Patent Publication Number: US-2015084149-A1

Title: Radiation detector and radiation detection apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2013-195677 filed on Sep. 20, 2013 in Japan, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to radiation detectors and radiation detection apparatuses. 
     BACKGROUND 
     In a radiation imaging system such as a radiography apparatus or a computerized tomography (CT) system, X-ray beams from an X-ray source are emitted to a test subject or an object such as a patient or baggage. An X-ray beam attenuates as passing through a test subject, and then enters a radiation detector. As detecting pixels are arranged in an array in a radiation detector, an X-ray that has entered the radiation detector enters the detecting pixels arranged in an array. The intensity of radiation to be detected by each detecting pixel normally depends on X-ray attenuance. The respective detecting elements of the detecting pixels arranged in an array generate electrical signals corresponding to attenuated X-ray beams sensed by the respective detecting elements independently of one another. These signals are transmitted to a data processing system for analysis, and an image is eventually formed by the data processing system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view showing a radiation detector according to a first embodiment; 
         FIG. 2  is a plan view showing one pixel of the radiation detector of the first embodiment; 
         FIG. 3  is a plan view showing the pixel array of the radiation detector of the first embodiment; 
         FIG. 4  is a cross-sectional view showing a radiation detector according to a first modification of the first embodiment; 
         FIG. 5  is a cross-sectional view showing a radiation detector according to a second modification of the first embodiment; 
         FIGS. 6(   a ) through  6 ( c ) are cross-sectional views showing the process of manufacturing the radiation detector of the first embodiment; 
         FIGS. 7(   a ) through  7 ( c ) are cross-sectional views showing the process of manufacturing the radiation detector of the first embodiment; 
         FIGS. 8(   a ) through  8 ( c ) are cross-sectional views showing the process of manufacturing the radiation detector of the first embodiment; 
         FIG. 9  is a cross-sectional view showing a radiation detector according to a second embodiment; 
         FIG. 10  is a cross-sectional view showing a radiation detector according to a third embodiment; 
         FIGS. 11(   a ) and  11 ( b ) are cross-sectional views showing the process of manufacturing the radiation detector of the third embodiment; and 
         FIGS. 12(   a ) through  12 ( c ) are diagrams for explaining a radiation detection apparatus according to a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A radiation detector according to an embodiment includes: a semiconductor substrate having a first surface and a second surface located on the opposite side from the first surface; a light detecting unit provided on a side of the first surface of the semiconductor substrate; a first insulating film provided on the first surface to cover the light detecting unit; a second insulating film covering the first insulating film; a scintillator provided on the second insulating film, and converting radiation into visible light; a first opening penetrating through the semiconductor substrate and the first insulating film; an interconnection provided between the first insulating film and the second insulating film, and connected to the light detecting unit; a first electrode connected to the interconnection through a bottom portion of the first opening, the first electrode being provided on a bottom surface and a side surface of the first opening and on part of the second surface; a second electrode provided on a region in the second surface of the semiconductor substrate, the region opposing at least a part of the light detecting unit; a second opening provided in the semiconductor substrate, the second opening being located in a region, the region surrounding the first electrode and not surrounding the second electrode; and an insulating resin layer covering the first electrode, the second electrode, the first opening, and the second opening, the insulating resin layer having a third opening and a fourth opening provided therein, the third opening leading to the first electrode, the fourth opening leading to the second electrode. 
     Before embodiments of the present invention are described, how the embodiments have been developed is explained. 
     In a radiation detector of indirect conversion type, visible light that is generated from radiation entering a scintillator is detected by light detecting units such as photodiodes or photomultipliers. 
     Regarding a radiation detector that includes such a scintillator and pixels with light detecting units arranged in an array, there is a demand for formation of a large number of pixels at a high density so as to obtain high-quality CT images with arrayed pixels. However, it is difficult to extract electrical signals from pixels formed at a high density with interconnections connected by wire bonding. In view of this, through electrodes that are called TSV (Through Silicon Via) electrodes are normally required. 
