JP2009130127A - Radiation detector and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance X-ray detector and its manufacturing method. <P>SOLUTION: The area of a transparent conductive film 39 is made larger compared with the area of an amorphous silicon film 35 and the peripheral part 39a of the transparent conductive film 39 is projected than the side surface of the amorphous silicon film 35. Electric current, necessary for the driving of a photodiode element 18, is supplied from the whole surface of the amorphous silicon film 35 to improve the responsibility of the photodiode element 18. The amount of incident fluorescent light into the amorphous silicon film 35 is increased by the transparent conductive film 39 having the function of reflection preventive film to improve the sensitivity of the photodiode element 18. Even when a high electric field necessary for the operation of the photodiode element 18 is impressed on the amorphous silicon film 35, leakage current, which flows through the side surface of the amorphous silicon film 35, is not increased and the performance of the photodiode element 18 is improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radiation detector for detecting radiation and a method for manufacturing the same.

  As a new generation diagnostic X-ray image detector, a planar X-ray detector using an active matrix has attracted 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, there are great expectations in terms of image quality performance and stability, and many researches and developments are underway.

  As the first application for practical use, it has been developed for the chest or general radiography 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 circulatory and gastrointestinal fields that require higher performance and real-time video at 30 frames per second under fluoroscopic dose. For this moving image application, improvement of S / N and real-time processing technology of minute signals are important development items.

  This type of X-ray detector can be broadly divided into two methods, a direct method and an indirect method. The direct method is a method in which X-rays are directly converted into a charge signal by a photoconductive film such as a-Se and led to a charge storage capacitor. On the other hand, in the indirect method, X-rays are received by a fluorescent conversion film that is a scintillator layer, and once converted into visible light, visible light is converted into a signal charge by an a-Si photodiode or CCD, and led to a charge storage capacitor. It is a method.

  Many of the X-ray detectors currently in practical use adopt the indirect method. In a conventional indirect X-ray detector, an X-ray image transmitted through a human body or the like is incident on the X-ray detector, and the image information is converted into an electrical signal. At this time, X-rays are converted into visible light by the fluorescence conversion film, and the visible light is detected for each pixel formed in a grid pattern on the photoelectric conversion substrate and is output as an electrical signal of two-dimensional image information.

  The photoelectric conversion substrate is a thin film transistor (TFT) panel manufacturing process that is similar to the manufacturing process of a liquid crystal display device. A circuit board on which signal wiring and thin film transistors are formed is created, and fluorescence from the input surface is detected on the circuit board. A photodiode element to be formed is formed in a lattice pattern for each pixel, and the photodiode element is electrically connected to a thin film transistor disposed below.

  Photodiode elements formed in a lattice pattern for each pixel of a photoelectric conversion substrate generally include amorphous silicon (a-Si) as a main component, and phosphorus is added to an i-type amorphous silicon layer that is an intrinsic semiconductor. The structure is sandwiched between an n-type amorphous silicon layer realized by the above and a p-type amorphous silicon layer realized by adding boron. In general, an n-type amorphous silicon layer, an i-type amorphous silicon layer, and a p-type amorphous silicon layer are sequentially stacked on a circuit board on which signal wirings and thin film transistors are formed by a CVD method (vapor phase growth method). After that, in order to avoid image resolution degradation due to charge movement in the in-plane direction inside the photodiode element, the photodiode element is separated for each pixel and electrically separated for each pixel, and then the upper part of the photodiode element Wiring for supplying a voltage to is formed (for example, see Patent Document 1).

A fluorescence conversion film on the input surface is formed on the photoelectric conversion substrate manufactured by such a process. The fluorescence conversion film is made of a fluorescent material having a function of converting incident X-rays into visible light. As the type of fluorescent material, Gd ₂ O ₂ S: Tb (terbium-added gadolinium sulfide oxide) or CsI: Tl (thallium-added iodine) is used. Cesium) is often used.

