Patent Publication Number: US-9887224-B2

Title: Detection apparatus having covering layer disposed on interlayer insulating layer in a pixel-array outside region, and detection system including detection apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of co-pending U.S. patent application Ser. No. 14/041,070 filed Sep. 30, 2013, which claims foreign priority benefit of Japanese Patent Application No. 2012-220385 filed Oct. 2, 2012. The disclosures of the above-named applications are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a detection apparatus, a detection system, and a method for producing a detection apparatus that are applied to a medical image diagnostic apparatus, a nondestructive inspection apparatus, an analysis apparatus using radiation, or the like. 
     Description of the Related Art 
     In recent years, thin-film semiconductor production techniques have been applied to the fabrication of radiation detection apparatuses which include an array of pixels (a pixel array). In these apparatuses, each of the pixels is provided by combining a switching element, such as a thin film transistor (TFT), and a conversion element, such as a photodiode, that converts radiation or light into electric charge. A detection apparatus of the related art described in Japanese Patent Laid-Open No. 2007-035773 includes conversion elements provided on electrodes that are disposed on a substrate. The electrodes are composed of a transparent conductive oxide, and are separated from one another on a pixel-by-pixel basis. Furthermore, the detection apparatus of the related art further includes switching elements that are connected to the electrodes via contact holes provided in an interlayer insulating layer. The interlayer insulating layer is disposed between the substrate and the electrodes, and is composed of an organic material. The conversion elements of the detection apparatus of the related art are separated from one another on a pixel-by-pixel basis in such a manner that an impurity semiconductor layer and a semiconductor layer thereof are removed on the interlayer insulating layer. However, in the production of a structure described in Japanese Patent Laid-Open No. 2007-035773, in the case of depositing an impurity semiconductor film, which is to be the impurity semiconductor layer of the conversion elements, and a semiconductor film, which is to be the semiconductor layer of the conversion elements, and in the case of removing the impurity semiconductor film and the semiconductor film on the interlayer insulating layer, a process in which the interlayer insulating layer is exposed is present. More specifically, on the substrate, a region in which no pixel is disposed (a pixel-array outside region) is present outside a region in which multiple pixels are disposed (a pixel-array region). In order to make the thickness of the interlayer insulating layer uniform in the pixel-array region, the interlayer insulating layer is not only disposed within the pixel-array region, but also disposed so as to extend beyond the pixel-array region and reach the pixel-array outside region. Thus, in the case of forming the conversion elements, the exposed area of the interlayer insulating layer in the pixel-array outside region is larger than that of the interlayer insulating layer in the pixel-array region. When the interlayer insulating layer, which is composed of an organic material, is exposed in the case of forming the conversion elements using a chemical vapor deposition (CVD) method, an etching method, or the like, organic contamination in which the organic material is mixed into the conversion elements can occur. A large difference between the exposed areas of the interlayer insulating layer leads to a large difference between the degrees of organic contamination. Thus, there can be a large difference between the degree of organic contamination of the conversion elements located at the edges of the pixel-array region and the degree of organic contamination of the conversion elements located at the center of the pixel-array region. For this reason, the difference between the degrees of organic contamination leads to a large difference between the conversion characteristics of the conversion elements located at the edges of the pixel-array region and the conversion characteristics of the conversion elements located at the center of the pixel-array region. Therefore, the difference in conversion characteristics of the conversion elements located at the edges of the pixel-array region as compared to the conversion characteristics of the conversion elements located at the center of the pixel-array region can cause an image artifact to occur during imaging. 
     SUMMARY OF THE INVENTION 
     The present invention aims to solve such problems, and provides a detection apparatus in which mixing of an organic material from an interlayer insulating layer in an pixel-array outside region into an impurity semiconductor layer and a semiconductor layer of conversion elements is reduced, and in which, consequently, occurrence of an image artifact is reduced. 
     A detection apparatus according to the present invention includes a plurality of conversion elements, an interlayer insulating layer, and a covering layer. Each of the plurality of conversion elements includes an electrode electrically connected to a corresponding one of a plurality of switching elements and a semiconductor layer disposed on the electrode. The interlayer insulating layer is disposed so as to cover the plurality of switching elements and composed of an organic material, and has a surface including a first region and a second region located outside the first region. The electrodes are disposed on the surface of the interlayer insulating layer in the first region. The covering layer is disposed on the surface of the interlayer insulating layer in the second region and composed of an inorganic material. 
     Furthermore, a method for producing a detection apparatus according to the present invention is a method for producing a detection apparatus including a plurality of conversion elements. Each of the plurality of conversion elements includes an electrode electrically connected to a corresponding one of a plurality of switching elements, and a semiconductor layer disposed on the electrode. The method includes the following: a first step of forming an interlayer insulating layer so as to cover the plurality of switching elements, the interlayer insulating layer being composed of an organic material and having a surface including a first region and a second region located outside the first region, and forming the electrodes on the surface of the interlayer insulating layer in the first region and forming a covering layer on the surface of the interlayer insulating layer in the second region, the covering layer being composed of an inorganic material; and a second step of forming the semiconductor layer on the electrodes after the first step. 
     According to the present invention, a detection apparatus can be provided, in which mixing of an organic material from an interlayer insulating layer in an pixel-array outside region into an impurity semiconductor layer and a semiconductor layer of conversion elements is reduced, and in which, consequently, occurrence of an image artifact is reduced. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A, 1B, and 1C  are schematic plan views of a detection apparatus according to a first embodiment. 
         FIGS. 2A, 2B, and 2C  are schematic cross-sectional views of the detection apparatus according to the first embodiment. 
         FIGS. 3A, 3C, 3E, 3G, and 3I  are schematic plan views of mask patterns for explaining a method for producing the detection apparatus according to the first embodiment, and  FIGS. 3B, 3D, 3F, 3H, and 3J  are schematic cross-sectional views of the detection apparatus for explaining the method for producing the detection apparatus according to the first embodiment. 
         FIGS. 4A, 4C, 4E, and 4G  are schematic plan views of mask patterns for explaining the method for producing the detection apparatus according to the first embodiment, and  FIGS. 4B, 4D, 4F, and 4H  are schematic cross-sectional views the detection apparatus for explaining the method for producing the detection apparatus according to the first embodiment. 
