JP2008157717A - Radiation detector and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray detector 1 capable of preventing deterioration in the characteristics of a scintillator layer 31 and improving the reliability. <P>SOLUTION: A protective layer 41 for sealing the scintillator layer 31 is provided with a layered structure of films 42, constituted of a continuous polymer of organic matter, and an inorganic layer 43. The films 42 is constituted of a continuous polymer of organic matter form, the continuous coatings of which only a small amount permeates the inside of the scintillator layer 31, for improving the characteristics degradation of a scintillator layer 31. The inorganic layer 43, constituting the protective layer 41, prevents moisture permeation to the scintillator layer 31 and improves the moisture-proof property of the scintillator layer 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an indirect radiation detector and a manufacturing method thereof.

  As a new-generation X-ray diagnostic image detector, a planar X-ray detector using an active matrix or a solid-state imaging device (CCD, CMOS, etc.) is attracting attention. By irradiating the X-ray detector with X-rays, an X-ray image or a real-time X-ray image is output as a digital signal. Since this X-ray detector is a solid state detector, it is highly expected in terms of image quality performance and stability, and a lot of research and development is being conducted.

  The main application of an X-ray detector using an active matrix has been developed for breast imaging or general imaging for collecting still images with a relatively large dose, and has been commercialized in recent years. Commercialization is expected in the near future for applications in the fields of circulatory organs and digestive organs that require higher performance and real-time moving images of 30 frames per second under fluoroscopic dose. For this video application, improvement of S / N, real-time processing technology of minute signals, and the like are important development items.

  The main applications of X-ray detectors using solid-state imaging devices (CCD, CMOS, etc.) are industrial nondestructive inspections that collect still images with large doses, and still images that are inserted into the oral cavity. In recent years, dentistry and other products have been commercialized, but it is important to improve S / N, real-time processing of minute signals, miniaturization of X-ray detectors, improvement of reliability, including support for video applications. It is a development item.

  X-ray detectors are roughly classified into two methods, a direct method and an indirect method. The direct method is a method in which X-rays are directly converted into charge signals by a photoconductive film such as a-Se and led to a charge storage capacitor, and the photoconductive charges generated by the X-rays are directly stored by a high electric field. Therefore, the resolution characteristic defined by the pixel electrode pitch of the active matrix can be obtained. On the other hand, the indirect method is a method in which X-rays are once converted into visible light by the scintillator layer, and the visible light is converted into signal charges by an a-Si photodiode, CCD, CMOS, etc., and led to the charge storage capacitor. Resolution characteristics deteriorate due to optical diffusion and scattering until visible light from the scintillator layer reaches the photodiode, CCD, and CMOS.

  Usually, in an indirect X-ray detector using an active matrix, the characteristics of the scintillator layer are important because of the structure. In order to improve the output signal intensity for incident X-rays, for example, the scintillator layer has CsI or the like. High-intensity fluorescent materials composed of halogen compounds and oxide compounds such as GOS are often used. In general, a high-density scintillator layer is uniformly formed on a substrate on which one or a plurality of pixel electrodes and photoelectric conversion elements are formed by a vapor deposition method such as a vacuum deposition method, a sputtering method, or a CVD method. There are many cases. In particular, when a halogen compound such as CsI is used for the scintillator layer, resolution characteristics are often improved by forming the scintillator layer having a strip-like columnar crystal structure using a vacuum deposition method.

When a scintillator layer of a halogen compound such as CsI having a strip-like columnar crystal structure is formed, the reactivity of the halogen element such as iodine is high, and the scintillator layer is deliquescent by reacting with moisture in the atmosphere. Therefore, it is necessary to form a protective layer that blocks the scintillator layer from outside air or the like. Since the protective layer requires a continuous film formation, an organic film such as polyparaxylylene formed by hot melt molding, coating method, CVD method or the like is often used (for example, patents) Reference 1).
JP 2006-78471 A (page 8, FIG. 1-2)

  However, when a protective layer of an organic film formed by hot melt molding, coating method, CVD method or the like is formed on a scintillator layer of a halogen compound such as CsI having a strip-like columnar crystal structure, the inside of the scintillator layer Since the protective layer is impregnated in the scintillator layer, optical scattering within the scintillator layer increases, resulting in deterioration of characteristics such as sensitivity characteristics and resolution characteristics, and since the protective layer is an organic film, At the same time, moisture permeation occurs, which causes a problem in the reliability of the scintillator layer.