     In a case where TSV electrodes are formed on light detecting units, the TSV electrodes are normally formed after the light detecting units are formed in a semiconductor substrate (“via-last”). In a case where the light detecting units are formed in a semiconductor substrate after the TSV electrodes are formed (“via-first”), the material of the TSV electrodes needs to be capable of tolerating various kinds of load (such as heat history) during the light detecting unit manufacturing process, and therefore, the material of the TSV electrodes is limited. 
     By a general method of manufacturing the TSV electrodes, through holes for forming the TSV electrodes are formed in the semiconductor substrate having the light detecting units formed therein, and insulating layers for insulating and isolating the TSV electrodes from the semiconductor substrate are formed. After that, the TSV electrodes are completed by using a plating technique or the like. At this point, the breakdown voltage of the insulating films (hereinafter also referred to as TSV insulating films) formed on the side walls of the through holes is important. Particularly, in the case of an avalanche photodiode (hereinafter also referred to as an APD) that operates in Geiger mode, a relatively high voltage of approximately 20 V to 80 V is applied between the cathode electrode and the anode electrode of the APD for driving. Therefore, the TSV insulating film for the APD needs to have a sufficiently high breakdown voltage. That is, in a case where TSV electrodes are formed on APDs, it is necessary to pay enough attention to the breakdown voltage of the TSV insulating films. 
     So as to improve the breakdown voltage of TSV insulating films, the inventors have considered the following aspects. 
     In a case where TSV electrodes are formed, it is difficult to form the openings for through holes if the semiconductor substrate is thick. Therefore, a supporting member is bonded to the substrate with an adhesive agent, and the substrate is thinned by polishing. After that, the openings for through holes are formed. Therefore, in a case where TSV insulating films are formed, it is necessary to pay attention to the heat resistance of the adhesive agent. For example, in a case where TSV insulating films are formed by plasma CVD (Chemical Vapor Deposition), by which insulating films can be formed at relatively low temperatures, film quality and breakdown voltage become lower than those of thermally-oxidized films or CVD films formed by high-temperature plasma, if SiO 2  films are formed at a low temperature such as 200° C., for example, by taking into account the heat resistance of the adhesive agent. Particularly, the CVD gas flow becomes slower at the bottom portions of the through holes than in the substrate surface, and therefore, degradation in the insulating film quality is conspicuous at the bottom portions. In a case where the TSV insulating films are made of a resin material, contact plugs are formed at the bottom portions of the through holes after the insulating films made of resin are formed, and the TSV electrodes are then formed. In this case, the insulating films made of resin deteriorate during the process of forming the contact plugs and the TSV electrodes, and the breakdown voltage of the TSV insulating films becomes lower. 
     To improve the breakdown voltage of TSV insulating films, isolation trenches that penetrate through a silicon substrate and surround respective TSV electrodes are formed, and insulating films are formed in the isolation trenches before devices and the TSV electrodes are formed in the silicon substrate. By this manufacturing method, Si-based insulating films are formed in the isolation trenches in the following manner. That is, after the isolation trenches are formed, polysilicon films are formed on the inner walls of the isolation trenches, and the polysilicon films are modified into SiO 2  films by thermal oxidation. In voids in the SiO 2  films, SiO 2  films are further formed by CVD. In this case, the type of the insulating films to be formed in the isolation trenches is selected by taking into account various kinds of load (such as heat history) of the device forming process and the through electrode forming process that follow the isolation trench forming process. 
     By using such a manufacturing method, the TSV insulating films still need to have sufficiently high heat resistance, and the options for the material of the insulating films are limited. Although the insulating films in the isolation trenches are Si-based insulating films, the width of each isolation trench needs to be made smaller to avoid voids, and therefore, processing the isolation trenches becomes difficult. Further, since the isolation trenches are filled with Si-based insulating films that are hard but fragile, there is a possibility that the isolation trench portions will crack when the thinned Si substrate is handled. Also, the process of forming the insulating films in the isolation trenches becomes complicated, resulting in higher manufacturing costs. 