         FIG. 5  is a diagram of an equivalent circuit of the detection apparatus according to the first embodiment of the present invention. 
         FIGS. 6A to 6D  are schematic cross-sectional views of a detection apparatus according to a second embodiment. 
         FIGS. 7A to 7C  are schematic cross-sectional views of a detection apparatus according to a third embodiment. 
         FIGS. 8A and 8C  are schematic plan views of mask patterns for explaining a method for producing the detection apparatus according to the third embodiment, and  FIGS. 8B and 8D  are schematic cross-sectional views for explaining the method for producing the detection apparatus according to the third embodiment. 
         FIGS. 9A and 9C  are schematic plan views of mask patterns for explaining an example of another method for producing the detection apparatus according to the third embodiment, and  FIGS. 9B and 9D  are schematic cross-sectional views of a detection apparatus for explaining the example of another method for producing the detection apparatus according to the third embodiment. 
         FIGS. 10A and 10C  are schematic cross-sectional views of a detection apparatus according to a fourth embodiment;  FIG. 10B  is a schematic plan view of a mask pattern. 
         FIGS. 11A, 11C, 11E, and 11G  are schematic plan views of mask patterns for explaining a method for producing the detection apparatus according to the fourth embodiment, and  FIGS. 11B, 11D, 11F, and 11H  are schematic cross-sectional views for explaining the method for producing the detection apparatus according to the fourth embodiment. 
         FIG. 12  is a schematic diagram of a radiation detection system using the detection apparatus according to any one of the embodiments of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be specifically described with reference to the attached drawings. Note that, in the present specification, examples of radiation include not only alpha radiation, beta radiation, and gamma radiation that are beams constituted by particles (including photons) emitted by radioactive decay, but also beams having almost the same or more energy, such as X-rays, a particle beam, and cosmic rays. 
     First Embodiment 
     First, a planar structure of a detection apparatus according to a first embodiment of the present invention will be described using  FIGS. 1A to 1C  and  FIGS. 2A to 2C .  FIG. 1A  is a schematic plan view of a substrate included in the detection apparatus, and  FIG. 1B  is a schematic plan view in which a region IB in  FIG. 1A  is enlarged.  FIG. 1C  is a plan view of each pixel in a region IC illustrated in  FIG. 1B . Note that, in  FIG. 1C , for simplicity, regarding a conversion element, only a first electrode is illustrated. 
     As illustrated in  FIG. 1A , the detection apparatus according to the present invention includes multiple pixels  11  disposed on a substrate  100 . On the substrate  100 , a pixel-array region  20  that is a region in which the multiple pixels  11  are disposed is present. Furthermore, on the substrate  100 , a pixel-array outside region  21  that is a region located outside the pixel-array region  20  is present. In the pixel-array outside region  21 , multiple pixels are not disposed. As illustrated in  FIG. 1C , each of the pixels  11  included in the detection apparatus according to the present invention includes a conversion element  12  that converts radiation or light into electric charge, and a TFT  13  that is a switching element which outputs an electric signal in accordance with the electric charge that the conversion element  12  has. A PIN photodiode is used as the conversion element  12 . The TFTs  13  are provided on the insulating substrate  100  such as a glass substrate. Each of the conversion elements  12  is disposed in such a manner that the conversion element  12  and an interlayer insulating layer  120  composed of an organic material are stacked on a corresponding one of the TFTs  13  and the interlayer insulating layer  120  is sandwiched between the conversion element  12  and the TFT  13 . The interlayer insulating layer  120  is disposed so as to cover the multiple TFTs  13  that are multiple switching elements. Note that, in the present embodiment, the surface of the substrate  100  has regions, and the interlayer insulating layer  120  is disposed so as to cover the surface of the substrate  100  in, among the regions, a region larger than a region in which the multiple TFTs  13  are disposed. Then, as illustrated in  FIG. 1B , the surface of the interlayer insulating layer  120  has regions, and multiple first electrodes  122  are disposed on the surface of the interlayer insulating layer  120  in, among the regions, a first region that is located in the pixel-array region  20 , and, consequently, the multiple pixels  11  including the multiple conversion elements  12  are disposed. In contrast, a covering layer  150  composed of an inorganic material is disposed on the surface of the interlayer insulating layer  120  in, among the regions, a second region that is provided outside the first region and that is located in the pixel-array outside region  21 . Note that, in the present embodiment, the covering layer  150  composed of an inorganic material is disposed so as to cover the second region of the surface of the interlayer insulating layer  120 . Note that the first electrodes  122  correspond to electrodes of conversion elements of the present invention. 
     Next, a cross-sectional structure of the detection apparatus according to the first embodiment of the present invention will be described with reference to  FIG. 1C  and  FIGS. 2A to 2C .  FIG. 2A  is a schematic cross-sectional view taken along the line A-A in  FIG. 1C ,  FIG. 2B  is a schematic cross-sectional view in which a region IIB in  FIG. 2A  is enlarged, and  FIG. 2C  is a schematic cross-sectional view taken along the line B-B in  FIG. 1C . Note that, in  FIGS. 2A  to  2 C, individual insulating layers and individual layers included in the conversion elements  12  that are not illustrated in  FIG. 1C  are also illustrated. 
     Each of the TFTs  13  includes a control electrode  131 , an insulating layer  132 , a semiconductor layer  133 , an impurity semiconductor layer  134  having an impurity concentration higher than that of the semiconductor layer  133 , a first main electrode  135 , and a second main electrode  136  that are provided on the substrate  100  in this order from the substrate side. Certain regions of the impurity semiconductor layer  134  are in contact with the first main electrode  135  and the second main electrode  136 , and a region of the semiconductor layer  133  between regions of the semiconductor layer  133  that are regions in contact with the certain regions is a channel region of the TFT  13 . The control electrode  131  is electrically connected to a corresponding one of control wiring patterns  15 . The first main electrode  135  is electrically connected to a corresponding one of signal wiring patterns  16 . The second main electrode  136  is electrically connected to the first electrode  122  of a corresponding one of the conversion elements  12 . Note that, in the present embodiment, the first main electrodes  135 , the second main electrodes  136 , and the signal wiring patterns  16  are formed together in the same conductive layer, and the first main electrodes  135  are formed as portions of the signal wiring patterns  16 . A protective layer  137  is provided so as to cover the TFTs  13 , the control wiring patterns  15 , and the signal wiring patterns  16 . In the present embodiment, although an inversely-staggered TFT using the semiconductor layer  133  and the impurity semiconductor layer  134  that are composed mainly of amorphous silicon is used as each switching element, the present invention is not limited thereto. For example, a staggered TFT that is composed mainly of polycrystalline silicon can be used, or an organic TFT, an oxide TFT, or the like can be used. 
