reduces the amount of light generated. Furthermore, by increasing the size of the partition (separation region) 1220, the amount (volume) of phosphor can be reduced, thereby reducing the amount of visible light photons generated by the scintillator 1210. As a result, the amount of light incident on the photoelectric conversion unit 1300 can be reduced, thus suppressing pile-up. Moreover, since photolithography technology is used in the formation of the separation region 1220, it is easy to increase the area, and manufacturing costs can be reduced.

[0035] As described above, the radiation imaging apparatus of this disclosure can provide a high-quality radiation imaging apparatus that can reduce pile-up by arranging a visible light absorbing member on the side to which radiation is incident on the photoelectric conversion unit 1300.

[0036] [Second Embodiment] A schematic configuration example of a radiation imaging apparatus according to the second embodiment of this disclosure will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram of the radiation imaging apparatus, and Figure 4 is a cross-sectional view. The operating principle of the radiation imaging apparatus is the same as that of the first embodiment, so a description will be omitted. The differences from the first embodiment will be described in detail below.

[0037] As shown in Figures 3 and 4, the radiation detection panel 1100 comprises a scintillator section 1200 and a photoelectric conversion section 1300. The photoelectric conversion section 1300 is composed of a single photoelectric conversion substrate 1330, which has semiconductor layers on the same substrate that constitute the photoelectric conversion element and circuits such as the signal processing section. That is, the pixel 1302 has a first semiconductor layer 1311, a first wiring structure 1312, a second semiconductor layer 1321, and a second wiring structure 1322. Since one pixel is formed by the photoelectric conversion element and the signal processing circuit, the area of ​​the photoelectric conversion element in this embodiment is smaller than that of the photoelectric conversion element in the first embodiment. For this reason, an avalanche photodiode having the function of amplifying signals is suitable for the photoelectric conversion element.

[0038] In Figure 4, each semiconductor layer is arranged to correspond to the separated scintillator 1210. However, the second semiconductor layer 1321, which does not contribute to photoelectric conversion, does not necessarily need to be placed within the section of the scintillator 1210; for example, it may overlap with the separation region (partition) 1220. Furthermore, the scintillator section 1200 and the photoelectric conversion section 1300 may be offset and overlapped so that the second semiconductor layer 1321 corresponds to the adjacent section.

[0039] An example of a manufacturing method for the scintillator section 1200 will be described. First, a partition wall (separation region) 1220, such as glass or silicon, is prepared. A photosensitive photoresist, for example, is applied to this, and a mask pattern is formed using photolithography technology. Next, unnecessary parts are removed using dry etching technology, and the photoresist is further peeled off to form the partition wall (separation region) 1220. After that, the powdered CsI:Tl raw material for the scintillator 1210 is melted and filled into the compartment formed by the partition wall (separation region) 1220. From the viewpoint of light absorption and processability, a silicon wafer is preferable as the material for the partition wall (separation region) 1220, which is a visible light absorbing member. Furthermore, by using silicon, which is the same material as the semiconductor substrate constituting the photoelectric conversion section 1300, when bonding the scintillator section 1200 and the photoelectric conversion section 1300, misalignment due to thermal expansion can be suppressed.

[0040] As mentioned above, pile-up is a significant challenge in photon-counting type FPDs.

[0041] In this embodiment, the scintillator 1210 of the radiation imaging apparatus is separated by a partition (separation region) 1220 having a light-absorbing function, and therefore, similar to the scintillator 1210 of the first embodiment, it is possible to suppress the diffusion of light to adjacent pixels. Furthermore, it is possible to reduce the amount of light generated. That is, by reducing the amount of light incident on the photoelectric conversion section, the occurrence of pile-up can be suppressed. In addition, since photolithography technology is used in the formation of the partition (separation region) 1220, it is easy to increase the area and reduce manufacturing costs.

[0042] Furthermore, the support substrate 1230 and the partition wall (separation region) 1220 may be integrally formed from the same material (for example, silicon, which is a visible light absorbing material). By integrally forming the support substrate 1230 and the partition wall (separation region) 220 from silicon, there is an effect of eliminating the need for a support substrate 1230 made of, for example, glass.

[0043] As described above, the radiation imaging apparatus of this disclosure can provide a high-quality radiation imaging apparatus that can reduce pile-up by arranging a visible light absorbing member on the side to which radiation is incident on the photoelectric conversion unit 1300.

[0044] [Third Embodiment] A schematic configuration example of a radiation imaging apparatus according to the third embodiment of this disclosure will be described with reference to Figures 5 and 6. Figure 5 is a schematic diagram of the radiation imaging apparatus, and Figure 6 is a cross-sectional view. The operating principle of the radiation imaging apparatus is the same as that of the first embodiment, so a description will be omitted. The differences from the above embodiment will be described in detail below.

[0045] As shown in Figures 5 and 6, the radiation detection panel 1100 comprises a scintillator section 1200, a photoelectric conversion section 1300, and a visible light absorbing section 1600. The photoelectric conversion section 1300 and the visible light absorbing section 1600 are joined by an adhesive member 1601. The photoelectric conversion section 1300 is composed of a photoelectric conversion substrate 1330 in which a semiconductor layer having a photoelectric conversion element and a circuit such as a signal processing unit is formed on the same substrate, similar to the second embodiment. The visible light absorbing member used in the visible light absorbing section 1600 is an example of a third visible light absorbing member.

[0046] As mentioned above, pile-up is a significant challenge in photon-counting type FPDs.

[0047] Since the scintillator 1210 has the same structure as in the second embodiment, it is possible to reduce manufacturing costs and pile-up in the radiation imaging device of this embodiment as well.

[0048] In this embodiment, a visible light absorbing section 1600 is further arranged between the scintillator section 1200 and the photoelectric conversion section 1300. The visible light absorbing section 1600 is preferably made of a material that prioritizes the straight-line propagation of visible light, such as an FOP (Fiber Optic Plate). The FOP has the function of reflecting obliquely incident light by controlling the refractive index of the material, thereby suppressing the incidence of visible light into the FOP. In addition, by arranging light absorbing members at predetermined intervals within the FOP, it has the function of absorbing oblique light within the FOP. By using such a visible light absorbing member as an FOP, the amount of visible light incident on the photoelectric conversion substrate can be reduced, thereby suppressing the occurrence of pile-up.