     The inventors have made intensive studies, and have managed to develop radiation detectors and radiation detection apparatuses that are capable of improving the breakdown voltage of the TSV insulating films. Embodiments of the radiation detectors and the radiation detection apparatuses will be described below. 
     The following is a description of the embodiments, with reference to the accompanying drawings. However, it should be understood that the drawings are merely schematic, and the relationship between the thickness and the planar size of each component, and the width ratios between layers differ from those in reality. Therefore, specific thicknesses and sizes should be determined by taking into account the description below. Also, the relationships and ratios between components might vary among the drawings. 
     First Embodiment 
     A radiation detector according to this embodiment includes: a semiconductor substrate that has a first surface and a second surface located on the opposite side from the first surface; a light detecting unit placed on the side of the first surface of the semiconductor substrate; a first insulating film formed on the first surface to cover the light detecting unit; a second insulating film covering the first insulating film; a scintillator that is placed on the second insulating film and converts radiation into visible light; a first opening penetrating through the semiconductor substrate and the first insulating film; an interconnection that is placed between the first insulating film and the second insulating film, and is connected to the light detecting unit; a first electrode that is placed on the bottom surface and the side surface of the first opening and on part of the second surface, and is connected to the interconnection through a bottom portion of the first opening; a second electrode that is placed on the second surface of the semiconductor substrate having the light detecting unit formed therein, with the semiconductor substrate being divided by the first opening; a second opening that is formed in the semiconductor substrate, and is located in a region that surrounds the first electrode and does not surround the second electrode; and an insulating resin layer that covers the first electrode, the second electrode, the first opening, and the second opening in the second surface of the semiconductor substrate, and has a third opening and a fourth opening formed therein, the third opening leading to the first electrode, the fourth opening leading to the second electrode. 
     Referring to  FIGS. 1 through 3 , a radiation detector according to a first embodiment is described. As shown in  FIG. 3 , the radiation detector  10  of the first embodiment includes pixels  20  arranged in a matrix form on a semiconductor substrate (a semiconductor substrate  12  shown in  FIG. 1 ).  FIG. 3  shows a 5×5 pixel array. As shown in  FIG. 2 , each pixel  20  includes cells  21 , and those cells  21  are connected in parallel by an interconnection  30  made of aluminum, for example. The interconnection  30  is connected to a TSV electrode  44   a  provided for each pixel  20 . A bottom-surface electrode  44   b  is also provided for each pixel  20 .  FIG. 1  shows a cross-section of a region surrounding the TSV electrode  44   a.    
     As shown in  FIG. 1 , the radiation detector  10  of this embodiment includes light detecting units  22  contained in the respective cells  21  in one of the surfaces of the semiconductor substrate  12 . The light detecting units  22  are formed with avalanche photodiodes (hereinafter also referred to as APDs). An insulating film  24  made of SiO 2 , for example, is placed to cover those light detecting units  22 . Resistors  26  made of polysilicon, for example, are placed on the insulating film  24 . The resistors  26  are provided for the respective light detecting units  22 , and are designed to extract the characteristics of the light detecting units  22 . An interlayer insulating film  28  formed with SiO 2  layers is placed to cover the resistors  26 . The interconnections  30  are placed on the interlayer insulating film  28 . The interconnections  30  are connected to the light detecting units  22  via contacts  29   a  formed in the interlayer insulating film  28  and the insulating film  24 , and are connected to the resistors  26  via contacts  29   b  and  29   c  formed in the interlayer insulating film  28 . That is, the light detecting units  22  are connected in series to the resistors  26  via the contacts  29   a ,  29   b , and  29   c , and the interconnections  30 . An insulating film  36  made of SiO 2 , for example, is placed to cover the interconnections  30 . A scintillator  70  that converts X-rays into visible light is placed on the insulating film  36  via an adhesive agent  60 . 