     The interlayer insulating layer  120  is disposed between the substrate  100  and the multiple first electrodes  122 , which are described below, so as to cover the multiple TFTs  13 , and has contact holes. The first electrode  122  of each of the conversion elements  12  and the second main electrode  136  of a corresponding one of the TFTs  13  are electrically connected to each other in a corresponding one of the contact holes provided in the interlayer insulating layer  120 . 
     Each of the conversion elements  12  includes a corresponding one of the first electrodes  122 , a first-conductivity-type impurity semiconductor layer  123 , a semiconductor layer  124 , a second-conductivity-type impurity semiconductor layer  125 , and a second electrode  126  that are provided on the interlayer insulating layer  120  in this order from the interlayer insulating layer side. Here, the first-conductivity-type impurity semiconductor layer  123  has a first-conductivity-type polarity, and has a first-conductivity-type impurity concentration higher than that of each of the semiconductor layer  124  and the second-conductivity-type impurity semiconductor layer  125 . Furthermore, the second-conductivity-type impurity semiconductor layer  125  has a second-conductivity-type polarity, and has a second-conductivity-type impurity concentration higher than that of each of the first-conductivity-type impurity semiconductor layer  123  and the semiconductor layer  124 . The first conductivity type and the second conductivity type are conductivity types having polarities different from each other. For example, when the first conductivity type is n type, the second conductivity type is p type. A corresponding one of the electrode wiring patterns  14  is electrically connected to the second electrode  126  of the conversion element  12 . The first electrode  122  of the conversion element  12  is electrically connected to the second main electrode  136  of a corresponding one of the TFTs  13  in a corresponding one of the contact holes provided in the interlayer insulating layer  120 . Note that, although a photodiode using the first-conductivity-type impurity semiconductor layer  123 , the semiconductor layer  124 , and the second-conductivity-type impurity semiconductor layer  125  that are composed mainly of amorphous silicon is used in the present embodiment, the present invention is not limited thereto. For example, an element that uses a first-conductivity-type impurity semiconductor layer  123 , a semiconductor layer  124 , and a second-conductivity-type impurity semiconductor layer  125  which are composed mainly of amorphous selenium and that converts radiation directly into electric charge can be used. Note that the second electrodes  126  correspond to other electrodes of the conversion elements of the present invention. 
     As illustrated in  FIGS. 2A to 2C , the multiple first electrodes  122  are disposed on the surface of the interlayer insulating layer  120  in the first region that is located in the pixel-array region  20 , and, consequently, the multiple pixels  11  including the multiple conversion elements  12  are disposed. In contrast, the covering layer  150  composed of an inorganic material is disposed, so as to be in contact with the interlayer insulating layer  120 , on the surface of the interlayer insulating layer  120  in the second region that is provided outside the first region and that is located in the pixel-array outside region  21 . Note that, in the present embodiment, covering members  121  composed of an inorganic material are disposed, so as to be in contact with the interlayer insulating layer  120 , between the multiple first electrodes  122  on the surface of the interlayer insulating layer  120  in the first region that is located in the pixel-array region  20 . The first electrodes  122 , the covering members  121 , and the covering layer  150  are disposed on the interlayer insulating layer  120  so as to cover the surface of the interlayer insulating layer  120 . Thus, in the case of depositing an impurity semiconductor film, which is to be the impurity semiconductor layer  123 , using a CVD method, an evaporation method, a sputtering method, or the like, exposure of the surface of the interlayer insulating layer  120  is reduced. Therefore, mixing of the organic material into the impurity semiconductor layer of the conversion elements  12  included in the pixels  11  located at the edges of the pixel-array region  20  can be reduced. Thus, occurrence of an image artifact due to the differences between the outputs of the pixels  11  that are located at the center of the pixel-array region  20  and the outputs of the pixels  11  that are located at the edges of the pixel-array region  20  can be reduced. Furthermore, in the present embodiment, the impurity semiconductor layer  123 , the semiconductor layer  124 , and the impurity semiconductor layer  125  are separated into pieces on a pixel-by-pixel basis on the covering members  121 . Moreover, in the pixel-array outside region  21 , the impurity semiconductor layer  123 , the semiconductor layer  124 , and the impurity semiconductor layer  125  are removed by dry etching or the like. In the separation and the removal, the covering members  121  and the covering layer  150  serve as an etching stopper layer. Therefore, the interlayer insulating layer  120  is not exposed to etch species used in dry etching, and, consequently, contamination of the individual layers of the conversion elements  12  with the organic material can be reduced. 
     Additionally, an insulating layer  127  and an interlayer insulating layer  128  are disposed so as to cover the conversion elements  12 . The second electrode  126  of each of the conversion elements  12  and a corresponding one of the electrode wiring patterns  14  are electrically connected to each other via a conductive layer  129  in a corresponding one of contact holes provided in the insulating layer  127  and the interlayer insulating layer  128 . In addition, a passivation layer  155  is provided so as to cover the electrode wiring patterns  14 , the conductive layer  129 , and the interlayer insulating layer  128 . 