[0049] Furthermore, in the photoelectric conversion unit 1300, a light intensity adjustment layer 1313 is positioned on the X-ray incident side of the first semiconductor layer 1311 that forms the avalanche photodiode. The light intensity adjustment layer 1313 is formed in a position that reduces the visible light incident on the avalanche photodiode. That is, the light intensity adjustment layer 1313 can act as a light-shielding pattern to reduce the light incident on the avalanche photodiode, which is a photoelectric conversion element. The light intensity adjustment layer 1313, which is a visible light adjustment member, is preferably made of a material that can absorb visible light, such as a metal film or a black organic film. The light transmitted through the FOP, which is a visible light absorption unit 1600, has its light intensity further reduced by this light intensity adjustment layer 1313, and the remaining light is incident on the first semiconductor layer 1311. This makes it possible to suppress the occurrence of pile-up. It is desirable that the aperture area of ​​the light intensity adjustment layer 1313 be adjusted according to the processing capacity of the photoelectric conversion unit 1300. The visible light adjusting member used as the light intensity adjusting layer 1313 is an example of a fourth visible light absorbing member.

[0050] As described above, the radiation imaging apparatus of this disclosure can provide a high-quality radiation imaging apparatus that can reduce pile-up by arranging a visible light absorbing member on the side to which radiation is incident on the photoelectric conversion unit 1300.

[0051] Next, a fourth embodiment of the present invention will be described along with several examples. First, the configuration common to each embodiment of this invention will be described using Figures 7 to 18.

[0052] Figure 7 shows the configuration of a radiation detection panel 991 in which a scintillator section 500 is further stacked on a stacked photoelectric conversion section 100. Radiation photons 600 are incident on the scintillator section 500, and the scintillator section 500 converts and multiplies the radiation photons 600 into visible light photons 700. Generally, the scintillator section 500 multiplies one radiation photon 600 by approximately 1000 times, and emits thousands of visible light photons.

[0053] The amplified visible light photons 700 are incident on the photoelectric conversion unit 100 and detected as electrical signals in the photoelectric conversion unit 100.

[0054] The photoelectric conversion unit 100 is constructed by stacking and electrically connecting two components: a photoelectric conversion substrate (corresponding to the photodiode substrate in Embodiments 1 to 3) 11 and a signal processing substrate (corresponding to the counter circuit substrate in Embodiments 1 to 3) 21. The photoelectric conversion substrate 11 has a first semiconductor layer having a photoelectric conversion element 102 (described later) and a first wiring structure. The signal processing substrate 21 has a second semiconductor layer having a circuit such as a signal processing unit 103 (described later) and a second wiring structure. The photoelectric conversion unit 100 is constructed by stacking the second semiconductor layer, the second wiring structure, the first wiring structure, and the first semiconductor layer in that order. The photoelectric conversion unit 100 is a back-illuminated type photoelectric conversion unit in which visible light photons 700 are incident from the second surface and the signal processing substrate 21 is located on the first surface side. The inventions according to each embodiment and example can also be applied to a photoelectric conversion unit having a front-illuminated structure, and can also be applied to a photoelectric conversion unit consisting of a single layer instead of a stacked type.

[0055] Figure 8 shows an example of the arrangement of the photoelectric conversion substrate 11. Pixel pixels 901 (corresponding to pixels 1301 in the first to third embodiments), each containing a photoelectric conversion element 102 including an avalanche photodiode (APD), are arranged in a 5x5 grid, forming a two-dimensional array in plan view. This two-dimensional array of pixels 901 forms a pixel region 12. Here, the left-right direction in Figure 8 is referred to as the "row direction," "horizontal direction," or "x direction," and the up-down direction in Figure 8 is referred to as the "column direction," "vertical direction," or "y direction." The direction perpendicular to the plane of the paper in Figure 8 is referred to as the "depth direction," or "z direction." A pixel 901 constitutes one pixel, the smallest unit used to generate a radiation image, and may be simply referred to as a pixel 901 in the following explanation. A subpixel 101 is a single divided region obtained by dividing a pixel 901 into multiple parts.

[0056] Figure 9 is a diagram showing the configuration of the signal processing board 21. It has a sub-signal processing unit 103 that processes the charge photoelectrically converted by the photoelectric conversion element 102 in Figure 8, and a signal processing unit 902 that combines the signals from the sub-signal processing unit 103 into signals for each pixel. It also has a readout circuit 112, a control pulse generation unit 115, a horizontal scanning circuit unit 111, signal lines 113, a vertical scanning circuit unit 110, and drive lines 116.

[0057] The photoelectric conversion element 102 in Figure 8 and the sub-signal processing unit 103 in Figure 9 are electrically connected via connection wiring provided for each subpixel.

[0058] The vertical scanning circuit section 110 receives control pulses supplied from the control pulse generation section 115 and supplies control pulses to each pixel via the drive line 116. Logic circuits such as a shift register and an address decoder are used in the vertical scanning circuit section 110.

[0059] The signal output from the subpixel photoelectric conversion element 102 is processed by the sub-signal processing unit 103.

[0060] The sub-signal processing unit 103 is equipped with a counter and memory, and the memory stores the visible light photon count value. The visible light photon count value is reset once each time a radiation photon is detected.

[0061] The signal processing unit 902 reads the visible light photon count values ​​from the 5x5 sub-signal processing unit 103, integrates them, and estimates the energy of the radiation photon 600. For example, if the sum of the 5x5 visible light photon count values ​​is 100 counts, it recognizes that 40kV radiation photon 600 has been irradiated, and adds 1 count to the 30kV-60kV radiation photon count value. If the sum of the 5x5 visible light photon count values ​​is 200 counts, it identifies that 80kV radiation photons have been irradiated, and adds 1 count to the 60-90kV radiation photon count value. The visible light photon count values ​​vary depending on the configuration of the scintillator and reflective layer, so they are not limited to 100 counts or 200 counts.

[0062] The horizontal scanning circuit unit 111 inputs control pulses to the signal processing unit 902 to sequentially select each column in order to read a signal from the memory of each pixel in which the radiation photon count value is stored.

[0063] For the selected column, a signal is output from the signal processing unit 902 of the pixel selected by the vertical scanning circuit unit 110 to the signal line 113.

[0064] The signal output to signal line 113 is output via output circuit 114 to an external recording unit or image generation circuit 992 of the photoelectric conversion unit 100. Therefore, the generated image is a digital value obtained by estimating and counting the energy of radiation photons from the visible light photon count values ​​output from multiple subpixels. For example, if the output value of one pixel is divided into three categories: 30-60kV radiation photons, 60-90kV radiation photons, and 90-120kV radiation photons, and each is represented by an 8-bit counter, then one pixel will consist of a 24-bit digital value.

[0065] In Figure 8, the arrangement of photoelectric conversion elements 102 in the pixel region may be one-dimensional. The signal processing unit does not necessarily need to be provided for each photoelectric conversion element; for example, a single signal processing unit may be shared by multiple photoelectric conversion elements 102, and signal processing may be performed sequentially.