  The present invention has been made in view of these points, and an object of the present invention is to provide a radiation detector capable of preventing deterioration of characteristics of a scintillator layer and improving reliability and a method of manufacturing the same.

  The radiation detector of the present invention comprises a photoelectric conversion substrate that converts light into an electrical signal, a scintillator layer that is formed on the photoelectric conversion substrate and converts radiation incident from the outside into light, and a continuous polymer of organic matter. And a protective layer for sealing at least the scintillator layer.

  The manufacturing method of the radiation detector of the present invention is a manufacturing method of a radiation detector that forms a protective layer that seals at least the scintillator layer on the photoelectric conversion substrate, and includes a film made of a continuous polymer of organic matter. A protective layer comprising a step of forming by a vacuum laminating method and a step of forming an inorganic layer by a vapor phase growth method, and comprising a laminated structure of a film composed of a continuous polymer of these organic substances and an inorganic layer. , At least the scintillator layer is hermetically sealed.

  According to the present invention, the protective layer for sealing the scintillator layer has a laminated structure of a film composed of an organic continuous polymer and an inorganic layer, so that the scintillator layer is continuously impregnated with the protective layer. Since the film can be formed smoothly, the deterioration of the characteristics of the scintillator layer can be improved, and further, the inorganic layer constituting the protective layer prevents moisture permeation to the scintillator layer and the moisture resistance of the scintillator layer is improved. The reliability of the scintillator layer can also be improved.

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

  1 to 6 show a first embodiment.

  1 to 3, reference numeral 1 denotes an X-ray detector as a radiation detector. The X-ray detector 1 is an indirect X-ray planar image detector. The X-ray detector 1 includes a photoelectric conversion substrate 2 that is an active matrix photoelectric conversion substrate that converts visible light into an electrical signal.

  The photoelectric conversion substrate 2 includes a support substrate 3 as an insulating substrate formed of a rectangular flat plate-shaped glass having translucency. On the surface of the support substrate 3, a plurality of pixels 4 are two-dimensionally arranged in a matrix and spaced from each other. For each pixel 4, a thin film transistor (TFT) 5 as a switching element and a charge storage capacitor 6. A pixel electrode 7 and a photoelectric conversion element 8 such as a photodiode are formed.

  As shown in FIG. 3, on the support substrate 3, control electrodes 11 are wired as a plurality of control lines along the row direction of the support substrate 3. The plurality of control electrodes 11 are located between the respective pixels 4 on the support substrate 3 and are separated from each other in the column direction of the support substrate 3. These control electrodes 11 are electrically connected to the gate electrode 12 of the thin film transistor 5.

  On the support substrate 3, a plurality of readout electrodes 13 are wired along the column direction of the support substrate 3. The plurality of readout electrodes 13 are located between the respective pixels 4 on the support substrate 3 and are separated from each other in the row direction of the support substrate 3. The source electrode 14 of the thin film transistor 5 is electrically connected to the plurality of readout electrodes 13. The drain electrode 15 of the thin film transistor 5 is electrically connected to the charge storage capacitor 6 and the pixel electrode 7, respectively.

  As shown in FIG. 1, the gate electrode 12 of the thin film transistor 5 is formed in an island shape on the support substrate 3. An insulating film 21 is laminated on the support substrate 3 including the gate electrode 12. This insulating film 21 covers each gate electrode 12. On the insulating film 21, a plurality of island-shaped semi-insulating films 22 are laminated. These semi-insulating films 22 are made of a semiconductor and function as a channel region of the thin film transistor 5. Each of these semi-insulating films 22 is disposed to face each gate electrode 12 and covers each gate electrode 12. That is, each of these semi-insulating films 22 is provided on each gate electrode 12 via the insulating film 21.