When Gd ₂ O ₂ S: Tb is used as a fluorescent material, a film in which particulate Gd ₂ O ₂ S: Tb is dispersed in a resin is used. On the other hand, when CsI: Tl is used as a fluorescent substance, a CsI: Tl film is formed on the photoelectric conversion substrate by a vacuum deposition method. By taking appropriate manufacturing conditions at that time, A CsI: Tl film having a columnar structure in the vertical direction can be formed. The CsI: Tl input surface having the columnar structure has higher resolution with respect to incident X-rays than the input surface using Gd ₂ O ₂ S: Tb, and a high-performance X-ray detector is possible.

  The photodiode element is formed on a circuit board on which a thin film transistor is formed, and the charge generated inside the photodiode element is transparent of ITO (tin-added indium oxide) formed on the photodiode element. The conductive film is taken out through the lower electrode formed between the photodiode element and the circuit board. The lower electrode is connected to the drain terminal of the thin film transistor on the circuit board, and charges are output to the outside in accordance with the driving of the thin film transistor. The lower electrode used here is usually a metal material mainly composed of aluminum, which is easy to form a thin film and has low resistivity and easy pattern formation.

  In the manufacturing process of the photodiode element mainly composed of amorphous silicon, an amorphous silicon film is laminated on the entire surface of the circuit board by CVD (scientific vapor deposition). In order to improve the performance as a photodiode, this amorphous silicon film is mainly an n-type amorphous silicon film mixed with a small amount of phosphorus, an i-type amorphous silicon film that does not step on impurities, and a p-type amorphous silicon film mainly mixed with a small amount of boron. It has a structure in which products are sequentially stacked.

  After the formation of the amorphous silicon film formed on the entire surface of the circuit board, an ITO film that is a transparent conductive film is laminated on the entire surface. The ITO film formed on the amorphous silicon film supplies current to the amorphous silicon film functioning as a PD and is generated from a phosphor such as CsI: Tl that forms the input surface by the X-rays incident on the X-ray detector. A function of transmitting light to be transmitted is necessary. At this time, the optical refractive index of the ITO film is around 1.97, and it has a function as an optical antireflection film by being laminated on an amorphous silicon film having an optical refractive index of 4.3. It becomes possible to transmit more. Specifically, by making the thickness of the ITO film around 70 nm, the reflectance near 550 nm at which light emission from the input surface constituted by CsI: Tl becomes maximum can be made almost 0%, The sensitivity of the photodiode can be increased.

  In the state of the amorphous silicon film formed on the entire surface of the circuit board, the charge generated by the input optical image spreads laterally through the inside of the amorphous silicon film, and the resolution of the image is extremely deteriorated. It is necessary to separate the amorphous silicon film including the transparent conductive film in units of pixels to prevent the charges generated by the incident light from spreading in the lateral direction.

  In order to separate the amorphous silicon film and the transparent conductive film for each pixel, a photosensitive resist film is applied on the transparent conductive film, the pixel pattern is exposed to the photosensitive resist film by ultraviolet irradiation, and development processing is performed. A separated resist pattern is formed. Thereafter, the transparent conductive film is removed from the region without the resist pattern using an etching solution mainly composed of hydrochloric acid or oxalic acid.

After the pattern formation of the transparent conductive film is completed, the step of separating the amorphous silicon film for each pixel is performed. On the amorphous silicon film, a patterned transparent conductive film and a photosensitive resist film are laminated. The amorphous silicon film in the exposed region reacts with fluorine ions and fluorine radical atoms by introducing this circuit board into a chamber in which fluorine-containing gas (CF ₄ , SF ₆ ) is made into a plasma state by high-frequency power or the like. Then, it becomes a gaseous fluorine compound and is detached from the surface of the circuit board. By this reaction, it is possible to remove all of the amorphous silicon film in a region not covered with the photosensitive resist film or the transparent conductive film, and an amorphous silicon film separated for each pixel is completed.