[0066] As shown in Figures 8 and 9, multiple signal processing units 902 are arranged in the region that overlaps with the pixel region 12 in a plan view. Then, the vertical scanning circuit unit 110, the horizontal scanning circuit unit 111, the readout circuit 112, the output circuit 114, and the control pulse generation unit 115 are arranged so as to overlap between the edge of the photoelectric conversion substrate 11 and the edge of the pixel region 12 in a plan view. In other words, the photoelectric conversion substrate 11 has a pixel region 12 and a non-pixel region arranged around the pixel region 12. Then, the vertical scanning circuit unit 110, the horizontal scanning circuit unit 111, the readout circuit 112, the output circuit 114, and the control pulse generation unit 115 are arranged in the region that overlaps with the non-pixel region in a plan view.

[0067] Furthermore, the vertical scanning circuit section 110, the horizontal scanning circuit section 111, the readout circuit 112, the output circuit 114, and the control pulse generation section 115 may be arranged within the pixel area 12. In that case, the photoelectric conversion substrate 11 and the signal processing substrate 21 can be tiled in the x and y directions to increase the area.

[0068] Furthermore, multiple photoelectric conversion boards 11 and signal processing boards 21 can be stacked in the z-direction on a single wiring board to increase the surface area.

[0069] Figure 10 is an example of a block diagram including the equivalent circuits of Figures 8 and 9. In Figure 10, the photoelectric conversion element 102 having the APD201 is provided on the photoelectric conversion substrate 11, and the other components are provided on the signal processing substrate 21.

[0070] The APD201 generates charge pairs corresponding to incident light through photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD201. In addition, a voltage VH (second voltage), which is higher than the voltage VL supplied to the anode, is supplied to the cathode of the APD201. A reverse bias voltage is supplied to the anode and cathode such that the APD201 performs avalanche multiplication. By supplying these voltages, the charge generated by the incident light undergoes avalanche multiplication, and an avalanche current is generated.

[0071] Furthermore, when a reverse bias voltage is supplied, there are two modes of operation: Geiger mode, in which the potential difference between the anode and cathode is greater than the breakdown voltage, and linear mode, in which the potential difference between the anode and cathode is near or below the breakdown voltage.

[0072] An APD operating in Geiger mode is called a single-photon avalanche diode (SPAD). For example, the voltage VL (first voltage) is -30V and the voltage VH (second voltage) is 1V. The APD201 may operate in linear mode or Geiger mode. In the case of a SPAD, the potential difference is larger compared to a linear-mode APD, and the effect of voltage withstand capability is more pronounced, so it is preferable to use a SPAD.

[0073] The quench element 202 is connected to the power supply that provides voltage VH and to the APD201. The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, suppressing the voltage supplied to the APD201 and thereby suppressing avalanche multiplication (quench operation). The quench element 202 also works to restore the voltage supplied to the APD201 to voltage VH by flowing the current that compensates for the voltage drop caused by the quench operation (recharge operation). In this explanation, a passive type quench element has been described, but an active type quench element (MOS transistor) may also be used, and the recharge operation may be performed by inputting a clock pulse.

[0074] The sub-signal processing unit 103 includes a waveform shaping unit 210 and a counter circuit 211. In this specification, the sub-signal processing unit 103 may include either the waveform shaping unit 210 or the counter circuit 211.

[0075] The waveform shaping unit 210 shapes the cathode potential change of the APD201 obtained during photon detection and outputs a pulse signal. For example, an inverter circuit can be used as the waveform shaping unit 210. Figure 10 shows an example in which one inverter is used as the waveform shaping unit 210, but a circuit in which multiple inverters are connected in series may be used, or other circuits that have a waveform shaping effect may be used.

[0076] The counter circuit 211 counts the pulse signals output from the waveform shaping unit 210 and stores the visible light photon count value. When the control pulse pRES is supplied, the signal held in the counter circuit 211 is reset.

[0077] A switch such as a transistor may be placed between the quench element 202 and the APD201, or between the photoelectric conversion element 102 and the sub-signal processing unit 103, to switch the electrical connection. Similarly, the supply of voltage VH or voltage VL to the photoelectric conversion element 102 may be electrically switched using a switch such as a transistor.

[0078] In this embodiment, a configuration using a counter circuit 211 is shown. However, instead of the counter circuit 211, a photoelectric conversion unit 100 may be used to acquire pulse detection timing using a time-to-digital converter (TDC) and memory. In this case, the generation timing of the pulse signal output from the waveform shaping unit 210 is converted into a digital signal by the TDC. A control pulse pREF (reference signal) is supplied to the TDC from the vertical scanning circuit unit 110 in Figure 9 via the drive line 214 to measure the timing of the pulse signal. The TDC uses the control pulse pREF as a reference and acquires the signal as a digital signal when the input timing of the signal output from each pixel via the waveform shaping unit 210 is considered as a relative time.

[0079] Figure 11 is an example of a block diagram including the equivalent circuit of the signal processing unit 902. The sub-signal processing units 103 shown in Figure 10 are arranged in a 5x5 grid, and the visible light photon count values ​​held in the counter circuits 211 of each sub-signal processing unit 103 are added together in the integration unit 903. The comparison unit 904 compares the integrated visible light photon count values ​​with a threshold. It then classifies the data into one of the following: 30kV~60kV radiation photon counter 905, 60kV~90kV radiation photon counter 906, or 90kV~120kV radiation photon counter 907. The counter is then incremented according to the energy of the radiation photons. After one frame of imaging has elapsed, a control pulse pSEL is supplied from the vertical scanning circuit unit 110 in Figure 9 via the drive line 214 in Figure 10. Then, the electrical connection and disconnection between the 30kV-60kV radiation photon counter 905, the 60kV-90kV radiation photon counter 906, the 90kV-120kV radiation photon counter 907 and the signal line 113 are switched. Then, the count value is read out. The selection circuit 212 includes, for example, a buffer circuit for outputting the signal.

[0080] Figures 12A and 12B schematically illustrate the relationship between the operation of the APD and the output signal. Figure 12A is an excerpt of the APD 201, quench element 202, and waveform shaping unit 210 from Figure 10. Here, the input side of the waveform shaping unit 210 is denoted as nodeA, and the output side as nodeB. The upper part of Figure 12B shows the waveform change at nodeA, and the lower part shows the waveform change at nodeB.

[0081] Between time t0 and time t1, a potential difference of VH-VL is applied to APD201. When a photon is incident on APD201 at time t1, avalanche multiplication occurs in APD201, an avalanche multiplication current flows through the quench element 202, and the voltage at nodeA drops. As the voltage drop increases further and the potential difference applied to APD201 decreases, the avalanche multiplication of APD201 stops as at time t2, and the voltage level at nodeA stops dropping below a certain value. Subsequently, between time t2 and time t3, a current flows through nodeA to compensate for the voltage drop from voltage VL, and at time t3, nodeA settles to its original potential level. At this time, any portion of the output waveform at nodeA that exceeds a certain threshold is waveform-shaped by the waveform shaping unit 210 and output as a signal at nodeB.