  On the insulating film 21 including the semi-insulating film 22, island-shaped source electrodes 14 and drain electrodes 15 are formed, respectively. The source electrode 14 and the drain electrode 15 are insulated from each other and are not electrically connected. The source electrode 14 and the drain electrode 15 are provided on both sides of the gate electrode 12, and one end portions of the source electrode 14 and the drain electrode 15 are stacked on the semi-insulating film 22.

  As shown in FIG. 3, the gate electrode 12 of each thin film transistor 5 is electrically connected to a common control electrode 11 together with the gate electrodes 12 of other thin film transistors 5 located in the same row. Further, the source electrode 14 of each thin film transistor 5 is electrically connected to the common readout electrode 13 together with the source electrodes 14 of other thin film transistors 5 located in the same column.

  As shown in FIG. 1, the charge storage capacitor 6 includes an island-shaped lower electrode 23 formed on the support substrate 3. An insulating film 21 is laminated on the support substrate 3 including the lower electrode 23. The insulating film 21 extends from the gate electrode 12 of each thin film transistor 5 to the lower electrode 23. Further, an island-shaped upper electrode 24 is laminated on the insulating film 21. The upper electrode 24 is disposed to face the lower electrode 23 and covers each lower electrode 23. That is, each upper electrode 24 is provided on each lower electrode 23 via the insulating film 21. A drain electrode 15 is laminated on the insulating film 21 including the upper electrode 24. The other end of the drain electrode 15 is stacked on the upper electrode 24 and is electrically connected to the upper electrode 24.

On the insulating film 21 including the semi-insulating film 22, the source electrode 14 and the drain electrode 15 of each thin film transistor 5 and the upper electrode 24 of each charge storage capacitor 6, an insulating layer 25 is laminated and formed. Yes. The insulating layer 25 is made of silicon oxide (SiO ₂ ) or the like, and is formed so as to surround each pixel electrode 7.

  A part of the insulating layer 25 is formed with a through hole 26 as a contact hole communicating with the drain electrode 15 of the thin film transistor 5. On the insulating layer 25 including the through hole 26, an island-shaped pixel electrode 7 is laminated. The pixel electrode 7 is electrically connected to the drain electrode 15 of the thin film transistor 5 through the through hole 26.

  On each pixel electrode 7, a photoelectric conversion element 8 such as a photodiode for converting visible light into an electric signal is laminated.

  As shown in FIGS. 1 and 2, a scintillator layer 31 that converts X-rays as radiation into visible light is formed on the surface of the photoelectric conversion substrate 2 on which the photoelectric conversion elements 8 are formed. The scintillator layer 31 is formed by vapor deposition methods such as vacuum deposition, sputtering, and CVD, and is a high-luminance fluorescent material such as a halogen compound such as cesium iodide (CsI) or an oxide such as gadolinium sulfate (GOS). A phosphor such as a system compound is deposited on the photoelectric conversion substrate 2 in a columnar shape to form a film. The scintillator layer 31 is formed in a columnar crystal structure in which a plurality of strip-shaped columnar crystals 32 are formed in the surface direction of the photoelectric conversion substrate 2.

  A protective layer 41 that seals the scintillator layer 31 is laminated on the scintillator layer 31. The protective layer 41 has a laminated structure of a two-layer film 42 made of a continuous polymer of organic matter and an inorganic layer 43 interposed between the two layers of film 42.