After the amorphous silicon film is separated for each pixel, the entire surface of the circuit board is covered with a transparent resin. A voltage is applied to each amorphous silicon film by forming a contact hole in the transparent resin on the transparent conductive film left on the amorphous silicon film and forming an upper electrode in a region including the inside of the contact hole. It becomes possible. Finally, a transparent resin is again applied and formed on the entire surface of the circuit board, thereby completing a photoelectric conversion substrate including the photodiode element and the circuit board. An X-ray detector is completed by stacking a fluorescence conversion film that emits fluorescence by X-rays on this photoelectric conversion substrate and connecting an external circuit.
JP-A-9-90048 (page 4, FIG. 1)

  In the X-ray detector manufacturing method described above, the outer dimension of the amorphous silicon film is larger than the outer dimension of the transparent conductive film. This is because when the transparent conductive film that is not covered with the patterned resist film is dissolved and removed by the wet etching process, the etching solution penetrates from the side of the transparent conductive film at the end of the resist. This is because a part of the transparent conductive film covered with the resist is removed. As a result, the outer dimension of the remaining transparent conductive film pattern is smaller than the outer dimension of the resist film pattern. In the subsequent etching of the amorphous silicon film, a dry etching process using plasma in vacuum is often used. Compared with the wet process used for etching the transparent conductive film, this process has an etching shape anisotropy that is very close to the resist film shape. Therefore, the outer dimension of the transparent conductive film to be wet etched is smaller than the outer dimension of the amorphous silicon film to be dry etched.

  As described above, the outer dimensions of the transparent conductive film are smaller than the outer dimensions of the amorphous silicon film, thereby causing the following problems.

  The transparent conductive film formed on the amorphous silicon film supplies a current to the photodiode made of amorphous silicon and also has a function as an antireflection film. In the photodiode of the conventional X-ray detector, a region not covered with the transparent conductive film is generated on the surface of the amorphous silicon film functioning as the photodiode. In the region where the amorphous silicon film is exposed, the current required for driving the photodiode is insufficiently supplied, and the response is deteriorated. In addition, since there is no transparent conductive film functioning as an antireflection film, the reflectance of fluorescence generated from the input surface increases in that region, and the amount of fluorescence incident on the amorphous silicon film decreases. As a result, the response of the photodiode deteriorates and the sensitivity decreases, and the performance as an X-ray detector deteriorates.

  In addition, when the amorphous silicon film and the transparent conductive film constituting the photodiode are identical in shape, the above problem does not occur, but a problem of increasing the leakage current of the photodiode occurs. In order to perform a favorable operation as a photodiode, it is necessary to apply a high electric field of several tens of thousands V / cm to the amorphous silicon film. In a state where light does not enter from the outside, even if such a high electric field is applied, the leakage current flowing inside the amorphous silicon film is sufficiently small, and no problem occurs in operation as an X-ray detector. However, the side surface of the amorphous silicon film is electrically unstable, and the leakage current flowing through the side surface often occupies most of the leakage current flowing through the entire photodiode. The leakage current flowing through the side surface of the amorphous silicon film is strongly influenced by the electric field strength, and the leakage current increases significantly as the electric field strength increases. In the photodiode according to the prior art, a conductive p-type amorphous silicon film and a transparent conductive film are stacked on the dielectric i-type amorphous silicon film, and the outer shape of the transparent conductive film is smaller than that of the amorphous silicon film. If a high electric field of tens of thousands of V / cm necessary for the operation of the photodiode is applied to the amorphous silicon film in this state, the electric field is concentrated on the end of the amorphous silicon film, and a large electric field strength is generated locally. Become. Due to this phenomenon, the leakage current flowing through the side surface of the amorphous silicon film constituting the photodiode is increased, so that the performance as the photodiode is deteriorated and the performance of the X-ray detector is inevitably lowered.

  This invention is made | formed in view of such a point, and it aims at providing a high performance radiation detector and its manufacturing method.