[0082] Figure 13 is an equivalent circuit diagram when the sub-signal processing unit 103 shown in Figure 9 is not used.

[0083] In Figure 9, a sub-signal processing unit 103 is provided for each sub-pixel 101. In contrast, in the equivalent circuit diagram shown in Figure 13, the anodes and cathodes of the APD201 of the sub-pixels arranged in a 5x5 grid are all connected, and the quench elements 202 connected to the cathodes are combined into one at pixel 901. Therefore, the number of connections between the photoelectric conversion substrate 11 and the signal processing substrate 21 can be reduced, and there is no need to provide a sub-signal processing unit 103. In the configuration shown in Figure 13, the energy of the radiation photon can be identified from the pulse height value appearing at nodeC.

[0084] Figures 14 and 15 show the structure of the photoelectric conversion substrate 11 (sensor substrate) of the photoelectric conversion unit. Figure 14 is a plan view showing the configuration of the pixel region, schematically showing the semiconductor layer 300 of the photoelectric conversion substrate 11 as viewed from the first surface. Figure 15 is a cross-sectional view along line AA (diagonal direction) of Figure 14.

[0085] As shown in Figure 14, multiple APD201s are arranged in a two-dimensional array in the semiconductor layer 300, in the row direction (left-right direction in Figure 14) and column direction (up-down direction in Figure 14). In Figure 14, for illustrative purposes only, only nine APD201s in a 3x3 arrangement are depicted, but in an actual product, for example, hundreds of thousands to millions of APD201s are formed. Each APD201 corresponds to one pixel.

[0086] The semiconductor layer 300 is provided with isolation sections 330, which are isolation structures for reducing crosstalk between adjacent APDs 201, 201. The isolation sections 330 are formed in a grid pattern by a plurality of row-direction isolation sections 330X extending in the row direction and a plurality of column-direction isolation sections 330Y extending in the column direction. An APD 201 is placed in each of the sections divided by this grid-like isolation section 330. In this embodiment, the section corresponding to one pixel has a substantially square shape in plan view. The boundaries of the sections are provided so as to overlap, for example, the isolation sections 330. The cathode wiring contact plugs 326 formed in the wiring structure 320 are placed substantially in the center of the pixel (section), and the anode wiring contact plugs 324 are placed at the four corners of the pixel. That is, in this embodiment, four anode contact plugs 324 are provided for one pixel.

[0087] As shown in Figure 15, the photoelectric conversion substrate 11 (sensor substrate) has a structure in which a semiconductor layer 300 and a wiring structure 320 are stacked. The side of the semiconductor layer 300 facing the wiring structure 320 is called the first surface, and the side opposite the first surface is called the second surface. The semiconductor layer 300 is made of silicon, for example. On the second surface of the semiconductor layer 300, a fixed charge film 310, an insulating film 311, a planarization film 312, etc., are stacked in order, and a microlens 313 corresponding to each pixel is provided above them. In other words, the photoelectric conversion unit of this embodiment has a so-called back-illuminated structure in which light is incident on the semiconductor layer 300 from the second surface side. The second surface is sometimes called the light incident surface. Although a microlens 313 is provided in Figure 15, it is not necessarily required. Furthermore, the following structure can be applied to the light incident surface. For example, at least one recess or protrusion can be arranged on the second surface, which is the light incident surface. The uneven structure can be made of silicon, which constitutes the semiconductor layer 300, and other materials. For example, an insulator such as a silicon oxide film, a silicon oxynitride film, or a silicon nitride film is placed in a recess provided in the semiconductor layer 300. An interface with a refractive index difference that is not parallel to the second surface is formed. With this configuration, the incident light is diffracted, which can improve sensitivity to light in the infrared region.

[0088] The fixed charge film 310 is made of a dielectric material having a negative fixed charge and is arranged across the entire second surface of the semiconductor layer 300. The material of the fixed charge film 310 can be selected from, for example, hafnium oxide, aluminum oxide, zirconium oxide, titanium oxide, tantalum oxide, and ruthenium oxide, with aluminum oxide or hafnium oxide being preferred. The fixed charge film 310 may consist of multiple layers. The insulating film 311 is arranged on the fixed charge film 310 across the entire second surface. The insulating film 311 can preferably be, for example, a silicon oxide film, a silicon oxynitride film, or a silicon nitride film. The insulating film 311 may also consist of multiple layers. Although not shown in the figures, in addition to the planarization film 312, a filter layer such as a color filter or an infrared light cut filter may be provided on the second surface side of the semiconductor layer 300.

[0089] The wiring structure 320 is a structure in which multiple layers of wiring 321, 322, 323, via plugs 325, 327 for connecting the wirings, anode wiring contact plug 324, cathode wiring contact plug 326, etc. are arranged within the insulating layer 329. The lower surface of the wiring structure 320 (opposite the semiconductor layer 300) is the bonding surface with the signal processing substrate 21, and multiple bonding portions 328 are provided on the bonding surface.

[0090] The semiconductor layer 300 has a first semiconductor region 301, a second semiconductor region 302, a third semiconductor region 303, a fourth semiconductor region 304, a fifth semiconductor region 305, a sixth semiconductor region 306, a seventh semiconductor region 307, an eighth semiconductor region 308, and a ninth semiconductor region 309. Each semiconductor region is a region to which impurities have been added by ion implantation, or a region to which impurities have been added during the fabrication and epitaxial growth of the semiconductor substrate. Here, the first semiconductor region 301, the sixth semiconductor region 306, the seventh semiconductor region 307, and the eighth semiconductor region 308 are semiconductor regions of the first conductivity type (N-type in this embodiment). The second semiconductor region 302, the third semiconductor region 303, the fourth semiconductor region 304, the fifth semiconductor region 305, and the ninth semiconductor region 309 are semiconductor regions of the second conductivity type (P-type in this embodiment).

[0091] The first semiconductor region 301 is a semiconductor region of the first conductivity type (N-type in this embodiment) and is provided on the first surface of the semiconductor layer 300. As shown in Figure 14, the first semiconductor region 301 in this embodiment is formed in a circular shape in the center of the pixel (partition) in a plan view. The cathode contact plug 326 is connected to the center of the first semiconductor region 301.

[0092] The fifth semiconductor region 305 is a semiconductor region of the second conductivity type (P-type in this embodiment) and is located on the light incident side (closer to the second surface) than the first semiconductor region 301. The fifth semiconductor region 305 is formed in layers to a predetermined depth so as to divide the epitaxial layer of the first conductivity type in one pixel (partition) into upper and lower halves. The periphery of the fifth semiconductor region 305 is in contact with the separation portion 330 surrounding the pixel. The epitaxial layer of the first conductivity type located on the first surface side of the fifth semiconductor region 305 is the sixth semiconductor region 306, and the epitaxial layer of the first conductivity type located on the second surface side is the eighth semiconductor region 308.

