JP2013172101A - Radiation detector, radiographic imaging device, and radiographic imaging system - Google Patents

Abstract

Redundancy with respect to disconnection of a bias wiring is ensured and pixel unevenness is suppressed.
A sub-bias wiring is provided for each row of pixels, and bias wirings for applying a bias voltage to pixels in the same row of adjacent columns are connected by the sub-bias wiring. Yes. When a disconnection occurs in the bias wiring 25, the bias voltage is applied from another bias wiring 25 through the sub-bias wiring 40 to the pixel 20 to which no bias voltage is applied from the bias wiring 25. When the radiation detector 10 is irradiated with intense light locally and a charge is generated in the pixel 20, the pixel 20 connected to the pixel 20 connected to the same bias wiring 25 and the sub-bias wiring 40 through the sub-bias wiring 40. Since current flows between the pixels 20 adjacent to each other in the row direction, the voltage drop ΔV per pixel 20 can be suppressed, and the unevenness can be formed into an area, so that it is difficult to visually recognize the unevenness. Can do.
[Selection] Figure 3

Description

  The present invention relates to a radiation detector, a radiation image capturing apparatus, and a radiation image capturing system, and more particularly to a radiation detector, a radiation image capturing apparatus, and a radiation image capturing system for capturing a medical radiation image.

  2. Description of the Related Art Conventionally, a radiographic image capturing apparatus that captures a radiographic image for medical diagnosis or the like is known. The radiation image capturing apparatus captures a radiation image by detecting radiation that has been irradiated from the radiation irradiating apparatus and transmitted through the subject with a radiation detector. The radiographic image capturing apparatus captures a radiographic image by collecting and reading out charges generated according to the irradiated radiation.

  Such a radiographic imaging apparatus includes a radiation detector that detects radiation. As the radiation detector, a sensor unit including a photoelectric conversion element that generates charges when irradiated with radiation or light converted from radiation, and an electric signal corresponding to the charges by reading out the charges generated in the sensor unit There is a radiation detector provided with a switching element that outputs to the signal wiring. In the radiation detector, a radiation image is generated (captured) based on the electrical signal (charge) output to the signal wiring.

  FIG. 11 shows a schematic configuration diagram of a specific example of such a conventional radiation detector. Note that FIG. 11 shows only 3 pixels × 3 pixels (for 9 pixels). In general, the signal wiring 3 is provided for each column or row of the pixels 20. In FIG. 11, the signal wiring 3 is provided for each column. Further, in such a conventional radiation detector 1000, a bias wiring 25 for applying a bias voltage to each pixel 20 is provided. In general, the bias wiring 25 is provided in parallel with the signal wiring 3 so as not to cross at least in order to suppress noise due to parasitic capacitance with the signal wiring. Therefore, in the radiation detector 1000 illustrated in FIG. 11, the bias wiring 25 is provided for each column of the pixels 20.

  In such a conventional radiation detector 1000, when the bias wiring 25 is disconnected in the middle, a bias voltage is applied to the pixel 20 provided ahead of the disconnection location (a position ahead when viewed from the bias power supply 110). There is a case where these pixels 20 become defective pixels and cannot be applied, resulting in a line defect.

  For this reason, a technique for ensuring redundancy when the bias wiring is disconnected is known. For example, in Patent Document 1, a bias line is provided for each pixel column in parallel with a signal transfer line, and an end of the bias line opposite to the side connected to the common electrode driver for bias application is provided. A semiconductor device is described in which the ends of other bias lines are electrically connected to each other by redundant wiring. Further, in Patent Document 2, if the reading device is only on one side, or if the bias wiring is disconnected, the previous signal does not come out from the disconnected portion, so the bias wiring is connected to the two reading devices. A technique for preventing this by connecting is described.

JP 2000-148037 A JP 2004-179645 A

  However, in the techniques described in Patent Document 1 and Patent Document 2, there is a concern that appropriate redundancy is not ensured in a case where a plurality of disconnections occur in one bias wiring.

  In addition, when intense radiation (light) is locally applied to the radiation detector, a large charge is generated in the photoelectric conversion element, and a current flows through the bias wiring. Therefore, the same bias wiring as that of the irradiated pixel is used. A voltage drop may occur in adjacent pixels connected to, and as a result, unevenness may occur along the bias wiring. In the conventional radiation detector 1000 shown in FIG. 11 described above, there is a problem that unevenness occurs in the column direction.

  The present invention has been made in order to solve the above-described problems, and can provide a radiation detector, a radiation imaging apparatus, and radiation that can ensure redundancy with respect to disconnection of the bias wiring and suppress pixel unevenness. An object is to provide an image photographing system.

  In order to achieve the above object, a radiation detector according to the present invention includes a sensor unit that generates a charge corresponding to the dose of irradiated radiation, and an electrical signal corresponding to the charge by reading the charge from the sensor unit. A plurality of pixels arranged in a matrix each having a switching element to output, a plurality of signal wirings provided for each column or row of the plurality of pixels, and for outputting the electrical signal; and the signal wirings; Provided for each of the plurality of pixels that output the electrical signal to the same signal wiring so as not to cross each other, and a bias voltage applied from a bias power supply is applied to each of the plurality of pixels for each column or row. A plurality of first bias wirings to be supplied to the sensor section of the pixel and a second via connecting a plurality of first bias wirings provided in a pixel region including the plurality of pixels and arranged adjacent to each other. It includes scan lines and the, the.