  The radiation detector of the present invention is a radiation detector in which a photoelectric conversion element and a fluorescence conversion film are formed on a circuit board, and the photoelectric conversion element includes a semiconductor layer formed on the circuit board and the semiconductor layer. The transparent conductive film is formed over the entire surface of the semiconductor layer, and the area of the transparent conductive film is larger than the area of the semiconductor layer.

  The radiation detector of the present invention is a radiation detector in which a photoelectric conversion element and a fluorescence conversion film are formed on a circuit board, and the photoelectric conversion element includes a semiconductor layer formed on the circuit board and the semiconductor The transparent conductive film is formed on the layer, the entire surface of the semiconductor layer is covered with the transparent conductive film, and the peripheral portion of the transparent conductive film protrudes from the peripheral portion of the semiconductor layer.

  In addition, the manufacturing method of the radiation detector of the present invention is a manufacturing method of a radiation detector in which a photoelectric conversion element and a fluorescence conversion film are formed on a circuit board, and a semiconductor constituting the photoelectric conversion element on the circuit board A step of laminating a layer and a transparent conductive film, a step of removing the transparent conductive film excluding the formation area of the photoelectric conversion element, and an area smaller than the area of the transparent conductive film except the formation area of the photoelectric conversion element And a step of removing the semiconductor layer.

  In addition, the manufacturing method of the radiation detector of the present invention is a manufacturing method of a radiation detector in which a photoelectric conversion element and a fluorescence conversion film are formed on a circuit board, and a semiconductor constituting the photoelectric conversion element on the circuit board A step of laminating a layer and a transparent conductive film, a step of removing the transparent conductive film excluding the formation area of the photoelectric conversion element, a formation area of the photoelectric conversion element, and a peripheral portion of the transparent conductive film being the semiconductor And a step of removing the semiconductor layer so as to protrude from the peripheral portion of the layer.

  According to the present invention, the transparent conductive film covers the entire surface of the semiconductor layer, and the area of the transparent conductive film is formed larger than the area of the semiconductor layer, or the peripheral portion of the transparent conductive film is larger than the peripheral portion of the semiconductor layer. As a result of protruding, it is possible to prevent deterioration of the responsiveness and sensitivity of the photoelectric conversion element and provide a high-performance radiation detector.

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

  FIG. 9 shows a perspective view of the exploded state of the radiation detector.

  11 is an X-ray detector as a radiation detector. This X-ray detector 11 is an indirect X-ray image detector, and includes a photoelectric conversion substrate 13 having a plurality of pixels 12 arranged in a matrix, and The photoelectric conversion substrate 13 is constituted by a fluorescence conversion film 14 which is an input surface laminated on the surface.

  The photoelectric conversion substrate 13 has a circuit substrate 17 in which a circuit layer 16 is formed on a substrate 15 mainly made of glass, and a photodiode element 18 as a photoelectric conversion element is provided on each circuit substrate 17 for each pixel. Is formed.

  When X-rays 19 as radiation enter the fluorescence conversion film 14, visible light corresponding to the two-dimensional distribution of the X-rays 19 is generated in the fluorescence conversion film 14, and the generated visible light is applied to the photodiode element 18. Incident light is converted into electric charge.

  Next, FIG. 10 shows a front view schematically showing the radiation detector.

  The thin film transistor (TFT) 21, the capacitor 22, and the photodiode element 18 are arranged in a lattice form as a set, and each set corresponds to the pixel 12 of the X-ray image. On the substrate 15, a plurality of control electrodes 23 connecting the gate electrodes of the thin film transistors 21 are arranged in the row direction, and a plurality of readout electrodes 24 connecting the drains of the thin film transistors 21 are arranged in the column direction. With such a circuit configuration, electric charges generated in each photodiode element 18 for each pixel 12 are connected to the respective capacitors 22 until the gate electrodes of the thin film transistors 21 connected thereto are turned on. When only one control electrode 23 is turned on in this state, the thin film transistors 21 in the same column connected to the control electrode 23 turned on are turned on and connected to the thin film transistors 21 through the thin film transistor 21. The charge of the capacitor 22 that has been applied flows to the readout electrode 24. As a result, image information corresponding to a specific row is output to the outside. Further, by sequentially changing the control electrode 23 to be turned on, it is possible to output the entire image information as a video signal to the outside.