     Next, a method for producing the detection apparatus according to the first embodiment of the present invention will be described using  FIGS. 3A to 3J  and  FIGS. 4A to 4H . Particularly, a process of forming contact holes in the interlayer insulating layer  120  and processes thereafter will be described in detail using mask patterns and cross-sectional views of the detection apparatus that is being subjected to the processes. Note that each of  FIGS. 3A, 3C, 3E, 3G, 3I, 4A, 4C, 4E, and 4G  is a schematic plan view of a mask pattern of a photomask used in a corresponding one of the processes. Furthermore, each of  FIGS. 3B, 3D, 3F, 3H, 3J, 4B, 4D, 4F, and 4H  is a schematic cross-sectional view taken along the line A-A in  FIG. 1C  in a corresponding one of the processes. 
     First, the multiple TFTs  13  are provided on the insulating substrate  100 , and the protective film  137  is provided so as to cover the multiple TFTs  13 . Portions of the protective film  137  that are portions located on the second main electrodes  136  and that are to be electrically connected to the photodiodes are subjected to etching, thereby providing contact holes in the protective film  137 . Then, in the process illustrated in  FIG. 3B , using a coating apparatus such as a spinner, a film composed of an acrylic resin that is an organic material having a photosensitivity is deposited as an interlayer insulating film so as to cover the TFTs  13  and the protective film  137 . Alternatively, a polyimide resin or the like can be used as the organic material having a photosensitivity. Then, a light exposure process and a development process are performed using the mask illustrated in  FIG. 3A , thereby forming the interlayer insulating layer  120  having contact holes. 
     Next, in the process illustrated in  FIG. 3D , a conductive film is deposited so as to cover the interlayer insulating layer  120 . Then, the conductive film is subjected to etching using the mask illustrated in  FIG. 3C , thereby forming the first electrodes  122  of the conversion elements  12 . Note that, in the present embodiment, a transparent conductive oxide film that is composed of ITO and that is an amorphous film is used as the conductive film. The transparent conductive oxide film is subjected to wet etching using the mask illustrated in  FIG. 3E , and subjected to an annealing process so as to be changed to a polycrystalline film, thereby forming the first electrodes  122  of the conversion elements  12 . However, a film composed of a metallic material may be used as the conductive film. 
     Next, in the process illustrated in  FIG. 3F , an insulating film that is composed of a typical inorganic material, such as a silicon nitride film or a silicon oxide film, is deposited using a plasma CVD method so as to cover the interlayer insulating layer  120 . Then, the insulating film is subjected to etching using the mask illustrated in  FIG. 3E , whereby the covering members  121  and the covering layer  150  are formed between the multiple first electrodes  122  on the surface of the interlayer insulating layer  120  in the first region and on the surface of the interlayer insulating layer  120  in the second region, respectively. Accordingly, the surface of the interlayer insulating layer  120  is covered with the multiple covering members  121 , the multiple first electrodes  122 , and the covering layer  150 . In the present embodiment, the process illustrated in  FIG. 3D  and the process illustrated in  FIG. 3F  correspond to a first step of the present invention. Note that, in the present embodiment, an example is described, in which an inorganic insulating material that is the same as the material that the covering members  121  are composed of is used as the material that the covering layer  150  is composed of, and in which the covering layer  150  and the covering members  121  are formed together. However, the present invention is not limited thereto. For example, the covering members  121  and the covering layer  150  may be formed in different processes. Furthermore, the material that the covering layer  150  is composed of is not limited to an inorganic insulating material, and any inorganic film that can cover the surface of the interlayer insulating layer  120  may be used. For example, among regions of the covering layer  150 , regions that are in contact with the first electrodes  122  and the impurity semiconductor layer  123  may be formed of an inorganic insulating material, and the other regions may be formed of an inorganic conductive material, such as ITO, Al, or Cu. 
     Next, in the process illustrated in  FIG. 3H , an amorphous silicon film in which a pentavalent element, such as phosphorus, is implanted as an impurity is deposited as a first-conductivity-type impurity semiconductor film  123 ′ using a plasma CVD method so as to cover the covering members  121  and the first electrodes  122 . Next, a semiconductor film  124 ′ that is an amorphous silicon film and an amorphous silicon film, as a second-conductivity-type impurity semiconductor film  125 ′, in which a trivalent element, such as boron, is implanted as an impurity are deposited in this order using a plasma CVD method or the like. In the case of depositing the impurity semiconductor film  123 ′, when the interlayer insulating layer  120  is not covered with the covering members  121 , the covering layer  150 , and the first electrodes  122 , the interlayer insulating layer  120  is exposed to plasma. When the interlayer insulating layer  120  composed of an organic material is exposed to plasma, the organic material spatters, and mixes into the impurity semiconductor film  123 ′. Thus, junctions between the first electrodes  122  and the impurity semiconductor layer  123  are contaminated in some cases. Particularly, the exposed area of the interlayer insulating layer  120  in the pixel-array outside region  21  is larger than the exposed area of the interlayer insulating layer  120  in the pixel-array region  20 . Thus, the degree of organic contamination of the conversion elements  12  included in the pixels  11  located at the edges of the pixel-array region  20  is higher than that of organic contamination of the conversion elements  12  included in the pixels  11  located at the center of the pixel-array region  20 . For this reason, in the present embodiment, a structure is used, in which the surface of the interlayer insulating layer  120  in the pixel-array region  20  is covered with the covering members  121 , the first electrodes  122 , and the covering layer  150 , and, in which, consequently, the surface of the interlayer insulating layer  120  is not exposed in the case of depositing the impurity semiconductor film  123 ′ that is to be the first-conductivity-type impurity semiconductor layer  123 . Accordingly, in the case of depositing the impurity semiconductor film  123 ′ that is to be the impurity semiconductor layer  123 , mixing of the organic material into the impurity semiconductor film  123 ′ due to scattering of the organic material can be reduced. Thus, occurrence of an image artifact can be reduced. Next, a transparent conductive oxide film is deposited using a sputtering method so as to cover an impurity semiconductor film  125 ′. Next, the transparent conductive oxide film is subjected to wet etching using the mask illustrated in  FIG. 3G , thereby forming the second electrodes  126  of the conversion elements  12 . Note that, in the present embodiment, a transparent conductive oxide is used as the material that the second electrodes  126  are composed of. However, the present invention is not limited thereto. Any conductive film may be used. For example, in the case where an element that converts radiation directly into electric charge is used as each of the conversion elements  12 , a conductive film that radiation easily passes through, such as an Al film, can be used. 