     Through holes  40  that lead to the interconnections  30  are formed in the surface (the bottom surface) of the semiconductor substrate  12  on the opposite side from the surface having the light detecting units  22  formed therein. The through holes  40  are provided for the respective pixels  20  in one-to-one correspondence. In each of the through holes  40 , a seed layer  42   a  that has a stack structure formed with conductive materials such as a Ti layer and a Cu layer is provided to cover the bottom surface and the side surface of the through hole  40 , and to extend onto the bottom surface of the semiconductor substrate  12 . The Ti layer is a barrier metal. The electrodes  44   a  made of Cu, for example, are provided to cover the seed layers  42 , so that the electrodes  44   a  serve as the TSV electrodes. Isolation trenches  46  are formed in the semiconductor substrate  12  so as to surround the respective through holes  40 . The isolation trenches  46  are designed to penetrate through the semiconductor substrate  12 , and reach the insulating film  24  in  FIG. 1 . With the isolation trenches  46 , the TSV electrode  44   a  of each pixel  20  is isolated from the cells  21  including the light detecting units  22 . Seed layers  42   b  are also formed in regions on the bottom surface of the semiconductor substrate  12  on the outer sides of the respective isolation trenches  46 , and electrodes  44   b  made of Cu, for example, are formed on the seed layers  42   b . The electrodes  44   b  serve as the bottom-surface electrodes. The bottom-surface electrodes  44   b  are the terminals for applying voltage to the semiconductor substrate  12 . An insulating film  50  made of resin is attached to the bottom surface of the semiconductor substrate  12  to cover the TSV electrodes  44   a , the bottom-surface electrodes  44   b , and the isolation trenches  46 . In the insulating film  50 , openings  50   a  leading to the TSV electrodes  44   a  and openings  50   b  leading to the bottom-surface electrodes  44   f  are formed. 
     In the radiation detector  10  having such a structure, when an X-ray enters the scintillator  70  from above in  FIG. 1 , the X-ray is converted into visible light by the scintillator  70 . The visible light then passes through the adhesive agent  60 , the insulating film  36 , the insulating film  28 , and the insulating film  24 , and is detected by the light detecting units  22 . The number of photons in the visible light released from the scintillator  70  is proportional to the energy of the radiation entering the scintillator  70 . Accordingly, the energy of radiation that has passed through a test subject can be measured by counting the number of photons in visible light released from the scintillator  70 . By utilizing this feature in a CT system or the like, a CT image or a color CT image can be obtained through energy discrimination. 
     In this embodiment, the pixels  20  each having cells  21  that include light detecting units  22  formed with APDs operating in Geiger mode and are arranged in parallel to the corresponding interconnection  30  are arranged in an array. An APD that operates in Geiger mode is a photodiode that generates a current pulse every time a photon enters the APD. In this embodiment, APDs  22  are arranged in parallel to the corresponding interconnection  30  in each pixel  20 . Accordingly, the number of photons that each pixel  20  fails to detect can be reduced. As the pixels  20  each having APDs  22  arranged in parallel are arranged in an array, a current pulse having a wave height proportional to the number of APDs that photons have entered can be obtained. By measuring the wave height of this pulse, the number of phones that have entered the radiation detector  10 , or the energy of the radiation that has entered the scintillator  70 , can be measured. 
     First Modification 
       FIG. 4  shows a radiation detector according to a first modification of the first embodiment. The radiation detector  10 A of the first modification is the same as the radiation detector  1  of the first embodiment shown in  FIG. 1 , except that an insulating film  41  that is made of SiO 2  and is formed by CVD (Chemical Vapor Deposition), for example, is further provided to cover the bottom surface of the semiconductor substrate  12  having the through holes  40  and the isolation trenches  46  formed therein, the seed layers  42   a  and  42   b  are formed to cover the insulating film  41 , and the TSV electrodes  44   a  and the bottom-surface electrodes  44   b  are formed on the seed layers  42   a  and  42   b , respectively. Openings corresponding to the bottom surfaces of the through holes  40  are formed in the insulating film  41 , and the seed layers  42   a  are formed to cover the openings. 