  Film 42 is at least a thermoplastic resin or a thermosetting phenol resin, amino resin, unsaturated polyester, epoxy resin, allyl resin, silicone, polyurethane, polyethylene, polypropylene, polymethylpentene, polybutene, polystyrene, polybutadiene, styrene butadiene. Resin, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polyvinylidene chloride, polytetrafluoroethylene, ethylene polytetrafluoroethylene copolymer, ethylene vinyl acetate copolymer, AS resin, ABS resin, ionomer, AAS resin, ACS resin, polyacetal, polyamide, polycarbonate, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyarylate, polysulfone, poly Polyether sulfone, polyimide, polyamideimide, polyphenylene sulfide, cellulose acetate, celluloid, one of the cellophane as the main component, is formed by crimping or heat bonding by a vacuum laminating method.

The inorganic layer 43 includes at least a metal including Al, Ti, Ni, Cu, Mo, Pd, Ag, Ta, W, Pt, and Au, an oxide including SiO ₂ , Al ₂ O ₃ , and TiO ₂ , Si ₃ N _4. It is formed by vapor phase epitaxy mainly composed of any one of nitride containing AlN, carbide containing DLC and SiC. The formation region of the inorganic layer 43 is formed larger than the formation region of the film 42.

  A lattice-shaped X-ray grid 46 that shields between the pixels 4 is formed on the protective layer 41.

  Next, the operation of the present embodiment will be described.

  First, X-rays 51 incident on the scintillator layer 31 of the X-ray detector 1 are converted into visible light 52 by the columnar crystals 32 of the scintillator layer 31.

  The visible light 52 reaches the photoelectric conversion element 8 of the photoelectric conversion substrate 2 through the columnar crystal 32 and is converted into an electric signal. The electric signal converted by the photoelectric conversion element 8 flows to the pixel electrode 7 and is transferred to the charge storage capacitor 6 connected to the pixel electrode 7 until the gate electrode 12 of the thin film transistor 5 connected to the pixel electrode 7 is driven. Move and hold and accumulate.

  At this time, when one of the control electrodes 11 is in a driving state, the thin film transistors 5 in one row connected to the control electrode 11 in the driving state are in a driving state.

  Then, an electrical signal stored in the charge storage capacitor 6 connected to each thin film transistor 5 in this driving state is output to the readout electrode 13.

  As a result, since signals corresponding to the pixels 4 in a specific row of the X-ray image are output, signals corresponding to the pixels 4 of all X-ray images can be output by the drive control of the control electrode 11, and this output signal Is converted into a digital image signal.

  Next, a method for manufacturing the X-ray detector 1 will be described with reference to FIG.

  As shown in FIGS. 4A and 4B, a scintillator layer 31 having a columnar crystal structure having a plurality of strip-shaped columnar crystals 32 in the surface direction of the photoelectric conversion substrate 2 is formed on the photoelectric conversion substrate 2.

  As shown in FIG. 4C, the first film 42 is formed by pressure bonding or thermocompression bonding by a vacuum laminating method so as to seal the scintillator layer 31 on the photoelectric conversion substrate 2.

  As shown in FIG. 4D, the inorganic layer 43 is formed by vapor phase growth so as to completely cover the entire film 42 of the first layer, that is, in a region wider than the region where the film 42 is formed.

  As shown in FIG. 4E, a second-layer film 42 is formed by pressure bonding or thermocompression bonding by a vacuum laminating method so as to cover the inorganic layer 43.

  As shown in FIG. 4F, an X-ray grid 46 is formed on the second-layer film 42.

  Next, a general vacuum laminating method will be described with reference to FIG.

  As shown in FIG. 5 (a), for example, a case is assumed where a film 42 is laminated on a structure 63 having large and small recesses 61 and 62 having different aspect ratios on the surface by a vacuum laminating method.

  As shown in FIG. 5 (b), a manufacturing apparatus 65 that employs a vacuum laminating method has a lower mold 66 and an upper mold 67, and a heating plate 68 for heating the structure 63 is disposed on the lower mold 66. The upper die 67 is provided with a diaphragm 69 and a heating plate 70 for heating the diaphragm 69.

  Then, a structure 63 in which the film 42 is set is disposed on the heating plate 68 of the lower mold 66.