     Next, in the process illustrated in  FIG. 3J , the impurity semiconductor film  125 ′, the semiconductor film  124 ′, and the impurity semiconductor film  123 ′ are removed by dry etching using the mask illustrated in  FIG. 3I . Accordingly, the conversion elements  12  are separated from one another on a pixel-by-pixel basis, and the impurity semiconductor film  125 ′, the semiconductor film  124 ′, and the impurity semiconductor film  123 ′ in the pixel-array outside region  21  are removed. In the conversion elements  12  that have been separated from one another, the impurity semiconductor layer  125 , the semiconductor layer  124 , and the impurity semiconductor layer  123  are formed. 
     Next, in the process illustrated in  FIG. 4B , an insulating film composed of an inorganic material, such as a silicon nitride film, is deposited using a plasma CVD method so as to cover the conversion elements  12  and the covering members  121 . Also in the case of depositing this insulating film, a structure in which exposure of the interlayer insulating layer  120  is reduced by the covering layer  150  is used. Thus, contamination of the individual layers with the organic material can be reduced. Then, the insulating film is subjected to dry etching using the mask illustrated in  FIG. 4A , thereby forming the insulating layer  127  having contact holes. 
     Next, in the process illustrated in  FIG. 4D , a layer composed of an acrylic resin that is an organic material having a photosensitivity is deposited as an interlayer insulating layer so as to cover the second electrodes  126  and the insulating layer  127 . Then, the interlayer insulating layer  128  having contact holes is formed using the mask illustrated in  FIG. 4C . 
     Next, in the process illustrated in  FIG. 4F , a transparent conductive oxide film is deposited using a sputtering method. Next, the transparent conductive oxide film is subjected to wet etching using the mask illustrated in  FIG. 4E , thereby forming the conductive layer  129 . 
     Next, in the process illustrated in  FIG. 4H , a conductive film, such as an Al film, that is to be the electrode wiring patterns  14  is deposited using a sputtering method. Then, the conductive film is subjected to wet etching using the mask illustrated in  FIG. 4G , thereby forming the electrode wiring patterns  14 . By performing this process, the electrode wiring patterns  14  and the second electrodes  126  of the conversion elements  12  are electrically connected to each other with the conductive layer  129 . In this case, because the conductive layer  129  is formed of a transparent conductive oxide, a reduction in the aperture ratio can be prevented. 
     Then, the passivation layer  155  is formed so as to cover the electrode wiring patterns  14 , the conductive layer  129 , and the interlayer insulating layer  128 , thereby obtaining the structure illustrated in  FIG. 2A . Also in the case of forming the passivation layer  155 , a structure is used, in which the interlayer insulating layer  120  is not exposed in the outside of the area in which the pixels are disposed. Thus, contamination of the individual layers with the organic material can be reduced. In the present embodiment, the process illustrated in  FIG. 3H  and the processes thereafter correspond to a second step of the present invention. 
     Next, a schematic equivalent circuit of the detection apparatus according to the first embodiment of the present invention will be described using  FIG. 5 . Note that, in  FIG. 5 , for simplicity of description, a diagram of an equivalent circuit in three rows and three columns is used. However, the present invention is not limited thereto. The detection apparatus has a pixel array in n rows and m columns (where each of n and m is a natural number equal to or larger than two). Regarding the detection apparatus according to the present embodiment, a conversion unit  3  including multiple pixels  1  that are arranged along the row direction and the column direction is provided on the surface of the substrate  100 . Each of the pixels  1  includes a corresponding one of the conversion elements  12 , which convert radiation or light into electric charge, and a corresponding one of the TFTs  13 , which output electric signals in accordance with the electric charge that the conversion elements  12  have. A scintillator (not illustrated) that performs wavelength conversion so that radiation will be converted into visible light may be disposed on the surface of the conversion elements  12  on the second electrode  126  side. The electrode wiring patterns  14  are connected to the second electrodes  126  of the conversion elements  12  as a wiring pattern common to the conversion elements  12 . The control wiring patterns  15  are connected to the control electrodes  131  of the multiple TFTs  13 , as wiring patterns common to the TFTs  13  arranged along the row direction, and are electrically connected to a driving circuit  2 . The driving circuit  2  sequentially or simultaneously supplies driving pulses to the multiple control wiring patterns  15 , which are arranged along the column direction, whereby electric signals are output, in parallel, from the pixels  1  on a row-by-row basis to the multiple signal wiring patterns  16 , which are arranged along the row direction. The signal wiring patterns  16  are connected to the first main electrodes  135  of the multiple TFTs  13 , as wiring patterns common to the TFTs  13  arranged along the column direction, and are electrically connected to a reading circuit  4 . The reading circuit  4  includes, for each of the signal wiring patterns  16 , an integrating amplifier  5  that integrates and amplifies the electric signal output from the signal wiring pattern  16 , and a sample and hold circuit  6  that samples and holds the electric signal which has been amplified and output by the integrating amplifier  5 . The reading circuit  4  further includes a multiplexer  7  that converts the electric signals output in parallel from the multiple sample and hold circuits  6  into an electric signal in series, and an A/D converter  8  that converts the output electric signal into digital data. A reference potential Vref is supplied from a power supply circuit  9  to the non-inverting input terminals of the integrating amplifiers  5 . Furthermore, the power supply circuit  9  is electrically connected to the multiple electrode wiring patterns  14  that are arranged along the row direction, and supplies a bias potential Vs to the second electrodes  126  of the conversion elements  12 . 
     Hereinafter, an operation of the detection apparatus according to the present embodiment will be described. The reference potential Vref is supplied via the TFTs  13  to the first electrodes  122  of the conversion elements  12 . The bias potential Vs that is necessary to perform electron-hole pair separation for electric charge generated from radiation or visible light is supplied to the second electrodes  126 . In this state, radiation that passes through a subject or visible light based on the radiation enters the conversion elements  12 , and is converted into electric charge. The electric charge is accumulated in the conversion elements  12 . The driving pulses applied to the control wiring patterns  15  from the driving circuit  2  cause the TFTs  13  to enter a conduction state, whereby electric signals based on the electric charge are output to the signal wiring patterns  16 . The electric signals are read to the outside as digital data by the reading circuit  4 . 