  The radiation detector according to the present invention is a matrix provided with a sensor unit that generates a charge according to the dose of irradiated radiation, and a switching element that reads the charge from the sensor unit and outputs an electrical signal according to the charge. A plurality of signal wirings are provided for each of a plurality of pixels arranged in a row and a plurality of pixel columns, and output electric signals. A plurality of first bias lines and a plurality of second bias lines are provided. The first bias wiring is provided for each column of the plurality of pixels so as not to cross the signal wiring, and the bias voltage applied from the bias power source is supplied to the sensor unit of the plurality of pixels for each column of the plurality of pixels. . A plurality of second bias wirings are provided in a pixel region including a plurality of pixels, and a first bias wiring that supplies a bias voltage to the pixels and a first bias voltage that supplies a bias voltage to pixels in a column adjacent to the pixel. Connect to the bias wiring.

  As described above, in the present invention, the first bias wiring that supplies the bias voltage to the pixel and the first bias wiring that supplies the bias voltage to the pixel in the column adjacent to the pixel are connected by the second bias wiring. Thus, the bias voltage is applied to the pixel from the first bias wiring that supplies the bias voltage to the pixels in the column adjacent to the pixel via the second bias wiring. In addition, the current locally generated in the pixels 20 due to local light irradiation that causes image quality unevenness is connected to the pixels in the adjacent row via the first bias wiring and via the second bias wiring. Since it flows between pixels in adjacent columns, unevenness can be suppressed. Thereby, it is possible to ensure redundancy with respect to the disconnection of the bias wiring and to suppress pixel unevenness.

  In the present invention, it is preferable that the second bias wiring is thinner than the first bias wiring.

  In the present invention, it is preferable that the second bias wiring is made of a transparent conductor.

  In the present invention, it is preferable that the first bias wiring is made of a transparent conductor.

  In the present invention, the pixel, the signal wiring, the first bias wiring, and the second bias wiring are formed by a stacked structure in which a layer including a metal layer or a conductive layer is stacked on a substrate, The second bias wiring is preferably formed of a conductive layer stacked at a position away from the substrate from the layer including the metal layer.

  Further, in the present invention, each of the pixels includes the switching element stacked on a substrate, and the sensor unit stacked on a first planarization layer that planarizes a step formed by the switching element, Between the signal wiring layer and the second bias wiring layer, at least the first flattening layer and a second flattening layer for flattening a step formed by the sensor unit are provided. Preferably it is.

  Further, in the present invention, the pixel, the signal wiring, the first bias wiring, and the second bias wiring are formed by a stacked structure in which each layer is stacked on a substrate, and the signal wiring layer, The second bias wiring layer is preferably provided at a distance of 2 μm or more in the stacking direction.

  In the present invention, it is preferable that the second bias wiring is provided in a region other than the region where the switching element is provided.

  In the present invention, it is preferable that the second bias wiring is provided with a constant period for the plurality of pixels.

  Moreover, the radiographic imaging device of the present invention outputs a radiographic image by outputting an electrical signal to a signal wiring from the radiation detector of the present invention and a pixel of the radiation detector, and generating a radiographic image corresponding to the electrical signal. Photographing means for photographing.

  Moreover, the radiographic imaging system of this invention is equipped with a radiation irradiation apparatus and the radiographic imaging apparatus of this invention which image | photographs a radiographic image with the radiation irradiated from the said radiation irradiation apparatus.

  According to the present invention, it is possible to obtain an effect of ensuring redundancy with respect to the disconnection of the bias wiring and suppressing pixel unevenness.

It is a schematic block diagram which shows schematic structure of an example of the radiographic imaging system which concerns on this Embodiment. It is a block diagram which shows an example of the whole structure of the radiographic imaging apparatus which concerns on this Embodiment. It is a top view which shows an example of a structure of the radiation detector concerning this Embodiment. FIG. 4 is a cross-sectional view taken along line AA of an example of the radiation detector according to the present exemplary embodiment illustrated in FIG. 3. FIG. 4 is a cross-sectional view taken along line B-B of an example of the radiation detector according to the present exemplary embodiment illustrated in FIG. 3. It is CC sectional view taken on the line of an example of the radiation detector which concerns on this Embodiment shown in FIG. It is explanatory drawing for demonstrating the case where a disconnection generate | occur | produces in the bias wiring of the radiation detector which concerns on this Embodiment. It is explanatory drawing for demonstrating the case where intense light is irradiated locally on the radiation detector which concerns on this Embodiment. It is a top view which shows another example of the other structure of the radiation detector which concerns on this Embodiment. It is the DD sectional view taken on the line of an example of the radiation detector which concerns on this Embodiment shown in FIG. It is a top view which shows another example of the other structure of the conventional radiation detector. It is explanatory drawing for demonstrating the case where the intense light is locally irradiated to the conventional radiation detector.

  Hereinafter, an example of the present embodiment will be described with reference to the drawings.

  First, a schematic configuration of a radiographic image capturing system using a radiographic image capturing apparatus including the radiation detector according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of an example of a radiographic image capturing system according to the present embodiment.