  Next, FIG. 1 shows a cross-sectional view of the radiation detector, in which one pixel 12 is shown.

A gate electrode 27 of the thin film transistor 21 is formed on the substrate 15, and an insulating film 28 is formed on the substrate 15 including the gate electrode 27. A semiconductor film 29 is formed on the insulating film 28 so as to face the gate electrode 27. A source electrode 30 and a drain electrode 31 of the thin film transistor 21 are formed on the insulating film 28 including the semiconductor film 29, and silicon oxide (SiO ₂ ) or silicon nitride (SiNx) is formed on the source electrode 30 and the drain electrode 31. ) Or the like is formed. The source electrode 30 and the drain electrode 31 are made of an Al alloy film or an Al / Mo laminated film having excellent conductivity and environmental properties, and the insulating film 28 and the protective film 32 are made of silicon oxide (SiO ₂ ) or silicon nitride (SiNx). ) And other materials are used. The circuit board 17 is constituted by the substrate 15 and the thin film transistor 21 formed on the substrate 15. The manufacturing method of the circuit board 17 can be realized by the same technique as that of a general active liquid crystal display device, and the same material can be used.

  A photodiode element 18 is formed on the drain electrode 31 of the thin film transistor 21. This photodiode element 18 is an amorphous silicon film 35 as a semiconductor layer mainly composed of amorphous silicon (a-Si). The photodiode element 18 has an n-type amorphous silicon layer 36, an i-type amorphous silicon layer on the drain electrode 31 of the thin film transistor 21. 37, a p-type amorphous silicon layer 38 is sequentially stacked by the CVD method, and has a function of converting photons incident from the outside into charges. On the photodiode element 18, a transparent conductive film 39 having a function of supplying current to the photodiode element 18 and transmitting light from the outside is formed by a sputter deposition method. The photodiode element 18 and the transparent conductive film 39 have a structure separated in units of the pixels 12 of the X-ray detector 11, and by cutting off the electrical connection between the adjacent pixels 12, a high resolution X A line image can be obtained.

  The transparent conductive film 39 covers the entire surface of the amorphous silicon film 35, the area of the transparent conductive film 39 is larger than the area of the amorphous silicon film 35, and the peripheral portion 39a of the transparent conductive film 39 is the amorphous silicon film 35. It protrudes from the periphery or side.

  An insulating layer 42 made of a resin, an inorganic insulator, or the like is formed covering the thin film transistor 21, the photodiode element 18, and the transparent conductive film 39, and is electrically connected to the transparent conductive film 39 on the insulating layer 42. A bias electrode 43 made of metal is formed, and an upper protective film 44 is formed to cover the insulating layer 42 and the bias electrode 43. The photoelectric conversion substrate 13 is configured by the circuit substrate 17, the photodiode element 18 formed on the circuit substrate 17, and the like.

  Next, the manufacturing process of the photoelectric conversion substrate 13 of the X-ray detector 11 will be described.

  FIG. 2 shows a circuit board 17 manufactured by a general manufacturing process of a liquid crystal display device. On the substrate 15, a gate electrode 27, an insulating film 28, a semiconductor film 29, a source electrode 30, a drain electrode 31, and a protection A film 32 is formed.

As shown in FIG. 3, an n-type amorphous silicon layer 36, an i-type amorphous silicon layer 37, and a p-type amorphous silicon layer 38 constituting the amorphous silicon film 35 are sequentially stacked on the entire surface of the circuit substrate 17 by the CVD method. . At that time, silane (SiH ₄ ), diborane (B ₂ H ₆ ), phosphine (PH ₃ ) and the like are decomposed in a plasma state, and amorphous silicon layers 36, 37, and 38 are sequentially stacked on the substrate surface.