     Second Embodiment 
     Next, a structure of each pixel included in a detection apparatus according to a second embodiment of the present invention will be described using  FIGS. 6A to 6D . Each of  FIGS. 6A to 6D  is a schematic cross-sectional view taken along the line A-A in  FIG. 1C . 
     The difference of the present embodiment from the first embodiment is the following. In other words, in each of the contact holes in which the conversion elements  12  and the TFTs  13  are connected to each other, a protective member  160  for protecting the second main electrode  136  and the protective film  137  is disposed in accordance with the stepped portion of the protective film  137  and the stepped portion of the interlayer insulating layer  120 . 
     In the process illustrated in  FIG. 3F , in the case of etching performed in order to form the covering members  121  and the covering layer  150 , the second main electrodes  136  and the protective film  137  need to be protected by the first electrodes  122 . However, protection of the second main electrodes  136  and the protective film  137  is impossible in some cases because of the crystallizability or thickness of the first electrodes  122 . More specifically, in each of the contact holes of the interlayer insulating layer  120 , when a conductive film that is to be the first electrode  122  is deposited on the stepped portion of the protective film  137  or the stepped portion of the interlayer insulating layer  120 , the crystallizability of the first electrode  122  on the stepped portion decreases. The first electrode  122  on the stepped portion is easily subjected to etching. Thus, in the case of forming the covering members  121  and the covering layer  150 , protection of the second main electrodes  136  and the protective film  137  with the first electrodes  122  is impossible, and, consequently, the second main electrode  136  and the insulating layer  127  are undesirably subjected to etching. 
     Thus, in the structure in the present embodiment, in each of the contact holes of the interlayer insulating layer  120 , the protective member  160  for protecting the second main electrode  136  and the protective film  137  is disposed in accordance with the stepped portion of the protective film  137  and the stepped portion of the interlayer insulating layer  120 . Therefore, in the process illustrated in  FIG. 3F , the second main electrodes  136  and the protective film  137  are prevented from being undesirably subjected to etching, and, consequently, the second main electrodes  136  and the protective film  137  can be protected. 
     In a structure illustrated in  FIG. 6A , in each of the contact holes of the interlayer insulating layer  120 , the protective member  160  is disposed so as to cover the stepped portion of the protective film  137  and the stepped portion of the interlayer insulating layer  120 . A method for producing the structure illustrated in  FIG. 6A  will be described below. In the present embodiment, in the process illustrated in  FIG. 3F  in the first embodiment, the covering members  121  and the covering layer  150  are formed, and, simultaneously, the protective members  160  are formed from the same material, thereby obtaining the structure illustrated in  FIG. 6A . Note that, in  FIG. 6A , a structure is illustrated, in which each of the protective members  160  covers only the stepped portion of the protective film  137  and the stepped portion of the interlayer insulating layer  120 . However, the present invention is not limited thereto. 
     For example, as illustrated in  FIG. 6B , a structure may be used, in which each of the protective members  160  is disposed so as to also cover the surface of the protective film  137  located in the bottom surface of a corresponding one of the contact holes, in addition to the stepped portion of the protective film  137  and the stepped portion of the interlayer insulating layer  120 . With this structure, the protective film  137  can be more assuredly protected, compared with that with the structure illustrated in  FIG. 6A . 
     Furthermore, as illustrated in  FIG. 6C , a structure may be used, in which each of the protective members  160  is disposed so as to cover the entire bottom surface of a corresponding one of the contact holes of the interlayer insulating layer  120 . With this structure, the second main electrodes  136  can be more assuredly protected, compared with that with the structure illustrated in  FIG. 6B . 
     Note that, regarding the protective members  160  illustrated in  FIGS. 6A to 6C , when each of the protective members  160  is formed so as to also cover the surface of the first electrode  122  located outside a corresponding one of the contact holes of the interlayer insulating layer  120 , the protective member  160  can cover the entire stepped portion of the first electrode  122  that is stepped because of the contact hole. Even when the protective members  160  are formed from an inorganic insulating layer and, consequently, the area of each of the protective members  160  increases, the impurity semiconductor layer  123  is disposed on the entire surface of the protective member  160 . Thus, electric charge can be collected without any problem. 
     Note that, with reference to  FIGS. 6A to 6C , a method is described, in which the protective members  160  are formed simultaneously with formation of the covering members  121  and the covering layer  150 . However, the present invention is not limited thereto. Before the process illustrated in  FIG. 3F  is performed, the protective members  160  may be formed in advance. In this case, a material that has a conductivity and that has a resistance to etching which is to be performed for the covering members  121  and the covering layer  150  needs to be used as the material that the protective members  160  are composed of. For example, in the case where the covering members  121  and the covering layer  150  are to be composed of silicon nitride and where the covering members  121  and the covering layer  150  are to be formed by wet etching using hydrofluoric acid or the like, the material that the protective members  160  are composed of may be any one of the following materials. Examples of the material that the protective members  160  are composed of include metallic materials such as Mo, Cr, Pt, and Au, an alloy material such as MoCr, and semiconductor materials such as titanium oxide and titanium nitride that have resistance to hydrofluoric acid. Alternatively, in the case where the covering members  121  and the covering layer  150  are to be composed of silicon nitride and where the covering members  121  and the covering layer  150  are to be formed by dry etching, any one of alloy materials such as MoCr and MoW, and a conductive material such as WN that have resistance to dry etching needs to be used. In the case of forming the protective members  160  in advance, as illustrated in  FIG. 6D , a structure is used, in which, each of the protective members  160  is disposed between the second main electrode  136  and the first electrode  122  under a corresponding one of the contact holes of the interlayer insulating layer  120 . 