     Second Modification 
       FIG. 5  shows a radiation detector according to a second modification of the first embodiment. The radiation detector  10 B of the second modification is the same as the radiation detector  1  of the first embodiment shown in  FIG. 1 , except that the bottom surfaces of the isolation trenches  46  reach the interconnections  30 . 
     Manufacturing Method 
     Referring now to  FIGS. 6(   a ) through  8 ( c ), a method of manufacturing the radiation detector  10  of the first embodiment is described. 
     First, as shown in  FIG. 6(   a ), the light detecting units  22  formed with APDs are formed in one of the surfaces of the Si substrate  12 . The Si substrate  12  may be a 725-μm thick Si substrate, for example. The insulating film  24  is formed to cover the one surface of the Si substrate  12  in which the light detecting units  22  formed with APDs are formed. The resistors  26  made of polysilicon are formed on the insulating film  24 . The interlayer insulating film  28  formed with SiO 2  layers is then formed to cover the resistors  26 . Openings leading to the light detecting units  22  and the resistors  26  are formed in the interlayer insulating film  28  and the insulating film  24 , and the openings are filled with a conductive material such as aluminum or tungsten, to form the contacts  29   a ,  29   b , and  29   c . The interconnections  30  made of aluminum, for example, are then formed on the interlayer insulating film  28 , and are connected to the contacts  29   a ,  29   b , and  29   c . At this point, the light detecting units  22  are connected in series to the resistors  26  via the contacts  29   a ,  29   b , and  29   c , and the interconnections  30 . The insulating film  36  made of SiO 2 , for example, is then formed on the interlayer insulating film  28  to cover the interconnections  30 . 
     As shown in  FIG. 6(   b ), support glass  84  that is a transparent supporting member and the Si substrate  12  are bonded by using an adhesive agent  82 . The thickness of the support glass  84  is 500 μm, for example. 
     After that, as shown in  FIG. 6(   c ), the Si substrate  12  is polished and thinned to a thickness of approximately 40 μm to 100 μm, with the support glass  84  serving as the supporting member. 
     As shown in  FIG. 7(   a ), the positions of the Si substrate  12  and the support glass  84  are reversed. In the positions in the bottom surface of the semiconductor substrate  12  in which the TSV electrodes  44   a  are to be formed, the through holes  40  are formed by RIE (Reactive Ion Etching). At this point, the bottom portions of the through holes  40  reach the interconnections  30 . The interconnections  30  also serve as the etching stopper for the RIE. 
     As shown in  FIG. 7(   b ), the isolation trenches  46  are formed to surround the respective through holes  40  by RIE. The bottom portions of the isolation trenches  46  penetrate through the Si substrate  12 . After penetrating through the Si substrate  12 , the isolation trenches  46  may be etched into part of the insulating film  24 . Alternatively, the isolation trenches  46  may reach the interconnections  30  like the through holes  40 , as in the second modification shown in  FIG. 5 . The width of each isolation trench  46  (the length in the horizontal direction in the drawing) is 5 μm to 50 μm. 
     As shown in  FIG. 7(   c ), the seed layers of the stack structure are then formed by stacking a Ti layer and a Cu layer by sputtering, to cover the bottom surfaces and the side surfaces of the respective through holes  40 , and the bottom surface of the semiconductor substrate  12 . After that, a Cu film, for example, is formed on the seed layers by an electrolytic plating process. Here, the Cu plating is not of a filling type for completely filling the through holes  40 , but of a non-filling type (a conformal type). In a later stage, the concave portions of the through holes  40  are filled with the insulating film  50  made of resin. By patterning the seed layers and the Cu film, the seed layers  42   a  and the TSV electrodes  44   a  are formed on the bottom surfaces and the side surfaces of the through holes  40 , and on part of the bottom surface of the semiconductor substrate  12 , and the seed layers  42   b  and the bottom-surface electrodes  44   b  are formed in regions on the bottom surface of the semiconductor substrate  12  on the outer sides of the isolation trenches  46 . 