  After the formation of each amorphous silicon layer 36, 37, 38, a transparent conductive film 39 such as tin-doped indium oxide (ITO) or zinc-doped indium oxide (IZO) is formed on the p-type amorphous silicon layer 38 by vacuum sputter deposition. To do.

  Subsequently, as shown in FIG. 4, a photosensitive resin is applied to the surface of the transparent conductive film 39, and a lattice pattern is exposed on the photosensitive resin by an ultraviolet exposure technique. Thereafter, a pattern of the photosensitive resist film 47 is formed on the transparent conductive film 39 by performing a development process.

  Subsequently, as shown in FIG. 5, the entire substrate is placed in an etching solution containing oxalic acid or aqua regia as a main component, and exposed portions of the transparent conductive film 39 not covered with the photosensitive resist film 47 are removed. At this time, the etching solution enters from the side surface of the transparent conductive film 39 sandwiched between the amorphous silicon film 35 and the photosensitive resist film 47, and a part of the transparent conductive film 39 covered with the photosensitive resist film 47 is also removed. The Therefore, the size of the transparent conductive film 39 is smaller than the size of the photosensitive resist film 47.

Subsequently, as shown in FIG. 6, the step of removing the amorphous silicon film 35 is performed. It is known that silicon reacts with fluorine to become a highly volatile fluorine compound. The substrate shown in FIG. 6 is placed in a vacuum apparatus, and high-frequency power is input from the outside in a state where a fluorine-containing gas is allowed to flow in the vacuum apparatus, thereby generating a plasma of fluorine-containing gas around the substrate. Can do. As an example, CF ₄ (carbon tetrafluoride) is allowed to flow to a pressure of 30 mTorr as a gas type, and at the same time, a high frequency power of several hundred watts having a frequency of 13.56 MHz is applied from the outside, A plasma state can be easily obtained. At this time, the fluorine-containing gas obtains energy from the plasma and generates a large amount of excited fluorine atoms and ionic fluorine atoms. Fluorine atoms in an ionic state or an excited state easily react with silicon, become a highly volatile fluorine compound, and leave from the silicon surface. This reaction continuously occurs on the surface of the amorphous silicon film 35 on the circuit substrate 17 shown in FIG. Since the surfaces of the photosensitive resist film 47 and the transparent conductive film 39 are resistant to excited fluorine atoms, the amorphous silicon film 35 in the region not covered with the photosensitive resist film 47 and the transparent conductive film 39 is selected. Removed.

  In a general manufacturing apparatus, etching is performed in plasma containing fluorine generated by high frequency with the circuit board 17 being electrically insulated. At this time, it is known that the circuit board 17 has a negative potential due to the plasma generated by the high frequency. When the substrate potential becomes negative with respect to the plasma potential, ions in the plasma are accelerated and collide with the substrate surface, and the removal of the amorphous silicon film 35 on the substrate surface proceeds. At this time, since ion-like fluorine comes to the negatively charged substrate, the fluorine ions have a direction perpendicular to the substrate. Since the accelerated fluorine ions remove the amorphous silicon film 35 not protected by the resist, the amorphous silicon film 35 below the photosensitive resist film 47 remains without being removed. Since the fluorine ions fly perpendicular to the substrate, the side surface of the remaining amorphous silicon film 35 is nearly vertical, and has almost the same shape as that of the photosensitive resist film 47. By the steps described here, the substrate surface state shown in FIG. 5 changes to the substrate surface state shown in FIG.

  FIG. 6 shows the substrate surface state in the process of separating the amorphous silicon film 35 into pixels. The photosensitive resist film 47 and the transparent conductive film 39 are left because they are difficult to remove with fluorine plasma. On the other hand, the amorphous silicon film 35 is partially removed by fluorine plasma.