  The radiographic imaging system 200 irradiates a subject 206 with radiation (for example, X-ray (X-ray) or the like), and radiation detection that detects radiation irradiated from the radiation irradiation device 204 and transmitted through the subject 206. The radiographic image capturing apparatus 100 including the device 10 and a control device 202 that instructs the radiographic image capturing apparatus 100 to acquire radiographic images while instructing radiographic image capturing. At a timing based on the control of the control device 202, the radiation image capturing device 100 is irradiated with the radiation carrying the image information by passing through the subject 206 irradiated from the radiation irradiation device 204 and positioned at the imaging position.

  Next, a schematic configuration of the radiation image capturing apparatus 100 of the present embodiment will be described. In the present embodiment, a case will be described in which the present invention is applied to an indirect conversion radiation detector 10 that once converts radiation such as X-rays into light and converts the converted light into electric charges. In the present embodiment, the radiographic image capturing apparatus 100 includes an indirect conversion type radiation detector 10. In FIG. 2, a scintillator that converts radiation into light is omitted.

  The radiation detector 10 includes a sensor unit 103 that receives light to generate electric charge, accumulates the generated electric charge, and a TFT switch 4 that is a switching element for reading out the electric charge accumulated in the sensor unit 103. A plurality of pixels 20 are arranged in a matrix. In this embodiment mode, charges are generated in the sensor unit 103 by irradiation with light converted by the scintillator.

  A plurality of pixels 20 are arranged in a matrix in one direction (scanning wiring direction in FIG. 2, hereinafter also referred to as “row direction”) and a direction intersecting the row direction (signal wiring direction in FIG. 2, hereinafter also referred to as “column direction”). Has been placed. In FIG. 2, the arrangement of the pixels 20 is shown in a simplified manner. For example, 1024 × 1024 pixels 20 are arranged in the row direction and the column direction.

  Further, the radiation detector 10 receives, on the substrate 1 (see FIG. 3), the scanning wiring 101 which is a plurality of control wirings for turning on / off the TFT switch 4 and the charges accumulated in the sensor unit 103. A plurality of signal wirings 3 for reading are provided so as to cross each other. In the present embodiment, one signal wiring 3 is provided for each pixel column in one direction, and one scanning wiring 101 is provided for each pixel column in the intersecting direction. When 1024 × 1024 are arranged in the column direction, 1024 signal wirings 3 and scanning wirings 101 are provided.

  Further, the radiation detector 10 is provided with a bias wiring 25 in parallel with each signal wiring 3. One end and the other end of the bias wiring 25 are connected in parallel, and one end is connected to a bias power supply 110 that supplies a predetermined bias voltage. The sensor unit 103 is connected to the bias wiring 25, and a bias voltage is applied via the bias wiring 25. The bias wiring 25 may be provided so as not to cross at least the signal wirings 3 and may not be in parallel.

  A scanning signal for switching each TFT switch 4 flows through the scanning wiring 101. In this way, each TFT switch 4 is switched (on / off) by the scan signal flowing through each scan line 101.

  When the TFT switch 4 of each pixel 20 is in the ON state, an electric signal corresponding to the electric charge accumulated in each pixel 20 flows through the signal wiring 3. More specifically, an electrical signal corresponding to the amount of charge accumulated by turning on any TFT switch 4 of the pixel 20 connected to the signal wiring 3 flows to each signal wiring 3.

  Each signal wiring 3 is connected to a signal detection circuit 105 that detects an electrical signal flowing out to each signal wiring 3. Each scan line 101 is connected to a scan signal control circuit 104 that outputs a scan signal for turning on / off the TFT switch 4 to each scan line 101. In FIG. 2, the signal detection circuit 105 and the scan signal control circuit 104 are shown in a simplified form. However, for example, a plurality of signal detection circuits 105 and a plurality of scan signal control circuits 104 are provided (for example, 256). The signal wiring 3 or the scanning wiring 101 is connected every time. For example, when 1024 signal wires 3 and 1024 scan wires 101 are provided, four scan signal control circuits 104 are provided, 256 scan wires 101 are connected, and four signal detection circuits 105 are provided 256. The signal wiring 3 is connected one by one.

  The signal detection circuit 105 incorporates an amplification circuit (not shown) for amplifying an input electric signal for each signal wiring 3. In the signal detection circuit 105, an electric signal input from each signal wiring 3 is amplified by an amplifier circuit and converted into a digital signal by an ADC (analog / digital converter).

  The signal detection circuit 105 and the scan signal control circuit 104 are subjected to predetermined processing such as noise removal on the digital signal converted by the signal detection circuit 105, and the signal detection circuit 105 is provided with a signal detection timing. A control unit 106 that outputs a control signal indicating the timing of outputting the scan signal is connected to the scan signal control circuit 104.

  The control unit 106 according to the present embodiment is configured by a microcomputer, and includes a nonvolatile storage unit including a CPU (Central Processing Unit), a ROM and a RAM, a flash memory, and the like. The control unit 106 generates and outputs a radiation image indicated by the irradiated radiation based on the electrical signal indicating the charge information input from the signal detection circuit 105.

  3 is a plan view showing a structure of 3 pixels × 3 pixels of the radiation detector 10 of the indirect conversion type according to the present embodiment, and FIG. 4 shows an A− of the pixel 20 in FIG. A cross-sectional view along line A is shown. 5 is a cross-sectional view taken along line BB of the pixel 20 in FIG. 3, and FIG. 6 is a cross-sectional view taken along line CC of the pixel 20 in FIG.