     Third Embodiment 
     Next, a structure of each pixel included in a detection apparatus according to a third embodiment of the present invention will be described using  FIGS. 7A to 7C .  FIG. 7A  is a schematic cross-sectional view taken along the line A-A in  FIG. 1C .  FIG. 7B  is a schematic cross-sectional view in which a region VIIB in  FIG. 7A  is enlarged.  FIG. 7C  is a schematic cross-sectional view taken along the line B-B in  FIG. 1C . Furthermore, elements the same as the elements described in the foregoing embodiments are denoted by the same reference numerals, and a detailed description thereof is omitted. 
     In the first embodiment, ends of the first electrodes  122  are disposed under the covering layer  150 . In contrast, in the present embodiment, ends of the first electrodes  122  are disposed between the covering layer  150  and the impurity semiconductor layer  123 . 
     Next, a method for producing the detection device according to the third embodiment of the present invention will be described using  FIGS. 8A to 8D . Note that, regarding processes the same as the processes described in the first embodiment, a detailed description thereof is omitted. Note that each of  FIGS. 8A and 8C  is a schematic plan view of a mask pattern of a photomask used in a corresponding one of the processes for the pixel illustrated in  FIG. 1C . Furthermore, each of  FIGS. 8B and 8D  is a schematic cross-sectional view taken along the line A-A in  FIG. 1C  in a corresponding one of the processes. Note that, because a process of forming contact holes in the interlayer insulating layer  120  and processes that have been performed before the process is performed are the same as the processes described in the first embodiment, a detailed description thereof is omitted. 
     First, in the process illustrated in  FIG. 8B , an insulating film composed of a typical inorganic material, such as a silicon nitride film or a silicon oxide film, is deposited using a CVD method so as to cover the interlayer insulating layer  120 . Then, the covering members  121  and the covering layer  150  are formed using the mask illustrated in  FIG. 8A . 
     Next, in the process illustrated in  FIG. 8D , a conductive film composed of Al, ITO, or the like is deposited so as to cover the interlayer insulating layer  120 , the covering members  121 , and the covering layer  150 . Then, the conductive film is subjected to etching using the mask illustrated in  FIG. 8C , thereby forming the first electrodes  122  of the conversion elements  12 . In this case, the surface of the interlayer insulating layer  120  is covered with the covering members  121 , the first electrodes  122 , and the covering layer  150 . Thus, in the process following the process illustrated in  FIG. 8D , in the case of depositing an impurity semiconductor layer, which is to be the impurity semiconductor layer  123 , using a CVD method, mixing of the organic material into the first-conductivity-type impurity semiconductor layer due to scattering of the organic material can be reduced. Therefore, occurrence of an image artifact can be reduced. In the present embodiment, the process illustrated in  FIG. 8B  and the process illustrated in  FIG. 8D  correspond to the first step of the present invention. 
     Because the process of depositing the impurity semiconductor layer and processes thereafter, which correspond to the second step, are the same as the processes described as examples in the first embodiment, a description thereof is omitted. Note that, in the present embodiment, an example is described, in which an inorganic insulating film the same as the material that the covering members  121  are formed from is used as the material that covering layer  150  is formed from, and in which the covering members  121  and the covering layer  150  are formed together. However, the present invention is not limited thereto. As described in the first embodiment, even in the present embodiment, another structure and method can be applied. 
     Furthermore, in the present embodiment, a structure may be used, in which only the inner sides of portions that are portions of the protective film  137  and that are to be contact holes are subjected to etching using a mask illustrated in  FIG. 9A  instead of the mask illustrated in  FIG. 8A . In this case, a structure illustrated in  FIG. 9B  is obtained. 
     Furthermore, in the present embodiment, without providing contact holes in the protective film  137  in advance, portions of a protective film  137 ′ that are portions to be contact holes and an inorganic insulating film  121 ′ may be subjected to, together, etching using a mask illustrated in  FIG. 9C  instead of the mask illustrated in  FIG. 8A , whereby the contact holes of the protective film  137 , the covering members  121 , and the covering layer  150  may be formed together. In this case, a structure illustrated in  FIG. 9D  is obtained. 
     Even with any one of the structures illustrated in  FIGS. 9B and 9D , as with the structure illustrated in  FIG. 8B , mixing of the organic material into the first-conductivity-type impurity semiconductor layer due to scattering of the organic material can be reduced. Thus, occurrence of an image artifact can be reduced. 
     Fourth Embodiment 
     Next, a structure of each pixel included in a detection apparatus according to a fourth embodiment of the present invention will be described using  FIGS. 10A to 10C .  FIGS. 10A and 10C  are cross-sectional views taken along the line A-A in  FIG. 1C . Note that  FIG. 10B  is a schematic plan view of a mask pattern of a photomask used in a process. Note that elements the same as the elements described in the foregoing embodiments are denoted by the same reference numerals, and a detailed description thereof is omitted. 
     In the first embodiment, the semiconductor layer  124  and the impurity semiconductor layer  125  are separated into pieces on a pixel-by-pixel basis, and the second electrodes  126  are separated from one another on a pixel-by-pixel basis. In contrast, in the present embodiment, as illustrated in  FIG. 10A , a semiconductor layer  124   a  and an impurity semiconductor layer  125   a  are not separated into pieces on a pixel-by-pixel basis, and second electrodes  126   a  are not separated from one another on a pixel-by-pixel basis. However, the first electrodes  122  are separated from one another on a pixel-by-pixel basis, and the impurity semiconductor layer  123  are separated into pieces on a pixel-by-pixel basis. Thus, the conversion elements  12  are individualized on a first-electrode- 122 -by-first-electrode- 122  basis. Therefore, in the structure in the present embodiment, the aperture ratio can be increased, compared with that in the structure in the first embodiment. Furthermore, because the second electrodes  126   a  are not separated from one another on a pixel-by-pixel basis, it is not necessary to provide the electrode wiring patterns  14  that cause the aperture ratio to be reduced. However, in the case where the resistance based on only the resistance of the second electrodes  126   a  is high, the electrode wiring patterns  14  may be provided. In this case, the semiconductor layer  124   a  is not separated into pieces on a pixel-by-pixel basis, and the second electrodes  126   a  are not separated from one another on a pixel-by-pixel basis. Thus, the electrode wiring patterns  14  can be disposed so that the positions of the electrode wiring patterns  14  include positions at which the orthogonal projections of the electrode wiring patterns  14  do not overlap with the impurity semiconductor layer  123 . Thus, the electrode wiring patterns  14  can be provided without reducing the aperture ratio. Furthermore, in the present embodiment, the covering members  121  are not provided. Even without the covering members  121 , there is no large difference between the degrees of organic contamination of the individual conversion elements  12 . Thus, an image artifact does not become a problem. The same is also true in the other embodiments of the present invention. 