[0093] The first semiconductor region 301 of the first conductivity type and the fifth semiconductor region 305 of the second conductivity type form an avalanche multiplication region AM by a PN junction. The signal charge generated in the eighth semiconductor region 308 by photoelectric conversion is collected in the avalanche multiplication region AM. To improve the sensitivity of the APD201, it is preferable to increase the size of the eighth semiconductor region 308, which corresponds to the sensitivity region.

[0094] The seventh semiconductor region 307 is a first-conductivity semiconductor region formed around the first semiconductor region 301. The seventh semiconductor region 307 is also formed in a circular shape when viewed from above. Here, the impurity concentrations of the first semiconductor region 301, the seventh semiconductor region 307, and the sixth semiconductor region 306 are set to satisfy the relationship first semiconductor region 301 > seventh semiconductor region 307 > sixth semiconductor region 306. That is, the impurity concentration of the first semiconductor region 301 is the highest, and the impurity concentration of the seventh semiconductor region 307 is set to be between that of the first semiconductor region 307 and the sixth semiconductor region 306. This ensures an electrical connection between the cathode and the first semiconductor region 301 (i.e., APD201). In addition, the seventh semiconductor region 307 acts as a guard ring for electric field relaxation.

[0095] The ninth semiconductor region 309 is a second-conductivity type embedded layer provided across the entire second surface of the semiconductor layer 300. The ninth semiconductor region 309 plays a role in suppressing noise from the second surface side. Furthermore, a voltage VL from the anode wiring can be supplied to the ninth semiconductor region 309 via the second semiconductor region 302. In this case, a potential gradient for collecting charge can be formed.

[0096] Figure 16 is a cross-sectional view showing an example configuration in which a scintillator section 500 is stacked on a stacked photoelectric conversion section 100.

[0097] The photoelectric conversion substrate 11 (sensor substrate) has a first semiconductor layer 300 and a first wiring structure 320. The first semiconductor layer 300 has the photoelectric conversion element 102 described above formed on it. Pads 361 are exposed on the signal processing substrate 21. These pads 361 are aluminum electrodes used for connection to external devices. For example, they are connected to an external control unit 960 or an image processing unit (not shown) by bonding wires or ACF (Anisotropic Conducting Film) and FPC (Flexible Printed Circuits) 962.

[0098] The signal processing board 21 (circuit board) has a second semiconductor layer 420 and a second wiring structure 410. A sub-signal processing unit 103 having multiple semiconductor elements is formed on the second semiconductor layer 420. Wiring 401 related to the sub-signal processing unit 103 is formed on the second wiring structure 410.

[0099] The photoelectric conversion unit 100 is fabricated by stacking the photoelectric conversion substrate 11 and the signal processing substrate 21 so that their respective wiring structures 320 and 410 face each other. The electrical connection between the photoelectric conversion substrate 11 and the signal processing substrate 21 is made via the joint 328.

[0100] The scintillator section 500 is a pixel scintillator (or partition phosphor) separated to match the pixels 901 of the photoelectric conversion section 100. In other words, the scintillator section 500 is separated for each pixel. By using a pixel scintillator, the incidence of visible light photons 700 to adjacent pixels is reduced, making it possible to count the number of visible light photons 700 produced by one radiation photon in a single pixel.

[0101] The following materials can be used for the scintillator section 500. Materials that provide good radiation stopping and respond within 1us or less include CsI:Tl, CsI, Lu3Al5O12:Ce, PbWO4, Gd3Al2Ga3O12:Ce, (Lu,Y)2SiO5:Ce, and Gd2O2S:Tb(Pr).

[0102] A pixel scintillator is constructed by forming a partition substrate 954 through a Si wafer using a TSV (through-silicon via) process, creating a metal reflective layer 955 as needed, and then filling it with scintillator material. Besides using a Si wafer, the partition substrate can also be formed by depositing polyimide resin (PI). There are also methods for filling the scintillator material, such as heating and melting the scintillator material before filling, or using powdered scintillator material mixed with a binder resin before filling. When using a hygroscopic material like CsI as the scintillator material, it is advisable to use ALPET, a composite material made by laminating aluminum foil and polyester film, as the moisture-proof layer 952. Furthermore, when laminating the moisture-proof layer 952 to the partition substrate 954, bonding it with a reflective layer 953 made of a hot-melt sheet containing TiO2 allows for both moisture resistance and reflective performance to be achieved.

[0103] (Example 1) The configuration diagrams of the radiation detection panel shown in Figures 17 and 18 will be used to describe Example 1 of the fourth embodiment.

[0104] When radiation photon A in Figure 17 is incident on scintillator 956, it is multiplied by scintillator 956. Normally, a scintillator multiplies radiation photons into visible light photons by approximately 1000 times, but here we show a simplified case where it is multiplied by 2.

[0105] The amplified visible light photons C and B are incident on subpixels 3 and 5, respectively, and can be counted. On the other hand, radiation photons D incident on the edge of scintillator 956 are amplified into visible light photons E and F. Visible light photons E are incident on subpixel 1, and visible light photons F are reflected by the metal reflective layer 955 and incident on subpixel 1 in the same way as visible light photons E. Since two visible light photons, E and F, are incident on subpixel 1 simultaneously, a pile-up occurs, and even though two visible light photons are incident, they are counted as one. When scintillator 956 is separated by a partition substrate 954, the reflectivity of the metal reflective layer 955 changes the count of visible light photons emitted at the edge and the center of scintillator 956. Specifically, the edges cannot be counted correctly. Therefore, when estimating the energy of radiation photons from the count of visible light photons, the energy of radiation photons cannot be measured accurately.

[0106] Figure 18 is a diagram showing the configuration of the radiation detection panel in Example 1.

[0107] In the radiation detection panel of Example 1, the size of the photoelectric conversion elements 102 located at the ends of subpixels 1 and 9 of the scintillator 956 is halved. In other words, within the pixel 901, the size of the end subpixels 101 is halved. As a result, the light-receiving area of ​​the photoelectric conversion elements 102 in the end subpixels of the pixel is also halved. Therefore, of the visible light photons E and F that are multiplied from the radiation photons D incident on the end of the scintillator 956, only the visible light photons E are incident on subpixel 1. Since the size of the photoelectric conversion elements 102 in subpixel 1 is halved, the count is doubled in the subsequent sub-signal processing unit 103. By performing such processing, the visible light photons multiplied from the radiation photons D incident on the end of the scintillator 956 can also be accurately estimated. In Example 1, the size of the photoelectric conversion elements 102 is changed, but the density of subpixels 1 may also be changed. The density of subpixel 1 can be reduced only at the edges of scintillator 956, and then corrected by multiplying it by the reciprocal of the density in the subsequent sub-signal processing unit 103.