  As shown in FIG. 5 (c), the lower die 66 and the upper die 67 are closed, the diaphragm 69 is sucked out from the lower die 66 side, and the compressed air is sent from the upper die 67 to the diaphragm. The film 42 is pressed against the structure 63 with the diaphragm 69 while the structure 69, the film 42, the diaphragm 69, and the like in the mold are heated with the heating plates 68 and 70.

  FIG. 5 (d) shows a structure 63 in which films 42 are formed by vacuum lamination. The film 42 composed of a continuous polymer of an organic substance is impregnated into a concave portion 61 having a wide opening width and a small aspect ratio along the surface shape of the structure 63, and press-bonding, for example, through holes on the photoelectric conversion substrate 2 The recess 62 having a narrow opening width such as 26 and a large aspect ratio is not impregnated.

  For this reason, as shown in FIG. 1, the film 42 composed of a continuous polymer of an organic substance is pressure-bonded or thermocompression-bonded on a scintillator layer 31 having a strip-like columnar crystal structure by a vacuum laminating method. Thus, it is possible to form a continuous film with little impregnation of the film 42 composed of a continuous polymer of an organic substance into the inside of the film, and thus it is possible to prevent deterioration of image characteristics such as sensitivity characteristics and resolution characteristics.

  Further, since the protective layer 41 is a laminated structure of the film 42 and the inorganic layer 43 made of a continuous polymer of organic matter, the inorganic layer 43 prevents moisture permeation to the scintillator layer 31, The moisture resistance of the protective layer 41 is improved, and the reliability of the scintillator layer 31 can be improved.

  Furthermore, by increasing the formation region of the inorganic layer 43 than the formation region of the film 42 composed of a continuous polymer of an organic substance when forming the protective layer 41, the moisture resistance at the end of the protective layer 41 is also improved. This greatly improves the reliability of the scintillator layer 31.

  In addition, when a metal material is selected for the inorganic layer 43 that forms the protective layer 41, in addition to the effect of preventing moisture permeation to the scintillator layer 31, functions as a reflective layer and an electromagnetic wave shield can be added. .

  And about the structure of the X-ray detector 1 of a present Example, and the structure of the X-ray detector of a prior art example, the penetration amount of the protective layer into the inside of the scintillator layer 31, and the characteristic change after formation of a protective layer are shown. The experimental results are shown in FIG. Note that the characteristic evaluation condition is the same condition, and the characteristic deterioration amount is a change amount before the protective layer is formed.

In the configuration of the X-ray detector 1 of the present embodiment, the scintillator layer 31 has a high-intensity fluorescent material: CsI (Tl Dope), the film thickness of the scintillator layer 31: 600 μm, the formation method of the scintillator layer 31: vacuum deposition method, Material of the film 42: polyimide-based laminate resin, film thickness of the film 42 of the protective layer 41: 100 μm, method of forming the film 42 of the protective layer 41: vacuum lamination method, material of the inorganic layer 43 of the protective layer 41: SiO ₂ , protection The thickness of the inorganic layer 43 of the layer 41 is 1 μm, and the formation method of the inorganic layer 43 of the protective layer 41 is a sputtering method.

  The configuration of the X-ray detector of the conventional example is the same as the configuration of the X-ray detector 1 of the present embodiment except for the protective layer 41, and the protective layer is made of material: polyparaxylylene, film thickness: 20 μm, forming method: thermal CVD method.

  Compared with the conventional example, the X-ray detector 1 of this example has less impregnation of the protective layer 41 into the scintillator layer 31 and can improve both the sensitivity deterioration amount and the resolution (MTF) deterioration amount.

  This is because the protective layer 41 that seals the scintillator layer 31 has a laminated structure of a film 42 composed of an organic continuous polymer and an inorganic layer 43, so that the protective layer 41 is impregnated inside the scintillator layer 31. Since it is possible to form a small continuous film, it is possible to improve deterioration of image characteristics such as sensitivity characteristics and resolution characteristics.