  As shown in FIG. 4, the pixel 20 includes a scanning wiring 101 (see FIG. 3) and a gate electrode 2 formed on an insulating substrate 1 made of alkali-free glass or the like. Are connected (see FIG. 3). The wiring layer in which the scanning wiring 101 and the gate electrode 2 are formed (hereinafter, this wiring layer is also referred to as “first signal wiring layer”) uses Al or Cu, or a laminated film mainly composed of Al or Cu. Although formed, it is not limited to these.

An insulating film 15 is formed on one surface of the first signal wiring layer, and a portion located on the gate electrode 2 functions as a gate insulating film in the TFT switch 4. The insulating film 15 is made of, for example, SiN _X or the like, and is formed by, for example, CVD (Chemical Vapor Deposition) film formation.

  On the gate electrode 2 on the insulating film 15, the semiconductor active layer 8 is formed in an island shape. The semiconductor active layer 8 is a channel portion of the TFT switch 4 and is made of, for example, an amorphous silicon film.

  A source electrode 9 and a drain electrode 13 are formed on these upper layers. In the wiring layer in which the source electrode 9 and the drain electrode 13 are formed, the signal wiring 3 is formed together with the source electrode 9 and the drain electrode 13. The source electrode 9 is connected to the signal wiring 3 (see FIG. 3). The wiring layer in which the source electrode 9, the drain electrode 13, and the signal wiring 3 are formed (hereinafter, this wiring layer is also referred to as “second signal wiring layer”) is a laminate mainly composed of Al or Cu, or Al or Cu. The film is formed using, but is not limited to these. Between the source electrode 9 and the drain electrode 13 and the semiconductor active layer 8, an impurity-added semiconductor layer (not shown) made of impurity-added amorphous silicon or the like is formed. These constitute the TFT switch 4 for switching. In the TFT switch 4, the source electrode 9 and the drain electrode 13 are reversed depending on the polarity of charges collected and accumulated by the lower electrode 11 described later.

A TFT protective film layer 30 is provided to cover the second signal wiring layer and to protect the TFT switch 4 and the signal wiring 3 over almost the entire area (substantially the entire area) where the pixel 20 is provided on the substrate 1. Is formed. The TFT protective film layer 30 is made of, for example, SiN _X or the like, and is formed by, for example, CVD film formation.

  A coating type interlayer insulating film 12 is formed on the TFT protective film layer 30. The interlayer insulating film 12 is a photosensitive organic material having a low dielectric constant (relative dielectric constant εr = 2 to 4) (for example, a positive photosensitive acrylic resin: a base made of a copolymer of methacrylic acid and glycidyl methacrylate). And a film obtained by mixing a naphthoquinonediazide-based positive photosensitive agent with a polymer). In the present embodiment, as a specific example, the thickness of the interlayer insulating film 12 is about 2 μm.

  In the radiation detector 10 according to the present exemplary embodiment, the interlayer insulating film 12 suppresses the capacitance between metals disposed in the upper and lower layers of the interlayer insulating film 12 to be low. In the present embodiment, the interlayer insulating film 12 functions as a flattening layer for flattening the step formed by the TFT switch 4. In the radiation detector 10 according to the present exemplary embodiment, a contact hole 17 is formed at a position facing the drain electrode 13 of the interlayer insulating film 12 and the TFT protective film layer 30.

  A lower electrode 11 of the sensor unit 103 is formed on the interlayer insulating film 12 so as to cover the pixel region while filling the contact hole 17, and the lower electrode 11 is connected to the drain electrode 13 of the TFT switch 4. ing. If the semiconductor layer 21 described later is as thick as about 1 μm, the lower electrode 11 has almost no material limitation as long as it has conductivity. For this reason, there is no problem if it is formed using a conductive metal such as an Al-based material or a conductive oxide such as ITO.

  On the other hand, when the semiconductor layer 21 is thin (around 0.2 to 0.5 μm), light is not sufficiently absorbed by the semiconductor layer 21, so that an increase in leakage current due to light irradiation to the TFT switch 4 is prevented. An alloy mainly composed of a light-shielding metal or a laminated film is preferable.

  A semiconductor layer 21 that functions as a photodiode is formed on the lower electrode 11. In the present embodiment, a PIN structure photodiode in which an n + layer, an i layer, and a p + layer (n + amorphous silicon, amorphous silicon, p + amorphous silicon) are stacked is employed as the semiconductor layer 21, and the n + layer 21A is formed from the lower layer. , I layer 21B and p + layer 21C are sequentially stacked. The i layer 21 </ b> B generates charges (a pair of free electrons and free holes) when irradiated with light. The n + layer 21A and the p + layer 21C function as contact layers, and electrically connect the lower electrode 11 and an upper electrode 22 (described later) and the i layer 21B.

  On each semiconductor layer 21, an upper electrode 22 is formed individually. For the upper electrode 22, for example, a material having high light transmittance such as ITO or IZO (zinc oxide indium) is used. In the radiation detector 10 according to the present exemplary embodiment, the sensor unit 103 includes the upper electrode 22, the semiconductor layer 21, and the lower electrode 11.

  On the interlayer insulating film 12, the semiconductor layer 21, and the upper electrode 22, a coating type interlayer insulating film 23 is formed so as to have a part of the opening 27 </ b> A corresponding to the upper electrode 22 and cover each semiconductor layer 21. Yes. In the present embodiment, the interlayer insulating film 23 functions as a planarization layer that planarizes the step formed by the sensor unit 103. The interlayer insulating film 23 has substantially the same configuration as the interlayer insulating film 12, and is formed with a thickness of 1 to 4 μm. In the present embodiment, as a specific example, the film thickness of the interlayer insulating film 23 is about 2 μm.