[0108] In this way, by changing the visible light detection sensitivity of subpixels per unit area within the phosphor-forming region of a single pixel, it becomes possible to accurately measure visible light photons. Specifically, in Example 1, by lowering the visible light detection sensitivity of subpixels per unit area at the edges of the scintillator 956 compared to the central part of the scintillator 956, it becomes possible to accurately measure visible light photons. In this example, the size of subpixels 101 at the edges of a single pixel 901 was reduced, but this is not limited to this; the size may be gradually reduced from the center to the edges. An example of this case is shown in Figure 23. Figure 23 shows the top surface of a single pixel (viewed from the Z-point in Figure 7).

[0109] (Example 2 of the fourth embodiment) Example 2 will be described using the configuration diagram of the radiation detection panel shown in Figure 19.

[0110] In Example 1, the visible light detection sensitivity of subpixels per unit area at the ends of the scintillator 956 is reduced by decreasing the size of the photoelectric conversion element 102. In Example 2, however, a light-shielding layer 970, which is a shielding member, is placed on top of the photoelectric conversion element 102. By placing the light-shielding layer 970 only at the ends of the scintillator, the visible light detection sensitivity of subpixels per unit area for subpixels 1 and 9 is reduced. By including the light-shielding layer 970, the same effect as in Example 1 is obtained without changing the photoelectric conversion element 102 of the subpixels. The light-shielding layer 970 can be made by reducing the aperture ratio of the photoelectric conversion element 102 using metal wiring, or by placing organic or inorganic materials that absorb visible light between the scintillator 956 and the photoelectric conversion element 102. In this example as well, the aperture area of ​​the light-shielding layer may be reduced from the center to the edge within a single pixel 901 (see Figure 24). Furthermore, the opening 971 is an opening provided in the light-shielding layer 970, and the size of the opening 971 indicates the size of the opening area.

[0111] (Example 3 of the fourth embodiment) Example 3 will be described using the configuration diagram of the radiation detection panel shown in Figure 20.

[0112] In Examples 1 and 2, the size and light-shielding area of ​​the photoelectric conversion element 102 at the end of the scintillator 956 are changed, but in Example 3, the photoelectric conversion element 102 at the end of the scintillator 956 is divided. In other words, the photoelectric conversion element 102 is divided so that the density of subpixels at the end of the pixel is higher. By dividing it, visible light photons emitted in the vicinity can be accurately measured, and pile-up is less likely to occur.

[0113] Dividing all subpixels within a pixel into two increases power consumption, but by dividing only the edges of the scintillator 956, it is possible to prevent pile-up while keeping the increase in power consumption to a minimum.

[0114] (Example 4 of the fourth embodiment) Example 4 will be described using the configuration diagram of the radiation detection panel shown in Figure 21.

[0115] In Example 4, the driving method of the sub-signal processing unit 103 is varied between the ends and the center of the scintillator 956. Visible light photons E and F may emit light simultaneously, or their emission timing may differ depending on the time response. Therefore, by speeding up the reset timing of the active quench element of the sub-signal processing unit 103, visible light photons E and F can be counted separately. For example, clock signals pSetA and pSetI for reset are reset at 20MHz, while clock signals pSetB to pSetH are operated at 10MHz. In other words, the sampling rate of the sub-signal processing unit is made different for subpixels at the ends of the pixel and subpixels in the center. By varying the processing capability of the sub-signal processing unit in this way, pile-up can be suppressed, and power consumption can be reduced. Speeding up the clock signal increases power consumption, but because the clock signal is only speeded up partially, the increase in power consumption is kept to a minimum. By changing the driving method at the edges and center of the scintillator 956 in this way, it becomes possible to accurately count visible light photons while reducing power consumption. This type of driving effectively means increasing the visible light detection sensitivity of subpixels per unit area.

[0116] Furthermore, by continuously applying one of the clock signals pSetA to pSetI (keeping the photoelectric conversion element 102 in a reset state), the operation of a specific photoelectric conversion element 102 can be stopped. In Examples 1 to 3, the size of the photoelectric conversion element 102 was physically changed or a light-shielding layer was provided, but by stopping the operation of a specific photoelectric conversion element 102, the visible light detection sensitivity of subpixels per unit area can also be reduced.

[0117] Furthermore, the visible light detection sensitivity of subpixels per unit area can be changed by halving the size of the photoelectric conversion element 102 or by stopping the operation of the photoelectric conversion element 102. In this case, the visible light detection sensitivity of subpixels per unit area can also be adjusted by arranging the subpixels in a staggered (alternating) pattern, rather than arranging them at all ends of the scintillator 956.

[0118] Furthermore, the following configuration is also possible in Embodiment 4.

[0119] If a visible light-absorbing material such as a Si wafer is used for the partition substrate 954, the visible light emitted by the scintillator 956 will be absorbed by the partition substrate 954. As a result, the end of the scintillator 956, which is closer to the partition substrate 954, may have fewer visible light photons than the center of the scintillator 956. When visible light is absorbed by the partition substrate 954 in this way, the size of the photoelectric conversion elements 102 should be made smaller in the center of the scintillator 956 than at the ends of the scintillator 956. Alternatively, the density of photoelectric conversion elements 102 may be higher in the center of the scintillator 956 than at the ends of the scintillator 956. The size and density of the photoelectric conversion elements 102 can be changed between the center and ends of the scintillator 956, and the subsequent sub-signal processing unit 103 can correct this by multiplying by the reciprocal of the size and density of the photoelectric conversion elements 102.

[0120] Furthermore, if visible light is absorbed by the partition substrate 954, a light-shielding layer 970 is placed on the photoelectric conversion element 102 to shield visible light, making the shielding area at the edges of the scintillator 956 smaller than that at the center of the scintillator 956. Even if the partition substrate 954 is a material that absorbs visible light, visible light can be detected uniformly at the center and edges of the scintillator 956, thereby suppressing pile-up.

[0121] Furthermore, if visible light is absorbed by the partition substrate 954, the timing for resetting the active quench element of the sub-signal processing unit 103 may be set to be earlier in the central part of the scintillator 956 than at the edges of the scintillator 956.

[0122] For example, the reset clock signals pSetA and pSetI are set to 10MHz. Clock signals pSetB to pSetH are set to 20MHz to suppress pile-up and also reduce power consumption. The partition substrate 954 is made of a material that reflects visible light and a material that absorbs visible light, and by using opposite methods, pile-up can be suppressed.

[0123] [Application Forms] Figure 25 is a conceptual diagram of an X-ray diagnostic system (radiation imaging system) using a radiation imaging device according to the present disclosure. X-rays 711, as radiation generated in the X-ray tube 710 (radiation source), pass through the chest 721 of the patient or subject 720 and enter the radiation imaging device 100 of the present disclosure, which includes a scintillator unit 200. These incident X-rays contain information about the inside of the patient's body. The scintillator unit 200 emits light in response to the incident X-rays, and this is photoelectrically converted to obtain electrical information. This information is converted into a digital signal and processed as an image by an image processor 730, which is a signal processing means, and can be observed on a display 740, which is a display means in the control room (X-ray room). The radiation imaging system comprises at least a radiation imaging device 100 and an image processor 730 that processes signals from the radiation imaging device 100.