     As shown in  FIG. 8(   a ), the insulating film  50  made of resin is then formed on the bottom surface of the semiconductor substrate  12 , to cover the TSV electrodes  44   a  and the bottom-surface electrodes  44   b . The openings  50   a  and the openings  50   b  that lead to the TSV electrodes  44   a  and the bottom-surface electrodes  44   b , respectively, are then formed in the insulating film  50 . The insulating film  50  may be a photosensitive solder resist, for example. In this case, after a photosensitive solder resist coat is formed, exposure and development are carried out with the use of a predetermined photomask, to form the insulating film  50  having the openings  50   a  and  50   b . Alternatively, the insulating film  50  may be formed with non-photosensitive insulating resin (such as epoxy resin or acrylic resin). In that case, after a non-photosensitive insulating resin coat is formed, a resist mask in a predetermined pattern is formed on the non-photosensitive insulating resin coat. The insulating resin is then patterned by etching, to form the insulating film  50  having the openings  50   a  and  50   b.    
     After that, as shown in  FIG. 8(   b ), the support glass  84  is detached from the semiconductor substrate  12 . At this point, the adhesive agent  82  is also detached from the insulating film  36 . 
     Lastly, as shown in  FIG. 8(   c ), the adhesive agent  60  is applied onto the insulating film  36 , and the scintillator  70  and the Si substrate  12  are then bonded. As a result, the radiation detector  10  shown in  FIG. 1  is completed. The scintillator  70  may be made of a material such as LGSO ((Lu,Gd) 2 SiO 5 ) or LYSO (Cerium doped Lutetium Yttrium Orthosilicate). The adhesive agent  60  has such a degree of transparency as to transmit visible light generated from the scintillator  70 . The thickness of the adhesive agent  60  is approximately 10 μm to 100 μm. 
     By the above described manufacturing method, the isolation trenches  46  are formed, so that the breakdown voltage of the TSV insulating film  50  or the breakdown voltage between the TSV electrodes  44   a  and the bottom-surface electrodes  44   b  can be dramatically improved. Also, as the through holes  40  and the isolation trenches  46  are filled with the insulating resin  50 , wafer breakage can be prevented by virtue of the mechanical strength and the appropriate elastic effect of the resin when the thinned Si substrate  12  is handled. If the isolation trenches  46  are made wider to improve the processability of the isolation trenches  46 , the isolation trenches  46  can be easily filled with the insulating resin  50 . Accordingly, the isolation trenches  46  can be easily processed. Furthermore, as the insulating resin  50  to fill the through holes  40  and the isolation trenches  46  is integrally formed, the manufacturing process can be simplified, and the manufacturing costs can be lowered. 
     According to the first embodiment and the modifications thereof, a radiation detector that can improve the breakdown voltage of the TSV insulating film can be obtained. 
     Second Embodiment 
       FIG. 9  is a cross-sectional view of a radiation detector according to a second embodiment. The radiation detector  10 C of the second embodiment is the same as the radiation detector  10  of the first embodiment shown in  FIG. 1 , except that insulating layers  63   a  and  63   b  made of SiN are formed on the regions of the insulating film  36  corresponding to the regions in which the through holes  40  and the isolation trenches  46  are formed. These insulating layers  63   a  and  63   b  can compensate for the decrease in the strength of the Si substrate  12  that is thinned in order to form the through holes  40  and the isolation trenches  46 . 
     This second embodiment can achieve the same effects as those of the first embodiment. The first modification or the second modification of the first embodiment may also be applied to the radiation detector of the second embodiment. 