  Furthermore, since the inorganic layer 43 constituting the protective layer 41 prevents moisture permeation to the scintillator layer 31 and the moisture resistance of the scintillator layer 31 is improved, the reliability of the scintillator layer 31 can also be improved.

  As shown in the second embodiment in FIG. 7, the film 42 of the protective layer 41 may be only one layer on the side in contact with the scintillator layer 31.

  Further, as shown in the third embodiment of FIG. 8, a reflection layer 81 is formed on the scintillator layer 31 to increase the use efficiency of visible light converted by the scintillator layer 31, and the scintillator layer 31 and The reflective layer 81 may be sealed to form the film 42 and the inorganic layer 43 of the protective layer 41.

  Although the X-ray detector 1 for detecting the X-ray 51 has been described, the present invention can be similarly applied to a radiation detector for detecting other radiation.

It is a partial sectional view of a radiation detector which shows a 1st embodiment of the present invention. It is sectional drawing of a radiation detector same as the above. It is a front view which shows a radiation detector same as the above. It is explanatory drawing which shows the manufacturing method of a radiation detector same as the above in order of (a)-(f). It is explanatory drawing which shows the formation method of the film of a radiation detector same as the above in order of (a)-(d). It is a table | surface which shows the amount of impregnations of the protective layer in the inside of a scintillator layer, and the characteristic change after formation of a protective layer in a radiation detector same as the above and a prior art example. It is sectional drawing of the radiation detector which shows the 2nd Embodiment of this invention. It is sectional drawing of the radiation detector which shows the 3rd Embodiment of this invention.

Explanation of symbols

1 X-ray detector as a radiation detector 2 Photoelectric conversion substrate
31 Scintillator layer
41 Protective layer
42 films
43 Inorganic layer

Claims (5)

A photoelectric conversion substrate that converts light into an electrical signal;
A scintillator layer that is formed on the photoelectric conversion substrate and converts radiation incident from the outside into light;
A radiation detector comprising a laminated structure of a film composed of a continuous polymer of an organic substance and an inorganic layer, and comprising at least a protective layer for sealing the scintillator layer. A film composed of a continuous organic polymer that forms a protective layer is at least a thermoplastic resin or thermosetting phenol resin, amino resin, unsaturated polyester, epoxy resin, allyl resin, silicone, polyurethane, polyethylene, polypropylene. , Polymethylpentene, polybutene, polystyrene, polybutadiene, styrene butadiene resin, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polyvinylidene chloride, polytetrafluoroethylene, ethylene polytetrafluoroethylene copolymer, ethylene vinyl acetate copolymer Coalescence, AS resin, ABS resin, ionomer, AAS resin, ACS resin, polyacetal, polyamide, polycarbonate, polyphenylene oxide, polyethylene terephthalate, polybutylene Phthalate, polyarylate, polysulfone, polyether sulfone, polyimide, polyamideimide, polyphenylene sulfide, cellulose acetate, celluloid, radiation detector according to claim 1, characterized in that a main component one of cellophane. The inorganic layer forming the protective layer is at least a metal containing Al, Ti, Ni, Cu, Mo, Pd, Ag, Ta, W, Pt, Au, an oxide containing SiO ₂ , Al ₂ O ₃ , TiO _{2 3.} The radiation detector according to claim 1, wherein the main component is any one of Si ₃ N ₄ , nitride containing AlN, DLC, and carbide containing SiC. The radiation detector according to any one of claims 1 to 3, wherein the scintillator layer is made of a high-intensity fluorescent material containing at least a halogen compound. A method of manufacturing a radiation detector for forming a protective layer that seals at least a scintillator layer on a photoelectric conversion substrate,
Forming a film composed of an organic continuous polymer by a vacuum laminating method;
Forming an inorganic layer by a vapor phase growth method,
A method for producing a radiation detector, comprising: sealing a scintillator layer at least with a protective layer composed of a laminated structure of a film composed of a continuous polymer of these organic substances and an inorganic layer.

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