JP4768978B2 - Radiation detector - Google Patents

Description

  The present invention relates to a radiation detection technique, and more particularly to a radiation detector having a large area two-dimensional detection surface.

  A radiation detector such as an X-ray CT or an X-ray FPD (Flat Panel Detector) is generally an indirect detection type sensor constituted by a combination of a scintillator that converts X-rays into light and an optical sensor such as a photodiode. In a solid-state detector for X-ray CT, the photodiode array is usually fabricated on a crystalline silicon substrate. In the X-ray FPD, the photodiode array is manufactured using polysilicon, amorphous silicon, or the like in order to increase the area. These photodiode substrates are usually limited in the size that can be produced due to limitations due to the substrate material itself and the manufacturing equipment. For this reason, in order to create a radiation detector with a large area, a method of increasing the area by arranging a plurality of photodiode substrates (hereinafter referred to as tiling) has been devised.

  As a conventional example of increasing the area of an X-ray CT detector, as proposed in Japanese Patent Laid-Open No. 11-311673, a plurality of photodiode substrates are tiled to increase the number of detectors. In this conventional example, the photodiode substrates are electrically connected by wire bonding.

  As a conventional example of increasing the area of an X-ray FPD, as proposed in Japanese Patent Laid-Open No. 2000-278605, the sensor area is increased by tiling a plurality of imaging sensors. Each imaging sensor is electrically connected with a conductive substance.

  As another example of the radiation detector, there is a direct detection type sensor that detects an X-ray directly converted into an electric signal by a photoconductor.

JP-A-11-311673 JP 2000-278605 A

  In the indirect detection type sensor, a CMOS switch, a TFT switch, or the like is provided for each element (corresponding to a pixel) of the optical sensor array. In addition, an address line for selecting a pixel position by the switch and a data line for reading a signal charge detected in each pixel are provided. In the above-described conventional example, the sensor area is expanded by tiling a plurality of blocks of image sensors, but it is necessary to connect a large number of the address lines and data lines between the image sensors. For this reason, when the above-described connection is performed by conventional wire bonding, there is a problem that the number of work steps for the connection increases and the manufacturing cost increases. The minimum distance that can be connected by wire bonding is usually about 50 [μm], and it is difficult to further reduce the distance between the sensor blocks. Therefore, there is a problem that a gap that cannot be sensed (hereinafter referred to as an insensitive area) is formed between the sensor blocks.

An object of the present invention is to provide a radiation detector having a small dead area, a large area, and a low cost.
Details of the objects and novel features of the present invention will become apparent from the description of this specification and attached drawings.

  In order to achieve the above object, the radiation detector of the present invention has the following characteristics.

  (1) A photoconductor substrate that converts radiation into an electrical signal, a plurality of pixel electrodes formed on the photoconductor substrate, and a switch that selects a pixel that reads the electrical signal from the plurality of pixel electrodes A switch substrate, and a signal readout circuit for reading out the electrical signal output through the pixel electrode selected by the switch substrate, the switch substrate comprising a plurality of divided substrates, and the photoconductor The substrate is disposed in common on the front surface of at least two of the plurality of divided substrates, and the plurality of divided substrates are electrically connected to each other by connection electrodes formed on the photoconductor substrate. It is connected.

  As a result, the divided substrates can be easily connected to each other, so that the number of work steps for manufacturing the detector can be greatly reduced and the cost can be reduced. Further, since wire bonding is not required, a direct detection sensor with a small dead area can be provided by reducing the distance between the divided substrates.

  (2) In the radiation detector of (1), an insulating layer is provided between the connection electrode and the photoconductor substrate.

  Thereby, it is possible to prevent the signal charge generated in the photoconductor substrate from flowing into the connection electrode.

  (3) In the radiation detector of (2), a part or all of the connection electrode is formed on the pixel electrode with the insulating layer interposed therebetween.

  Thereby, the connection electrode can be formed without reducing the size of the pixel electrode.

  (4) In the radiation detector having the above-described configuration, the plurality of divided substrates read a pixel selection line for selecting the position of the pixel electrode and a signal read for reading the electric signal through the selected pixel electrode. The pixel selection line connecting electrode for electrically connecting the pixel selection lines extending between the plurality of divided substrates, and the signal readout extending between the plurality of divided substrates. And a signal readout line connection electrode for electrically connecting the use lines.

  Thereby, the pixel selection line and the signal readout line can be connected simultaneously between the divided substrates.

  (5) In the radiation detector having the above-described configuration, the switch substrate includes a capacitor for storing the electrical signal and a bias electrode for applying a bias voltage to the capacitor, and the connection electrode includes the connection electrode, A bias electrode connection electrode for electrically connecting the bias electrodes across a plurality of divided substrates is provided.