  A bias wiring 25 is formed on the interlayer insulating film 23. The bias wiring 25 is preferably a transparent conductor, Al or Cu, an alloy mainly composed of Al or Cu, or a laminated film, and particularly preferably a transparent conductor. As the transparent conductor, for example, a highly light-transmitting conductor such as ITO or IZO (zinc indium oxide) is preferable. The bias wiring 25 has a contact pad 27 formed in the vicinity of the opening 27 </ b> A and is electrically connected to the upper electrode 22 through the opening 27 </ b> A of the interlayer insulating film 23.

  In the present embodiment, the sub-bias wiring 40 is formed on the interlayer insulating film 23. As with the bias wiring 25, the sub-bias wiring 40 is preferably a transparent conductor, Al or Cu, an alloy mainly composed of Al or Cu, or a laminated film, and particularly preferably a transparent conductor. As the transparent conductor, for example, a highly light-transmitting conductor such as ITO or IZO (zinc indium oxide) is preferable.

  The sub-bias wiring 40 of the present embodiment is formed so as to connect the pixels 20 in the same row, which are adjacent columns, specifically, the bias wiring 25 that applies a bias voltage to the pixels 20. Therefore, in this embodiment, as shown in FIG. 3, the sub-bias wiring 40 is formed for each row. In order to connect the pixels 20 (bias wiring 25) of adjacent columns, the sub-bias wiring 40 is wired on the upper layer of the signal wiring 3 so as to straddle the signal wiring 3 as shown in FIG. The sub-bias wiring 40 is preferably thinner in order to suppress the formation of parasitic capacitance with the signal wiring 3, and in this embodiment, it is thinner than the bias wiring 25 (details will be described later).

  In the radiation detector 10 formed in this way, a protective film is formed of an insulating material having a lower light absorption as required, and an adhesive resin having a low light absorption is used on the surface thereof to form GOS or A scintillator made of CsI or the like is attached.

  Next, the action brought about by the sub-bias wiring 40 in the radiation detector 10 of the present embodiment will be described with a specific example.

  First, the action for the disconnection of the bias wiring 25 will be described. In the radiation detector 1000 that does not include the conventional sub-bias wiring 40 shown in FIG. 11, when the bias wiring 25 is disconnected, the bias power supply 110 is connected to the pixel 20 on the other side (the side viewed from the bias power supply 110 side). Thus, no bias voltage is applied, resulting in a defective pixel, resulting in a line defect. Even when the end of the bias wiring 25 provided for each row of the pixels 20 on the side opposite to the bias power supply 110 side is connected (see FIG. 3 in the present embodiment), the end on the opposite side is connected. A bias voltage is applied from the portion, but when a disconnection occurs in a plurality of locations of one bias wiring 25, the bias voltage is not applied to the pixels 20 between the disconnection locations.

  On the other hand, in the radiation detector 10 of the present embodiment shown in FIG. 3 and FIG. 7, the pixel 20 in the A row and the second column (hereinafter referred to as the pixel 20 (A 2)). 2) and in the pixel 20 (C2) (refer to FIG. 7, disconnection point X, disconnection point Y), when the bias wiring 25 is disconnected, the pixel 20 (B2) is isolated and the bias wiring No bias voltage is supplied from 25. However, in this embodiment, the sub-bias wiring 40 adjoins the first-line bias wiring 25 (pixel 20 (B1)) and the third-column bias wiring 25 (pixel 20 (B3)) to the pixel 20 (B2). The bias wiring 25 is connected. Therefore, a bias voltage is applied to the pixel 20 (B2) via the sub-bias wiring 40 by the bias wiring 25 (pixel 20 (B1)) in the first column and the bias wiring 25 (pixel 20 (B2)) in the third column. Is done.

  Therefore, in this embodiment, the pixel 20 (B2) and the pixel 20 (C2) do not become defective pixels, and no line defect occurs.

  In the radiation detector 10, when the end of the bias wiring 25 opposite to the bias power supply 110 side is not connected, the bias wiring 25 is disconnected within the pixel 20 (A 2) (FIG. 7, disconnection location X When the reference) occurs, the bias voltage is not supplied from the bias wiring 25 to the pixel 20 (B2) and the pixel 20 (C2) ahead of the disconnection portion.

  Even in such a case, the bias voltage is applied to the pixel 20 (B2) through the sub-bias wiring 40 by the bias wiring 25 in the first column and the bias wiring 25 in the third column. Similarly, in the pixel 20 (C 2), a bias voltage is applied to the pixel 20 (C 2) through the sub-bias wiring 40 by the bias wiring 25 in the first column and the bias wiring 25 in the third column.

  As described above, in the radiation detector 10 of the present embodiment, even when no voltage is applied from the bias wiring 25 due to the disconnection of the bias wiring 25, the bias adjacent in the row direction via the sub-bias wiring 40. A bias voltage is applied from the wiring 25. Specifically, a bias voltage is applied through the sub-bias wiring 40 from the bias wiring 25 that applies a bias voltage to the pixels 20 adjacent in the row direction. Therefore, charges can be output from the pixel 20 to the signal wiring 3, and a defective pixel can be prevented. Therefore, the occurrence of line defects can be suppressed.