[0124] Furthermore, images processed by the image processor 730 can be transmitted to a remote location (for example, a doctor's room) via a transmission means such as a telephone line 750. The transmitted images can be displayed on a display 741, which is a display means in the doctor's room, or saved on a recording means such as an optical disc, so that a doctor in a remote location can make a diagnosis using the transmitted images. In addition, the transmitted images can also be recorded on a recording medium, film 761, by a recording means, film processor 760.

[0125] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. For example, although the embodiments described above were described using a radiation imaging device as an example, it can also be applied to imaging devices equipped with subpixels using photoelectric conversion elements that convert visible light into electric charge. Accordingly, claims are attached to disclose the scope of the invention.

[0126] Furthermore, the disclosures herein include the following imaging devices, radiation imaging devices, and radiation imaging systems.

[0127] (Item 1) A radiation imaging apparatus having a scintillator unit that converts incident radiation into visible light, and a photoelectric conversion unit that converts the visible light into an electrical signal, The radiation imaging apparatus is characterized in that the scintillator section comprises a first visible light absorbing member that separates a plurality of scintillators included in the scintillator section in a direction perpendicular to the incident direction of the radiation, and a second visible light absorbing member provided on the incident surface of the radiation.

[0128] (Item 2) The first visible light absorbing member is either glass or silicon. The radiation imaging apparatus according to item 1, characterized in that the second visible light absorbing member is one of glass, amorphous carbon, CFRP, resin film, aluminum, or titanium.

[0129] (Item 3) The radiation imaging apparatus according to item 1, characterized in that a third visible light absorbing member is arranged between the scintillator section and the photoelectric conversion section.

[0130] (Item 4) The radiation imaging apparatus according to item 3, characterized in that the third visible light absorbing member is an FOP.

[0131] (Item 5) The radiation imaging apparatus according to item 1, characterized in that the photoelectric conversion unit has a fourth visible light absorbing member provided on the side into which the visible light is incident on the photoelectric conversion unit.

[0132] (Item 6) The photoelectric conversion unit has a photoelectric conversion element that converts the visible light into an electrical signal. The radiation imaging apparatus according to item 5, characterized in that the fourth visible light absorbing member is a metal film or an organic film formed at a position that reduces the visible light incident on the photoelectric conversion element.

[0133] (Item 7) The radiation imaging apparatus according to item 1, characterized in that the first visible light absorbing member and the second visible light absorbing member are integrally formed, and the first visible light absorbing member and the second visible light absorbing member are made of silicon.

[0134] (Item 8) A radiation source that emits radiation, A radiation imaging system characterized by comprising a radiation imaging device according to any one of items 1 to 7, which detects radiation generated by the aforementioned radiation source.

[0135] (Item 9) A scintillator panel that converts incident radiation into visible light, A scintillator panel characterized by having a first visible light absorbing member that separates a plurality of scintillators included in the scintillator panel in a direction perpendicular to the incident direction of the radiation, and a second visible light absorbing member provided on the incident surface of the radiation.

[0136] (Item 10) A scintillator that generates visible light when irradiated with radiation, A plurality of subpixels each having a photoelectric conversion element that generates an electric charge upon receiving visible light generated by the scintillator and a sub-signal processing unit that generates an electrical signal upon receiving the electric charge generated by the photoelectric conversion element, and a plurality of pixel pixels each having a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, A radiation imaging device equipped with, An imaging device characterized in that the visible light receiving area of ​​the photoelectric conversion element differs among the plurality of subpixels.

[0137] (Item 11) The radiation imaging apparatus according to item 10, characterized in that the scintillator is separated for each pixel.

[0138] (Item 12) The radiation imaging apparatus according to item 10 or 11, characterized in that, among the multiple subpixels provided by the pixel, the light-receiving area of ​​the subpixel located at the edge of the pixel and the light-receiving area of ​​the subpixel located in the center are different.

[0139] (Item 13) The radiation imaging apparatus according to any one of items 10 to 12, characterized in that a plurality of subpixels provided by the aforementioned pixel are arranged within the pixel so as to have different densities.

[0140] (Item 14) A radiation imaging apparatus according to any one of items 10 to 13, characterized in that a visible light shielding member is provided between the photoelectric conversion elements of a plurality of subpixels provided in the pixel and the scintillator, and the aperture area of ​​the shielding member differs for each of the plurality of subpixels.

[0141] (Item 15) A scintillator that generates visible light when irradiated with radiation, A plurality of subpixels each having a photoelectric conversion element that generates an electric charge upon receiving visible light generated by the scintillator and a sub-signal processing unit that generates an electrical signal upon receiving the electric charge generated by the photoelectric conversion element, and a plurality of pixel pixels each having a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, A radiation imaging device equipped with, The imaging apparatus according to any one of items 10 to 14, characterized in that the processing capability of the sub-signal processing unit for processing the charge differs for each of the multiple subpixels.

[0142] (Item 16) The radiation imaging apparatus according to any one of items 10 to 15, characterized in that the sub-signal processing unit of a plurality of sub-pixels provided in the aforementioned pixel has a different driving method for the plurality of sub-pixels.

[0143] (Item 17) The radiation imaging apparatus according to any one of items 10 to 16, characterized in that the sub-signal processing units of the plurality of sub-pixels provided in the pixel have different sampling rates for receiving the charge generated by the photoelectric conversion element in the plurality of sub-pixels.

[0144] (Item 18) A scintillator that generates visible light when irradiated with radiation, A photoelectric conversion unit that receives visible light generated by the scintillator and generates an electrical signal, A radiation imaging apparatus comprising: a signal processing unit that classifies and outputs electrical signals generated by the photoelectric conversion unit; The photoelectric conversion unit comprises a plurality of subpixels, each having a photoelectric conversion element that generates an electric charge upon receiving visible light, and a sub-signal processing unit that generates an electric signal upon receiving the electric charge generated by the photoelectric conversion element. The radiation imaging apparatus is characterized in that the plurality of subpixels are arranged such that their visible light detection sensitivities per unit area of ​​the photoelectric conversion unit are different from each other.

[0145] (Item 19) A radiation imaging apparatus comprising a plurality of pixel pixels, each having a photoelectric conversion element that generates an electric charge upon receiving visible light and a sub-signal processing unit that generates an electrical signal upon receiving the charge generated by the photoelectric conversion element, and a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, An imaging device characterized in that the visible light receiving area of ​​the photoelectric conversion element differs among the plurality of subpixels.