  As a result, the bias electrode can be shared between the divided substrates, so that the bias voltage deviation between the divided substrates can be reduced.

  (6) In the radiation detector having the above-described configuration, the photoconductor substrate includes a plurality of substrates.

  Thereby, even when it is difficult to produce a photoconductor substrate having a large area, the detector can have a large area.

  ADVANTAGE OF THE INVENTION According to this invention, the radiation detector of a large area with a small insensitive area | region with respect to a radiation can be provided at low cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a radiation detector according to an embodiment of the present invention. The radiation detector according to the present embodiment includes a mounting substrate 1, a switch array substrate 2, a photoconductor substrate 3, a gate driver 4, a common electrode 5, a signal readout circuit 6, a frame memory 10, an imaging control unit 11, and imaging condition setting. It comprises means 12, image display means 13, and the like. For the sake of explanation, FIG. 2 shows a portion excluding the common electrode 5 in FIG.

  In FIG. 1, 3 × 3 switch array substrates 2 are arranged adjacent to each other on the upper surface of the mounting substrate 1. Further, the three gate drivers 4 are arranged substantially parallel to face the three substrates forming one side of the switch array substrate 2. The three signal readout circuits 6 are arranged substantially in parallel to face the three substrates forming the other side of the switch array substrate 2. As will be described later, the gate driver 4 and the switch array substrate 2 and the signal readout circuit 6 and the switch array substrate 2 are electrically connected by bonding wires 7 (see FIG. 4 described later). On the upper surface of the switch array substrate 2, 8 × 8 photoconductor substrates 3 are arranged adjacent to each other.

The switch array substrate 2 is made of crystalline silicon, and as shown in FIG. 4 described later, readout electrodes 40, CMOS switches 42, and the like are formed in a matrix on the substrate. However, the configuration of the switch array substrate 2 is not limited to the above example. For example, an array of TFT switches formed on a glass substrate may be used instead. The gate driver 4 is a known circuit for applying a voltage to the gate of the switch, and controls the reading position in the row direction of the switch array. The signal reading circuit 6 is a known circuit for reading a signal read through the CMOS switch 42 and converting it into a digital signal. The material of the photoconductor substrate 3 is crystalline but CdTe material is used is not limited thereto, for example, it may be substituted by a known photoconductive materials such as Se and HgI _2, PbI _2. Further, Pt is used as the material of the common electrode 5, but other metal may be used instead. A DC voltage is applied to the common electrode 5 using a high voltage source (not shown). A typical example of the voltage applied at this time is 250 [V].

  Typical examples of pitch intervals and matrix sizes of the CMOS switches 42 formed in a matrix on each switch array substrate 2 are 170 [μm] and 900 × 900 pixels, respectively. Therefore, one side of the entire switch array substrate 2 is 45.9 [cm], and a matrix of 2700 × 2700 pixels is formed. On the other hand, the size of one side of the photoconductor substrate 3 is 5.1 [cm], which corresponds to the size of 300 pixels. Therefore, one side of the entire photoconductor substrate 3 is 40.8 [cm], and radiation can be detected within a matrix of 2400 × 2400 pixels. A typical example of the thickness of the photoconductor substrate 3 is 500 [μm].

  Next, the operation of the radiation detector according to the present embodiment will be described. When radiation is input to the photoconductive band substrate 3 and its energy is absorbed, a pair of electrons and holes (hereinafter referred to as carriers) is generated inside the photoconductive substrate 3. These carriers are read out through a pixel electrode 52 shown in FIG. 5 to be described later by an electric field formed by a voltage applied to the common electrode 5, and charges are accumulated in the pixel capacitor 41. The accumulated charge is read by the signal read circuit 6 when the CMOS switch 42 is turned on, converted into a digital signal, and then recorded in the frame memory 10. The image display unit 13 displays the image information recorded in the frame memory 10. The gate driver 4 controls ON and OFF of the CMOS switch 42. The imaging control means 11 controls the timing of recording in the gate driver 4, signal readout circuit 6 and frame memory 10. The user can set various recording timings via the photographing condition setting unit 12.

  FIG. 3 is a top view of the radiation detector according to the present embodiment. As described above, the photoconductor substrate 3 is disposed in common across the boundary line of the adjacent switch array substrate 2. The common electrode 5 is disposed in common on all the photoconductor substrates 3. Below, the structure inside the area | region 300 shown in FIG. 3 and the area | region 301 is demonstrated.