  Next, an operation when a locally intense light (light obtained by converting radiation by a scintillator) is irradiated on the radiation detector 10 will be described. A case where intense light is irradiated on the pixel 20 (B2) locally on the conventional radiation detector 1000 shown in FIG. 11 will be described with reference to FIG. In the pixel 20 of the conventional radiation detector 1000 shown in FIGS. 11 and 12, charges (holes) generated by light irradiation are output to the signal wiring 3, and current (electron) is supplied via the bias wiring 25. ) Flows. As shown in FIG. 12, the electrons move from the pixel 20 (B2) to the pixel 20 (A2) and the pixel 20 (C2) due to the intense light irradiation to the pixel 20 (B2), so that the pixel 20 (A2) and the pixel 20 A current flows from 20 (C2) to the pixel 20 (B2). At this time, in the pixel 20 (A2) and the pixel 20 (C2), a voltage drop ΔV expressed by the following equation (1) is generated according to the amount of flowing current.

ΔV = ΔI (current value) × R (resistance value) (1)
Therefore, the voltage drop ΔV increases as the current ΔI increases. Since the current ΔI increases according to the amount of light irradiated, the current ΔI increases as the light amount increases, and the voltage drop ΔV increases.

  Further, at this time, the pixel 20 (pixel 20 (A1), 20 (A3), 20 (B1), 20 (B3), 20 (C1), 20 ( In C3)), no charge (electrons) moves from the pixel 20 (B2), so that no voltage drop occurs and the pixel 20 (B2) is in a normal state.

  In this case, line unevenness occurs in the column direction due to the difference between the normal pixel 20 and the pixel 20 where the voltage drop has occurred.

  On the other hand, the case where intense light is irradiated to the pixel 20 (B2) locally to the radiation detector 10 of this Embodiment shown in FIG.3 and FIG.8 is demonstrated with reference to FIG. In the pixel 20 of the radiation detector 10 of the present embodiment shown in FIGS. 3 and 8, charges (holes) generated by light irradiation are output to the signal wiring 3, and the bias wiring 25 and the sub-bias wiring Current (electrons) flows through 40. As shown in FIG. 8, the pixel 20 (B2) is irradiated with intense light to the pixel 20 (B2) to the pixel 20 (A2), the pixel 20 (B1), the pixel 20 (B3), and the pixel 20 (C2). , Current flows through the pixel 20 (A2), the pixel 20 (B1), the pixel 20 (B3), and the pixel 20 (C2). At this time, in the pixel 20 (A2), the pixel 20 (B1), the pixel 20 (B3), and the pixel 20 (C2), the voltage drop ΔV represented by the above equation (1) according to the flowing current amount is Occur.

  Also in the radiation detector 10 of the present embodiment, the voltage drop ΔV increases as the current ΔI increases, and the current ΔI increases and the voltage drop ΔV increases as the amount of irradiated light increases. However, in the radiation detector 10 of the present embodiment, the charges (electrons) generated in the pixel 20 (B2) are transferred to the four pixels 20 ((A2), 20 (B1), 20 (B3), and 20 (C2)). Therefore, the current ΔI per pixel 20 is smaller than the current ΔI per pixel 20 of the above-described conventional radiation detector 1000. Accordingly, the voltage drop ΔV is also reduced, and the difference from the surrounding normal pixel 20 ((A1), (A3), (C1), (C3)) is reduced, so that unevenness is reduced.

  Further, in the present embodiment, the pixels 20 in which the voltage drop ΔV occurs are linear (columnar) in the above-described conventional radiation detector 1000, but are present in an area, and thus unevenness occurs. From line shape to area shape. In general, when a user or the like visually observes, an area-like unevenness is less noticeable than a line-like unevenness. Therefore, in this embodiment, unevenness can be made inconspicuous.

  As described above, in the radiation detector 10 of the present embodiment, by providing the sub-bias wiring 40, it is possible to ensure redundancy with respect to the disconnection of the bias wiring and to suppress pixel unevenness.

  As shown in FIG. 3 and the like, in the radiation detector 10 of the present embodiment, the sub-bias wiring 40 is formed so as to intersect the signal wiring 3. Therefore, parasitic capacitance is generated by the sub-bias wiring 40 and the signal wiring 3 at this intersection. Since the parasitic capacitance increases in accordance with the area of the intersection, the width of the sub-bias wiring 40 is preferably narrower in order to suppress the parasitic capacitance. Since the sub-bias wiring 40 is for ensuring redundancy with respect to the bias wiring 25, even if it is thinner than the bias wiring 25, the effect is sufficiently exhibited. Therefore, the sub-bias wiring 40 is preferably thinner than the bias wiring 25.

  In addition, the parasitic capacitance generated by the sub-bias wiring 40 and the signal wiring 3 becomes larger as the distance between the signal wiring 3 and the sub-bias wiring 40 at the intersection is shorter. For this reason, the sub-bias wiring 40 and the signal wiring 3 are preferably formed as far as possible from each other. Therefore, in this embodiment, the interlayer insulating film 12 and the sensor unit 103 function as a planarizing layer that planarizes the step formed by the TFT switch 4 between the signal wiring 3 and the sub-bias wiring 40. An interlayer insulating film 23 that functions as a flattening layer for flattening the step is formed (see FIGS. 5 and 6). In this embodiment, by providing the interlayer insulating film 12 and the interlayer insulating film 23, at least 2 to 10 μm is provided between the sub-bias wiring 40 and the signal wiring 3, as a specific example, 4 μm (interlayer insulating film 12 = 2 μm + interlayer insulating film 23 = 2 μm). Thus, it is preferable that the distance between the sub-bias wiring 40 and the signal wiring 3 is at least 2 μm. In order to form the sub-bias wiring 40 and the signal wiring 3 as far as possible from each other, in this embodiment, the interlayer insulating film 12 and the interlayer insulating film are interposed between the signal wiring 3 and the sub-bias wiring 40 as described above. However, the present invention is not limited to this. For example, three or more planarization layers or an insulating film may be provided.