     Next, a method for producing the detection apparatus according to the fourth embodiment of the present invention will be described using  FIGS. 11A to 11H . Note that each of  FIGS. 11A, 11C, 11E, and 11G  is a schematic plan view of a mask pattern of a photomask used in a corresponding one of processes. Furthermore, each of  FIGS. 11B, 11D, 11F, and 11H  is a schematic cross-sectional view taken along the line A-A in  FIG. 1C  in a corresponding one of the processes. Note that, regarding processes the same as the processes described in the first embodiment, a detailed description thereof is omitted. More specifically, a process of forming the first electrodes  122  and processes that have been performed before the process is performed are the same as the processes described using  FIGS. 3A to 3D . Thus, processes thereafter will be described. 
     First, in the process illustrated in  FIG. 11B , a film composed of a typical inorganic material, such as a silicon nitride film or a silicon oxide film, is deposited so as to cover the interlayer insulating layer  120  and the first electrodes  122 . Then, in the pixel-array outside region  21 , the covering layer  150  is formed using the mask illustrated in  FIG. 9A . In this case, the interlayer insulating layer  120  is exposed at most only between the multiple first electrodes  122 . The exposed area of the interlayer insulating layer  120  between the first electrodes  122  is at most within 20% of the total area of the interlayer insulating layer  120  per pixel, and is much smaller than the area of the interlayer insulating layer  120  in the pixel-array outside region  21 . Thus, the exposure of the interlayer insulating layer  120  is not a factor causing organic contamination, for example, that results in occurrence of an image artifact. Note that the covering layer  150  may completely cover the surface of the interlayer insulating layer  120  in the pixel-array outside region  21 . Alternatively, the covering layer  150  may not completely cover the surface of the interlayer insulating layer  120  if the exposed area of the surface of the interlayer insulating layer  120  in the pixel-array outside region  21  is almost equal to that of the surface of the interlayer insulating layer  120  in the pixel-array region  20 . The same is also true in the other embodiments of the present invention. In the present embodiment, the process illustrated in  FIG. 11B  corresponds to the first step of the present invention. 
     Next, in the process illustrated in  FIG. 11D , an amorphous silicon film in which a pentavalent element, such as phosphorus, is implanted as an impurity is deposited as the first-conductivity-type impurity semiconductor film  123 ′ using a plasma CVD method or the like so as to cover the covering layer  150  and the first electrodes  122 . Then, one portion of the impurity semiconductor film  123 ′ is removed by dry etching using the mask illustrated in  FIG. 11C , thereby forming the impurity semiconductor layer  123 . 
     Next, in the process illustrated in  FIG. 11F , an amorphous silicon film is deposited as the semiconductor film  124 ′ using a plasma CVD method or the like so as to cover the covering layer  150  and the impurity semiconductor layer  123 . Next, an amorphous silicon film in which a trivalent element, such as boron, is implanted as an impurity is deposited as the second-conductivity-type impurity semiconductor film  125 ′ using a plasma CVD method or the like. 
     Next, a transparent conductive oxide film  126 ′ is deposited using a sputtering method so as to cover the impurity semiconductor film  125 ′. Then, the transparent conductive oxide film  126 ′ is subjected to wet etching using the mask illustrated in  FIG. 11E , thereby forming the second electrodes  126   a.    
     Next, in the process illustrated in  FIG. 11H , the impurity semiconductor film  125 ′ and the semiconductor film  124 ′ in the pixel-array outside region  21  are subjected to dry etching using the mask illustrated in  FIG. 11G , thereby forming an impurity semiconductor layer  125   a  and a semiconductor layer  124   a.    
     Next, the passivation layer  155  is formed so as to cover the second electrodes  126   a  and the covering layer  150 , thereby obtaining the structure illustrated in  FIG. 10A . In the present embodiment, the process illustrated in  FIG. 11D , the process illustrated in  FIG. 11F , and the process illustrated in  FIG. 11H  correspond to the second step of the present invention. 
     Note that, also in the present embodiment, the covering members  121  may be disposed between the first electrodes  122 . 
     Furthermore, also in the present embodiment, as described in the second embodiment, the protective members  160  may be disposed in the contact holes of the interlayer insulating layer  120 . Furthermore, also in the present embodiment, as in the third embodiment, a structure in which ends of the first electrodes  122  are disposed between the covering layer  150  and the impurity semiconductor layer  123  may be used. 
     Application Embodiment 
     Next, a radiation detection system using the detection apparatus according to any one of the embodiments of the present invention will be described using  FIG. 12 . 
     As illustrated in  FIG. 12 , X-rays  6060  generated by an X-ray tube  6050  that is a radiation source pass through a body part  6062  of a patient or subject  6061 , and enter individual conversion elements included in a radiation detection apparatus  6040 . Information concerning the inside of the body of the patient  6061  is included in the X-rays that have entered the conversion elements. Radiation is converted into electric charges by a conversion unit  3  ( FIG. 5 ) on the basis of the X-rays that have entered the conversion elements, thereby obtaining electric information. This information is converted into digital data, subjected to image processing by an image processor  6070  that is a signal processing unit, and can be monitored on a display screen  6080  that is a display unit of a control room. 
     Furthermore, this information can be transferred to a remote location by a transmission processing unit such as a wired or wireless network  6090 , and can be displayed on a display screen  6081  that is a display unit or stored in a recording unit such as an optical disk, for example, at another place such as a doctor&#39;s room. A doctor in the remote location can make a diagnosis. Furthermore, the information can be recorded, by a film processor  6100  that is a recording unit, in a film  6110  that is a recording medium. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2012-220385 filed Oct. 2, 2012, which is hereby incorporated by reference herein in its entirety.