[0146] (Item 20) A radiation imaging apparatus comprising a plurality of pixel pixels, each having a photoelectric conversion element that generates an electric charge upon receiving visible light and a sub-signal processing unit that generates an electrical signal upon receiving the charge generated by the photoelectric conversion element, and a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, An imaging apparatus characterized in that the processing capability of the sub-signal processing unit for processing the charge differs for each of the multiple subpixels.

[0147] (Item 21) A radiation imaging system comprising a radiation imaging device described in any one of items 10 to 18, and a control device that acquires image data from the radiation imaging device and processes the image data.

[0148] (Item 22) An imaging system comprising an imaging device described in item 19 or 20, and a control device that acquires image data from the imaging device and processes the image data. [Explanation of symbols]

[0149] 980 Radiation Imaging System 990 Radiation imaging device 984 Radiation Generator 985 Radiation 500 Scintillator section 11 Photoelectric conversion substrate 21 Signal Processing Board 102 Photoelectric conversion element 956 Scintillator

Claims

1. A radiation imaging apparatus having a scintillator unit that converts incident radiation into visible light, and a photoelectric conversion unit that converts the visible light into an electrical signal, The radiation imaging apparatus is characterized in that the scintillator section comprises a first visible light absorbing member that separates a plurality of scintillators included in the scintillator section in a direction perpendicular to the incident direction of the radiation, and a second visible light absorbing member provided on the incident surface of the radiation.

2. The first visible light absorbing member is either glass or silicon. The radiation imaging apparatus according to claim 1, characterized in that the second visible light absorbing member is one of glass, amorphous carbon, CFRP, resin film, aluminum, or titanium.

3. The radiation imaging apparatus according to claim 1, characterized in that a third visible light absorbing member is arranged between the scintillator section and the photoelectric conversion section.

4. The radiation imaging apparatus according to claim 3, characterized in that the third visible light absorbing member is an FOP.

5. The radiation imaging apparatus according to claim 1, characterized in that the photoelectric conversion unit has a fourth visible light absorbing member provided on the side into which the visible light is incident on the photoelectric conversion unit.

6. The photoelectric conversion unit has a photoelectric conversion element that converts the visible light into an electrical signal. The radiation imaging apparatus according to claim 5, characterized in that the fourth visible light absorbing member is a metal film or an organic film formed at a position that reduces the visible light incident on the photoelectric conversion element.

7. The radiation imaging apparatus according to claim 1, characterized in that the first visible light absorbing member and the second visible light absorbing member are integrally formed, and the first visible light absorbing member and the second visible light absorbing member are made of silicon.

8. A radiation source that emits radiation, A radiation imaging system comprising a radiation imaging device according to any one of claims 1 to 7, which detects radiation generated by the radiation source.

9. A scintillator panel that converts incident radiation into visible light, A scintillator panel characterized by having a first visible light absorbing member that separates a plurality of scintillators included in the scintillator panel in a direction perpendicular to the incident direction of the radiation, and a second visible light absorbing member provided on the incident surface of the radiation.

10. A scintillator that generates visible light when irradiated with radiation, A plurality of subpixels each having a photoelectric conversion element that generates an electric charge upon receiving visible light generated by the scintillator and a sub-signal processing unit that generates an electrical signal upon receiving the electric charge generated by the photoelectric conversion element, and a plurality of pixel pixels each having a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, A radiation imaging device equipped with, A radiation imaging device characterized in that the visible light receiving area of ​​the photoelectric conversion element differs among the plurality of subpixels.

11. The radiation imaging apparatus according to claim 10, characterized in that the scintillator is separated for each pixel.

12. The radiation imaging apparatus according to claim 10, characterized in that, among the plurality of subpixels provided by the pixel, the light-receiving area of ​​the subpixel located at the edge of the pixel and the subpixel located in the center are different.

13. The radiation imaging apparatus according to claim 10, characterized in that a plurality of subpixels provided by the aforementioned pixel are arranged within the pixel so as to have different densities.

14. The radiation imaging apparatus according to claim 10, wherein a visible light shielding member is provided between the photoelectric conversion elements of a plurality of subpixels provided in the pixel and the scintillator, and the aperture area of ​​the shielding member differs for each of the plurality of subpixels.

15. A scintillator that generates visible light when irradiated with radiation, A plurality of subpixels each having a photoelectric conversion element that generates an electric charge upon receiving visible light generated by the scintillator and a sub-signal processing unit that generates an electrical signal upon receiving the electric charge generated by the photoelectric conversion element, and a plurality of pixel pixels each having a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, A radiation imaging device equipped with, A radiation imaging apparatus characterized in that the processing capability of the sub-signal processing unit for processing the charge differs for each of the multiple subpixels.

16. The radiation imaging apparatus according to claim 15, characterized in that the scintillator is separated for each pixel.

17. The radiation imaging apparatus according to claim 15, characterized in that the sub-signal processing units of the plurality of sub-pixels provided in the aforementioned pixel have different driving methods for the plurality of sub-pixels.

18. The radiation imaging apparatus according to claim 14, characterized in that the sub-signal processing units of the plurality of sub-pixels provided in the pixel have different sampling rates for receiving the charge generated by the photoelectric conversion element in the plurality of sub-pixels.

19. A scintillator that generates visible light when irradiated with radiation, A photoelectric conversion unit that receives visible light generated by the scintillator and generates an electrical signal, A radiation imaging apparatus comprising: a signal processing unit that classifies and outputs electrical signals generated by the photoelectric conversion unit; The photoelectric conversion unit comprises a plurality of subpixels, each having a photoelectric conversion element that generates an electric charge upon receiving visible light, and a sub-signal processing unit that generates an electric signal upon receiving the electric charge generated by the photoelectric conversion element. The radiation imaging apparatus is characterized in that the plurality of subpixels are arranged such that their visible light detection sensitivities per unit area of ​​the photoelectric conversion unit are different from each other.

20. A radiation imaging apparatus comprising a plurality of pixel pixels, each having a photoelectric conversion element that generates an electric charge upon receiving visible light and a sub-signal processing unit that generates an electrical signal upon receiving the charge generated by the photoelectric conversion element, and a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, An imaging device characterized in that the visible light receiving area of ​​the photoelectric conversion element differs among the plurality of subpixels.

21. A radiation imaging apparatus comprising a plurality of pixel pixels, each having a photoelectric conversion element that generates an electric charge upon receiving visible light and a sub-signal processing unit that generates an electrical signal upon receiving the charge generated by the photoelectric conversion element, and a signal processing unit that processes the electrical signals generated by the sub-signal processing units of the plurality of subpixels to generate a pixel signal, An imaging apparatus characterized in that the processing capability of the sub-signal processing unit for processing the charge differs for each of the multiple subpixels.

22. A radiation imaging system comprising a radiation imaging device according to claim 10, and a control device that acquires image data from the radiation imaging device and processes the image data.

Images