  In addition, when the sub-bias wiring 40 is provided on the TFT switch 4, parasitic capacitance is generated by the sub-bias wiring 40 and the TFT switch 4, so that the region that affects the TFT switch 4, at least above the TFT switch 4, passes. In order to avoid this, it is preferable to provide the sub-bias wiring 40.

  Note that the specific width of the sub-bias wiring 40, the distance from the signal wiring 3, and the like may be determined in consideration of the size of the pixel 20, desired image quality, the size of the parasitic capacitance to be generated, and the like.

  In the radiation detector 10 of the present embodiment, the sub-bias wiring 40 is provided for each row, and the bias wiring 25 for applying a bias voltage to all the pixels 20 is provided to the pixels 20 adjacent to both sides in the row direction. On the other hand, it is configured to be connected to the bias wiring 25 for applying a bias voltage, but the present invention is not limited to this. For example, the sub-bias wiring 40 may be provided only for some of the pixels 20, or the sub-bias wiring 40 for the pixels 20 adjacent to one side in the row direction of the pixels 20. May be provided. For example, the sub-bias wiring 40 may be provided in some rows. Further, for example, as shown in FIG. 9, the sub-bias wiring 42 may be provided so as to form a repeated pattern for each of the plurality of pixels 20 at a constant interval. With this configuration, it is possible to suppress parasitic capacitance generated by the sub-bias wiring 42 and the signal wiring 3. When the sub-bias wiring 42 is provided for each of the plurality of pixels 20 in this way, it is preferable that the wiring structure in the plan view is a pattern repetition in which the plurality of pixels 20 are formed as one pattern. Specific examples include 8 pixels × 8 pixels or 16 pixels × 16 pixels. With this configuration, the image quality is improved. In general, when the radiation detector 10 is inspected by an inspection apparatus, since inspection is performed in units of pixel groups, if a different pattern is included, a problem that a different pattern is detected as an error (defect) occurs. There is a case. As shown in FIG. 9, it is preferable to repeat the same pattern because such a problem can be avoided.

  As described above, in the radiation detector 10 according to the present embodiment shown in FIG. 3, the sub-bias wiring 40 is provided for each row of the pixels 20. Bias wirings 25 for applying a bias voltage to the pixels 20 in the row are connected to each other. As a result, even if a disconnection occurs in the bias wiring 25, the pixel 20 to which the bias voltage is no longer applied from the bias wiring 25 due to the disconnection is another bias wiring 25 that applies a bias voltage to the pixel 20 adjacent in the row direction. Since a bias voltage is applied through the sub-bias wiring 40 from the pixel 20, charges can be output from the pixel 20 to the signal wiring 3.

  Further, even when the radiation detector 10 is locally irradiated with intense light, a charge is locally generated in the pixel 20, and a current flows to the pixel 20 adjacent to the pixel 20, the same as the pixel 20 in which the charge is generated. Current flows between the pixel 20 in which charge is generated and the pixel 20 adjacent in the row direction via the sub-bias wiring 40 as well as the pixel 20 in the adjacent row connected to the bias wiring 25. Therefore, the voltage drop ΔV per pixel 20 can be suppressed. Furthermore, since the unevenness caused by the voltage drop ΔV can be made into an area shape, it is difficult to visually recognize the unevenness.

  Therefore, by providing the plurality of sub-bias wirings 40 in at least the pixel region including the plurality of pixels 20, it is possible to ensure redundancy with respect to the disconnection of the bias wiring 25 and to suppress unevenness.

  In the present embodiment, when viewed in units of one pixel, the number of sub-bias wirings 40 that connect the pixels 20 and 20 is one, but a plurality of sub-bias wirings 40 may be used. In the case where a plurality of sub-bias wirings 40 are provided for each pixel 20, redundancy against disconnection is further ensured. However, since the parasitic capacitance generated increases as the number of sub-bias wirings 40 provided increases, It may be determined from the viewpoint of ensuring the safety and the parasitic capacitance generated.

  Further, in the present embodiment, the pixels 20 and the pixels 20 in the same row in the adjacent columns are connected by the sub-bias wiring 40, but the present invention is not limited to this. You may make it connect. As a specific example, in the radiation detector 10 illustrated in FIG. 3, the pixel 20 (B2) is connected to the pixel 20 (B1) and the pixel 20 (B2) by the sub-bias wiring 40. B2) may be connected to the pixel 20 (A1), the pixel 20 (A3), the pixel 20 (C1), and the pixel 20 (C3) by the sub-bias wiring 40. In this case, the size of the intersection where the sub-bias wiring 40 intersects the signal wiring 3 and the scanning wiring 101 is larger than that when the sub-bias wiring 40 is formed as shown in FIG. The parasitic capacitance increases.