     Third Embodiment 
       FIG. 10  is a cross-sectional view of a radiation detector according to a third embodiment. The radiation detector  10 D of the third embodiment is the same as the radiation detector  10  of the first embodiment shown in  FIG. 1 , except that the support glass  84  is placed between the insulating film  36  and the scintillator  70 , and the support glass  84  is bonded to the insulating film  36  with the adhesive agent  82  and is bonded to the scintillator  70  with an adhesive agent  68 . 
     Referring now to  FIGS. 11(   a ) and  11 ( b ), a method of manufacturing the radiation detector  10 D of the third embodiment is described. Prior to and in the step shown in  FIG. 8(   a ), the radiation detector  10 D is manufactured in the same manner as in the first embodiment. Although the support glass  84  is detached from the semiconductor substrate  12  in the first embodiment, the support glass  84  is thinned ( FIG. 11(   a )) after the openings  50   a  and the openings  50   b  that lead to the TSV electrodes  44   a  and the bottom-surface electrodes  44   b , respectively, are formed in the insulating film  50  made of resin ( FIG. 8(   a )). This thinning is performed by polishing and etching. The thickness of the support glass  84  is reduced from 500 μm to a thickness between 50 μm and 150 μm, for example. 
     Lastly, as shown in  FIG. 11(   b ), the scintillator  70  is bonded to the thinned support glass  84  with the adhesive agent  68 . As a result, the radiation detector  10 D shown in  FIG. 10  is completed. The scintillator  70  may be made of a material such as LGSO ((Lu,Gd) 2 SiO 5 ) or LYSO (Cerium doped Lutetium Yttrium Orthosilicate). Each of the adhesive agents  68  and  82  needs to have such a degree of transparency as to transmit visible light generated from the scintillator  70 . The thicknesses of the adhesive agents  68  and  82  are approximately 10 μm to 100 μm. 
     The third embodiment can also achieve the same effects as those of the first embodiment. Furthermore, having the support glass  84 , the radiation detector  10 D of the third embodiment has a higher strength than that of the radiation detector  10  of the first embodiment. Accordingly, breakage can be more effectively prevented when the radiation detector is handled. 
     As described so far, according to the first through third embodiments and the modifications thereof, isolation trenches penetrating through the semiconductor substrate are formed so as to surround the TSVs. Accordingly, the breakdown voltage of the TSV insulating film (the breakdown voltage between the TSV electrodes and the bottom-surface electrodes) can be dramatically improved. 
     Also, as the through holes and the isolation trenches in the TSV electrode portions are filled integrally with insulating resin, wafer breakage can be prevented by virtue of the mechanical strength and the appropriate elastic effect of the resin when the thinned Si substrate is handled. If the isolation trenches are made wider to improve processability of the isolation trenches, the isolation trenches can be easily filled with insulating resin. Accordingly, the isolation trenches can be easily processed. Furthermore, as the insulating resin to fill the through holes and the isolation trenches is integrally formed, the manufacturing process can be simplified, and the manufacturing costs can be lowered. 
     The first modification or the second modification of the first embodiment may be applied to the radiation detector of the third embodiment. Also, the third embodiment may be applied to the second embodiment. 
     Fourth Embodiment 
     Referring to  FIGS. 12(   a ) through  12 ( c ), the structure of a radiation detection apparatus according to a fourth embodiment is described.  FIG. 12(   a ) is a cross-sectional view of the structure of the radiation detection apparatus  500  of the fourth embodiment. 
     As shown in  FIG. 12(   a ), the radiation detection apparatus  500  includes a radiation tube  520 , radiation detecting units  510  placed on the opposite side from the radiation tube  520 , and a signal processing unit  580 . 
     The radiation tube  520  is a device that emits a radiation beam  530  such as an X-ray in a fan-like shape toward the radiation detecting units  510  located on the opposite side. The radiation beam  530  emitted from the radiation tube  520  passes through a test subject  540  on a stand (not shown), and enters the radiation detecting units  510 . 