  The conventional photodiode element 18 has the shape shown in FIG. 6, and the size of the transparent conductive film 39 is smaller than that of the amorphous silicon film 35. As described above, when the transparent conductive film 39 has a shape smaller than that of the amorphous silicon film 35, the performance of the photodiode element 18 is likely to deteriorate.

  In order to avoid such a problem, even if the amorphous silicon film 35 shown in FIG. 6 is in the state of the substrate surface in the process of pixel separation, the amorphous silicon film 35 is further removed by fluorine plasma, The size of 35 is made smaller than that of the transparent conductive film 39. In the fluorine plasma used in the step of removing the amorphous silicon film 35, electrically neutral fluorine exists. It is known that this excited fluorine atom is not affected by the electric field by the negatively charged circuit board 17 and has an isotropic motion component. The amorphous silicon film 35 can be removed even with excited fluorine atoms, and since the direction of motion is isotropic, the amorphous silicon film 35 easily enters from the side surface of the amorphous silicon film 35 and is located below the photosensitive resist film 47. Remove some of the.

  As a result, as shown in FIG. 7, it is possible to realize a structure in which the area of the amorphous silicon film 35 is smaller than that of the transparent conductive film 39 and the peripheral portion 39a of the transparent conductive film 39 protrudes from the side surface of the amorphous silicon film 35. It becomes.

  Then, the state shown in FIG. 8 is obtained by removing the photosensitive resist film 47 by placing the circuit board 17 in the state shown in FIG. 7 in an organic solvent.

  Thereafter, as shown in FIG. 1, a protective layer 42, which is a liquid transparent resin and is photosensitive, is applied, and the electrical connection portion is exposed by exposure and development with ultraviolet rays. At that time, since the liquid transparent resin is applied onto the circuit board 17, it is easy to fill the transparent resin also in the lower part of the peripheral portion 39a of the transparent conductive film 39 protruding in the eaves-like shape. There are few inconveniences due to the occurrence. Furthermore, the photoelectric conversion substrate 13 is completed by forming the bias electrode 43 using the TFT circuit forming technique and further forming the upper protective layer 44.

  As described above, the area of the transparent conductive film 39 is made larger than the area of the amorphous silicon film 35, and the peripheral portion 39a of the transparent conductive film 39 is projected from the side surface of the amorphous silicon film 35. It is possible to provide a high-performance X-ray detector 18 that prevents deterioration in sensitivity and sensitivity reduction.

  That is, the transparent conductive film 39 formed on the amorphous silicon film 35 supplies a current to the photodiode element 18 composed of the amorphous silicon film 35 and also has a function as an antireflection film. By covering the entire surface of the amorphous silicon film 35 with the transparent conductive film 39 and eliminating the uncovered region, it is possible to supply a current necessary for driving the photodiode element 18, and to improve the responsiveness of the photodiode element 18. Further, the amount of fluorescence incident on the inside of the amorphous silicon film 35 is increased, the sensitivity of the photodiode element 18 is improved, and the performance as the X-ray detector 11 can be improved.