  In the present embodiment, the bias wiring 25 is formed as a line having a substantially uniform width except for the contact pad 27 portion. However, the present invention is not limited to this, and the upper surface of the pixel 20, for example, the upper electrode is formed in the pixel 20. 22 may be formed so as to cover 22. In this case as well, it is needless to say that it is preferable that the bias wiring 25 does not intersect the signal wiring 3 and the scanning wiring 101 as much as possible.

  Further, the shape of the pixel 20 is not limited to the present embodiment. For example, in the present embodiment, the rectangular pixel 20 is shown, but the shape of the pixel 20 is not limited to the rectangular shape and may be other shapes. Further, the arrangement of the pixels 20 is not limited to this embodiment as long as the signal wirings 3 are arranged according to the arrangement of the pixels 20 and the bias wiring 25 is arranged so as not to intersect the signal wiring 3. . For example, as shown in FIG. 2, the case where the pixels 20 are arranged in a matrix shape is shown as a form in which the pixels 20 are arranged in a matrix, but the pixels 20 are arranged in a two-dimensional manner. It will not be limited if it has a form arranged.

  Further, the arrangement of the signal wiring 3 and the scanning wiring 101 may be such that the signal wiring 3 is arranged in the row direction and the scanning wiring 101 is arranged in the column direction, contrary to the present embodiment.

  Moreover, in this Embodiment, you may comprise the radiation detector 10 as a flexible substrate. As the flexible substrate, it is preferable to apply a substrate using ultra-thin glass by a recently developed float method as a base material in order to improve the radiation transmittance. As for the ultra-thin glass that can be applied at this time, for example, “Asahi Glass Co., Ltd.,“ Successfully developed the world's thinnest 0.1 mm thick ultra-thin glass by the float method ”,“ online ”, Aug. 20 search], Internet <URL: http://www.agc.com/news/2011/0516.pdf> ”.

  Further, although the case of the indirect conversion method has been described in this embodiment mode, the present invention is not limited to this, and the present invention may be applied to the case of a direct conversion method in which radiation is directly converted into charges in a semiconductor layer and stored. In this case, the radiation detection element in the direct conversion method generates charges when irradiated with radiation.

  The configurations and operations of the radiographic imaging device 100 and the radiation detector 10 described in the present embodiment are merely examples, and can be changed depending on the situation without departing from the gist of the present invention. Needless to say.

  Moreover, in this Embodiment, the radiation of this invention is not specifically limited, X-ray, a gamma ray, etc. can be applied.

3 Signal wiring 4 TFT switch 10 Radiation detector 20 Pixel 25 Bias wiring 40, 42 Sub-bias wiring 100 Radiation imaging apparatus 200 Radiation imaging system

Claims (11)

A plurality of sensors arranged in a matrix, each of which includes a sensor unit that generates a charge corresponding to the dose of irradiated radiation, and a switching element that reads the charge from the sensor unit and outputs an electrical signal corresponding to the charge. Pixels,
A plurality of signal wirings provided for each column or row of the plurality of pixels and from which the electrical signal is output;
Provided for each of the plurality of pixels that output the electrical signal to the same signal wiring so as not to cross the signal wiring, and a bias voltage applied from a bias power source is applied to each column or row of the plurality of pixels. A plurality of first bias wirings supplied to the sensor units of the plurality of pixels;
A second bias wiring that is provided in a plurality of pixel regions including the plurality of pixels and that connects the first bias wirings disposed adjacent to each other;
Radiation detector equipped with.   The radiation detector according to claim 1, wherein the second bias wiring is thinner than the first bias wiring.   The radiation detector according to claim 1, wherein the second bias wiring is made of a transparent conductor.   The radiation detector according to claim 3, wherein the first bias wiring is made of a transparent conductor.   The pixel, the signal wiring, the first bias wiring, and the second bias wiring are formed by a stacked structure in which a layer including a metal layer or a conductive layer is stacked on a substrate, and the second bias wiring is The radiation detector according to any one of claims 1 to 4, wherein the radiation detector is formed of a conductive layer laminated at a position farther from the substrate than a layer including a metal layer.   Each of the pixels includes the switching element stacked on a substrate, and the sensor unit stacked on a first planarization layer that planarizes a step formed by the switching element, and the signal wiring layer and The second flattening layer for flattening the step formed by at least the first flattening layer and the sensor unit is provided between the second bias wiring layer and the second bias wiring layer. The radiation detector according to claim 5.   The pixel, the signal wiring, the first bias wiring, and the second bias wiring are formed in a stacked structure in which each layer is stacked on a substrate, and the signal wiring layer and the second bias wiring The radiation detector according to any one of claims 1 to 6, wherein the layer is provided 2 μm or more apart in the stacking direction.   The radiation detector according to any one of claims 1 to 7, wherein the second bias wiring is provided in a region other than the region where the switching element is provided.   The radiation detector according to any one of claims 1 to 8, wherein the second bias wiring is provided at a constant period with respect to the plurality of pixels. The radiation detector according to any one of claims 1 to 9, and
An imaging unit that captures a radiographic image by outputting an electrical signal from a pixel of the radiation detector to a signal wiring and generating a radiographic image according to the electrical signal;
A radiographic imaging apparatus comprising: A radiation irradiation device;
The radiographic image capturing apparatus according to claim 10, wherein a radiographic image is captured by radiation irradiated from the radiation irradiating apparatus;
Radiographic imaging system equipped with.

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