     Each of the radiation detecting units  510  is a device that has an incident surface  221  to receive the radiation beam  530  that has been emitted from the radiation tube  520  and partially passed through the test subject  540 , converts the radiation into visible light, and detects the visible light as an electrical signal. The radiation detection apparatus  500  includes the radiation detecting units  510  arranged in an arc-like shape, a collimator  550  placed on the side of the incident surfaces  221  of the radiation detecting units  510 , and the signal processing unit  580  connected, by signal lines  150 , to electrodes on the opposite side of the respective radiation detecting units  510  from the radiation tube  520 . 
     The radiation detecting units  510  convert the radiation (the radiation beam  530 ) entering from the incident surfaces  221  into visible light, and converts (photoelectrically converts) the visible light into electrical signals (currents) with photoelectric conversion elements  114  described later. 
     The collimator  550  is an optical system that is placed on the side of the incident surfaces  221  of the radiation detecting units  510 , and refracts radiation so as to enter the radiation detecting units  550  in a collimated manner. 
     The signal processing unit  580  receives the electrical signals (currents) photoelectrically converted by the respective radiation detecting units  510  via the signal lines  150 , and calculates, from the current values, the energy of the radiation that has entered the respective radiation detecting units  510 . From the energy of the radiation that has entered the respective radiation detecting units  510 , the signal processing unit  580  generates a radiation image that is colored in accordance with the substances in the test subject  540 . 
     The radiation tube  520  and the radiation detecting units  510  are designed to rotate about the test subject  540 . With this arrangement, the radiation detection apparatus  500  can generate a cross-sectional image of the test subject  540 . 
     The radiation detection apparatus  500  according to this embodiment can be used not only for generating cross-sectional images of human bodies, animals, or plants, but also as an inspection apparatus such as a security screening apparatus for fluoroscopically inspecting objects. 
     Referring now to  FIGS. 12(   b ) and  12 ( c ), the radiation detecting units  510  and the structure thereof are described.  FIG. 12(   b ) shows the arrangement of the radiation detecting units  510  arranged in an arc-like shape.  FIG. 12(   c ) schematically shows the structure of the radiation detector  10  of one radio detecting unit  510 . 
     As shown in  FIG. 12(   b ), the radiation detecting units  510  are arranged in an arc-like shape, and the collimator  550  is placed on the radiation incident surface sides. As shown in  FIG. 12(   c ), in a radiation detecting unit  510 , a radiation detector  10  is secured onto a device supporting panel  200 . The radiation detector  10  includes a photoelectric conversion layer  110  having photoelectric conversion elements  114  arranged therein, and a scintillator  210  that converts radiation into scintillation light. The photoelectric conversion layer  110  and the scintillator  210  form a stack structure, with the incident surface side of the photoelectric conversion layer  110  being bonded to the emission surface side of the scintillator  210  with an adhesive layer. 
     The scintillator  210  includes light reflection layers  215  that are formed at predetermined pitch in two directions perpendicular to each other. The photoelectric conversion layer  110  and the scintillator  210  are divided, by the light reflection layers  215 , into photoelectric conversion components  220  arranged in a matrix form. The photoelectric conversion components  220  include photoelectric conversion elements  114 , and energy of incident radiation is detected by each photoelectric conversion component  220 . 
     In the radiation detection apparatus  500  shown in  FIGS. 12(   a ) through  12 ( c ), the radiation detectors  510  are radiation detectors according to one of the first through third embodiments and the modifications thereof. The photoelectric conversion elements  114  are equivalent to the pixels  20  described in the first through third embodiments. 
     According to the fourth embodiment, a radiation detection apparatus that includes radiation detectors capable of improving the breakdown voltage of the TSV insulating films can be obtained. 
     The radiation detectors of the first through third embodiments and the modifications thereof, and the radiation detection apparatus of the fourth embodiment can be used not only for obtaining cross-sectional images of human bodies, animals, or plants, but also in various kinds of inspection apparatuses such as security screening apparatuses for fluoroscopically inspecting objects. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.