  FIG. 4 is a diagram for explaining the configuration of the region 300 shown in FIG. FIG. 4 shows detailed configurations of the gate driver 4, the switch array substrate 2, and the signal readout circuit 6. The switch array substrate 2 includes a readout electrode 40, a pixel capacitor 41, a CMOS switch 42, a gate line 45, a data line 43, a bias line 44, and the like. One ends of the gate line 45 and the data line 43 are connected to the electrode 47 and the electrode 46, respectively. The gate driver 4 includes a switch 400, and one end of the switch 400 is connected to the electrode 401. The electrode 401 and the electrode 47 are connected by a known bonding wire 7. The signal readout circuit 6 is input to the A / D converter 406 via the switch array 404 constituting the amplifier 403 and the multiplexer 405. The input end of the amplifier 403 is connected to the electrode 402. The electrode 402 and the electrode 46 are connected by a known bonding wire 7.

  The charge detected by the photoconductor substrate 3 is accumulated in the pixel capacitor 41 via the readout electrode 40. The gate driver 4 turns on the CMOS switch 42 at the corresponding column position while sequentially switching the position where the switch 400 is turned on in the row direction (vertical direction). At this time, the charge accumulated in the pixel capacitor 41 is input to the amplifier 403 via the data line 43. Since the input of electric charges to the amplifier 403 is performed simultaneously in all column direction (lateral direction) positions, the multiplexer 405 sequentially switches the switches 404 in the column direction and positions of signals input to the A / D converter 406. Switch.

  FIG. 5 is a cross-sectional view of the radiation detector according to the present embodiment, and particularly shows a tomographic plane in a direction parallel to the data line 43 in FIG. In FIG. 5, the gate lines 45 are arranged in a direction perpendicular to the paper surface. A pixel electrode 52 is formed on the back surface of the photoconductor substrate 3 and is connected to the readout electrode 40 via a known conductive resin 51. Such a connection between the pixel electrode 52 and the readout electrode 40 can be realized by using a known flip chip bonding technique or the like. Carriers generated in the photoconductor substrate are collected through the pixel electrode 52 and accumulated in the pixel capacitor 41. The material of the pixel electrode 52 is In, but is not limited to this. The pixel electrode 52 is formed on the surface of the photoconductor substrate 3 using a known vapor deposition technique or sputtering technique.

  FIG. 6 is a diagram for explaining the configuration of the region 301 shown in FIG. In the region 301, the four switch array substrates 2A to 2D are adjacent to each other. In each substrate, the end portions of the data lines 43A to 43D are connected to the electrodes 61A to 61D, respectively. In each substrate, the end portions of the gate lines 45A to 45D are connected to the electrodes 62A to 62D, respectively. Further, in each substrate, the end portions of the bias lines 44A to 44D are connected to the electrodes 60A to 60D, respectively. As shown in FIG. 7 to be described later, each electrode at the end is exposed on the upper surface side of each switch array substrate 2A to 2D. The electrode at each end adjacent to the boundary between the switch array substrates 2A-2B, 2A-2C, 2C-2D, and 2B-2D is formed on the back side of the photoconductor substrate 3 shown below. The connection electrodes 70 to 72 are connected to each other.

  FIG. 7 is a diagram for explaining the positions of the electrodes formed on the back side of the photoconductor substrate 3. However, FIG. 7 shows the electrode positions as viewed from the common electrode 5 side, and is arranged so as to overlap the upper surfaces of the switch array substrates 2A to 2D shown in FIG. In addition to the pixel electrode 52, connection electrodes 70 to 72 are formed on the back side of the photoconductor substrate 3. These are arranged on the upper surface of the adjacent electrodes 60 to 62 shown in FIG. 6 and connect the electrodes. Note that the pixel electrode 52 adjacent to the connection electrodes 70 to 72 has a smaller size than the peripheral pixel electrode 52 not adjacent to the connection electrodes 70 to 72 in order to secure a space for forming the connection electrodes 70 to 72. It is formed with. An insulating film 800 is formed between the connection electrodes 70 to 72 and the photoconductor substrate 3 as shown in FIG. 8 to be described later, and carriers generated in the photoconductor substrate 3 are transferred to the connection electrodes 70 to 72. It is made not to reach.

  FIG. 8 is a cross-sectional view of the radiation detector according to the present embodiment, and particularly shows a tomographic plane at the position 700 shown in FIG. Data lines 43A and 43B in the switch array substrates 2A and 2B are connected to electrodes 61A and 62B exposed on the upper surface of the substrate at the end portions, respectively. On the other hand, a connection electrode 71 is formed on the back surface of the photoconductor substrate 3 via an insulating layer (insulating film) 800. The electrode 61A and the connection electrode 71, and the electrode 61B and the connection electrode 71 are connected via conductive resins 81A and 81B, respectively. Therefore, since the data lines 43A and 43B are electrically connected, a signal can be output through them. Although not described with reference to the drawings, the gate line 45 and the bias line 44 between adjacent switch array substrates can be connected in the same manner.