  In order to perform a favorable operation as the photodiode element 18, it is necessary to apply a high electric field of several tens of thousands V / cm to the amorphous silicon film 35. In a state where no light enters from the outside, even if such a high electric field is applied, the leakage current flowing inside the amorphous silicon film 35 is sufficiently small, and no problem occurs in operation as the X-ray detector 11. However, the side surface of the amorphous silicon film 35 is electrically unstable, and the leakage current flowing through the side surface often occupies most of the leakage current flowing through the entire photodiode element 18. The leakage current flowing through the side surface of the amorphous silicon film 35 is strongly influenced by the electric field strength, and the leakage current increases significantly as the electric field strength increases. In the photodiode element 18 according to the prior art, the outer shape of the transparent conductive film 39 is smaller than that of the amorphous silicon film 35. When a high electric field of tens of thousands V / cm necessary for the operation of the photodiode element 18 is applied to the amorphous silicon film 35, The electric field concentrates on the edge of the amorphous silicon film 35, a large electric field strength is generated locally, the leakage current flowing through the side surface of the amorphous silicon film 35 increases, the performance as the photodiode element 18 deteriorates, and the X-ray The performance of the detector 11 is degraded. On the other hand, as in the present embodiment, the area of the transparent conductive film 39 is larger than the area of the amorphous silicon film 35, and the peripheral portion 39a of the transparent conductive film 39 protrudes from the side surface of the amorphous silicon film 35. Even when a high electric field of tens of thousands of V / cm necessary for the operation of the photodiode element 18 is applied to the amorphous silicon film 35, the electric field is concentrated on the end of the amorphous silicon film 35, and a large electric field strength is generated locally. As a result, the leakage current flowing through the side surface of the amorphous silicon film 35 is not increased, and the performance as the photodiode element 18 is improved, whereby the performance of the X-ray detector 11 can be improved.

It is sectional drawing of the radiation detector which shows one embodiment of this invention. It is sectional drawing which shows the manufacturing process of a radiation detector same as the above. It is sectional drawing which shows the manufacturing process following FIG. 2 of a radiation detector same as the above. It is sectional drawing which shows the manufacturing process following FIG. 3 of a radiation detector same as the above. It is sectional drawing which shows the manufacturing process following FIG. 4 of a radiation detector same as the above. It is sectional drawing which shows the manufacturing process following FIG. 5 of a radiation detector same as the above. It is sectional drawing which shows the manufacturing process following FIG. 6 of a radiation detector same as the above. It is sectional drawing which shows the manufacturing process following FIG. 7 of a radiation detector same as the above. It is a perspective view of the decomposition | disassembly state of a radiation detector same as the above. It is a front view which shows a radiation detector same as the above.

Explanation of symbols

11 X-ray detectors as radiation detectors
14 Fluorescence conversion film
17 Circuit board
18 Photodiode elements as photoelectric conversion elements
35 Amorphous silicon film as a semiconductor layer
39 Transparent conductive film

Claims (4)

A radiation detector in which a photoelectric conversion element and a fluorescence conversion film are formed on a circuit board,
The photoelectric conversion element includes a semiconductor layer formed on a circuit board and a transparent conductive film formed on the semiconductor layer, and the entire surface of the semiconductor layer is covered with the transparent conductive film and compared with an area on the semiconductor layer. The radiation detector is characterized in that the transparent conductive film has a large area. A radiation detector in which a photoelectric conversion element and a fluorescence conversion film are formed on a circuit board,
The photoelectric conversion element has a semiconductor layer formed on a circuit board and a transparent conductive film formed on the semiconductor layer, and the transparent conductive film covers the entire surface of the semiconductor layer and is more transparent than the periphery of the semiconductor layer. A radiation detector, wherein a peripheral portion of the conductive film is projected. A method of manufacturing a radiation detector in which a photoelectric conversion element and a fluorescence conversion film are formed on a circuit board,
Laminating a semiconductor layer and a transparent conductive film constituting a photoelectric conversion element on the circuit board;
Removing the transparent conductive film except the formation area of the photoelectric conversion element;
And a step of removing the semiconductor layer so as to have an area smaller than the area of the transparent conductive film, excluding a region where the photoelectric conversion element is formed, and a method for producing a radiation detector. A method of manufacturing a radiation detector in which a photoelectric conversion element and a fluorescence conversion film are formed on a circuit board,
Laminating a semiconductor layer and a transparent conductive film constituting a photoelectric conversion element on the circuit board;
Removing the transparent conductive film except the formation area of the photoelectric conversion element;
And a step of removing the semiconductor layer in a state where a peripheral portion of the transparent conductive film protrudes from a peripheral portion of the semiconductor layer, excluding a formation region of the photoelectric conversion element. Manufacturing method.

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