  FIG. 9 is a diagram for explaining another example of electrode positions formed on the back side of the photoconductor substrate 3. However, FIG. 9 shows the electrode position as viewed from the common electrode 5 side, and is arranged so as to overlap the upper surfaces of the switch array substrates 2A to 2D shown in FIG. Pixel electrodes 52 of equal size are formed at equal intervals on the back side of the photoconductor substrate 3. Further, the connection electrodes 90 to 92 are formed on the upper surface of the photoconductor substrate 3 and the upper surface of the pixel electrode 52 with an insulating layer (insulating film) 1000 interposed therebetween as shown in FIG. These are arranged on the upper surface of the adjacent electrodes 60 to 62 shown in FIG. 6 and connect the electrodes. As in this example, by increasing the size of the pixel electrode 52, carriers generated in the photoconductor substrate 3 can be read efficiently.

  FIG. 10 is a cross-sectional view of the radiation detector according to the present embodiment, and particularly shows a tomographic plane at the position 900 shown in FIG. Data lines 43A and 43B in the switch array substrates 2A and 2B are connected to electrodes 61A and 62B exposed on the upper surface of the substrate at the end portions, respectively. On the other hand, a connection electrode 91 is formed on the back surfaces of the photoconductor substrate 3 and the pixel electrode 52 with an insulating film 1000 interposed therebetween. The electrode 61A and the connection electrode 91, and the electrode 61B and the connection electrode 91 are connected through conductive resins 101A and 101B, respectively. Therefore, since the data lines 43A and 43B are electrically connected, a signal can be output through them. Although not described with reference to the drawings, the gate line 45 and the bias line 44 between adjacent switch array substrates can be connected in the same manner.

  Although an example of the radiation detector according to the present invention has been described above, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the scope of the invention. For example, by applying the present invention to a sensor for multi-slice X-ray CT, multilayering of X-ray CT sensors can be realized. In the above embodiment, the photoconductor substrate 3 has a large area by tiling a plurality of substrates. However, a single photoconductor substrate may be used instead. For example, a photoconductor substrate having a large area can be manufactured by using an amorphous material or the like instead of a crystal material that is difficult to increase in area.

  As described above in detail, according to the present invention, it is possible to provide a large-area radiation detector with a small area insensitive to radiation at a low cost. Further, when a large-area radiation detector is manufactured by arranging a plurality of small detectors, electrical connection between the small detectors can be performed without performing wire bonding.

The figure which shows schematic structure of the radiation detector which concerns on one Example of this invention. The figure showing the part except the common electrode 5 in FIG. The top view of the radiation detector concerning one example of the present invention. The figure for demonstrating the structure of the area | region 300 shown in FIG. Sectional drawing of the radiation detector which concerns on one Example of this invention. The figure for demonstrating the structure of the area | region 301 shown in FIG. The figure for demonstrating the position of the electrode formed in the back side of a photoconductor substrate. The figure showing the tomographic plane in the position 700 shown in FIG. The figure for demonstrating another example of the electrode position formed in the back side of a photoconductor substrate. The figure showing the tomographic plane in the position 900 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Mounting board | substrate 2, 2A-2D ... Switch array board | substrate, 3 ... Photoconductor board | substrate, 4 ... Gate driver, 5 ... Common electrode, 6 ... Signal readout circuit, 7 ... Bonding wire, 10 ... Frame memory, 11 ... Imaging control means, 12 ... Imaging condition setting means, 13 ... Image display means, 40 ... Read electrode, 41 ... Pixel capacity, 42 ... CMOS switch, 43, 43A-43D ... Data line, 44, 44A-44D ... Bias line, 45, 45A to 45D ... gate line, 46, 47 ... electrode, 51 ... conductive resin, 52 ... pixel electrode, 60A-60D, 61A-61D, 62A-62D ... electrode, 70-72 ... connection electrode, 400, 404 ... Switch, 401, 402 ... Electrode, 403 ... Amplifier, 405 ... Multiplexer, 406 ... A / D converter, 81A, 81B ... Conductivity Fat, 90 to 92 ... connection electrodes, 101A, 101B ... conductive resin, 700 ... (in Fig. 7) positions, 800: insulating film, 900 ... (in Fig. 9) position, 1000 ... insulating film.

Claims (1)

A switch having a photoconductor substrate for converting radiation into an electrical signal, a plurality of pixel electrodes formed on the photoconductor substrate, and a switch for selecting a pixel from which the electrical signal is read out of the plurality of pixel electrodes A substrate and a signal readout circuit for reading out the electrical signal output through the pixel electrode selected by the switch substrate, the switch substrate is composed of a plurality of divided substrates, and the photoconductor substrate is An insulating layer that is disposed in common on the front surface of at least two of the plurality of divided substrates, is formed on the photoconductor substrate, and has a space between the adjacent pixel electrodes. The radiation detector is characterized in that the plurality of divided substrates are electrically connected by connection electrodes formed in this manner.

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