1. Field of the Invention
The present invention relates to a radiation detecting apparatus and a radiation detecting system that are applied to a medical image diagnosing apparatus, a non-destructive inspection instrument, an analyzing apparatus using radiation, or the like.
2. Description of the Related Art
In recent years, thin film semiconductor manufacturing technology has been used for the manufacture of image pickup apparatuses and radiation imaging apparatuses. In particular, thin film semiconductor manufacturing technology has been used to manufacture image pickup apparatuses and radiation imaging apparatuses that include switching devices such as TFTs (thin film transistors) and conversion elements such as photoelectric conversion elements. Japanese Patent Laid-Open No. 2001-330677 proposes a radiation detector including a sensor base member having at least a plurality of photoelectric conversion elements on the side irradiated with X-rays emitted from an X-ray source and a scintillator provided on the side opposite from the side irradiated with X-rays. There is also disclosed in Japanese Patent Laid-Open No. 2001-330677 a configuration in which an entire surface of the sensor substrate or only a photoelectric converter on the sensor substrate is thinned by etching, thereby inhibiting radiation from being absorbed into the sensor substrate and improving light-receiving sensitivity and MTF (Modulation Transfer Function).
In Japanese Patent Laid-Open No. 2001-330677, the light receiving sensitivity and MTF are allegedly improved by etching only the photoelectric convertor on the sensor substrate. However, the strength of the radiation detecting apparatus is not considered at all, and hence there is room for improvement. Also, the photoelectric converter in Japanese Patent Laid-Open No. 2001-330677 is not clearly described.
The prevent invention provides a high-resolution, high-strength radiation detecting apparatus including a substrate, a photoelectric conversion element, and a scintillator arranged in this order from the side the radiation enters.
The invention provides a radiation detecting apparatus including a scintillator configured to convert radiated radiation into visible radiation, a plurality of photoelectric conversion elements configured to convert the visible radiation converted by the scintillator into charges, and a substrate having a first surface on which the scintillator and the photoelectric conversion elements are arranged and a second surface opposite from the first surface, in which the substrate, the photoelectric conversion elements, and the scintillator are arranged in this order from the side of the radiation detecting apparatus where the radiation enter, and the second surface includes a plurality of depressions arranged in areas opposite from areas of the first surface where the photoelectric conversion elements are arranged and a plurality of projections positioned between the plurality of depressions, in which at least parts of the projections are positioned in the opposite area.
There is also provided a radiation detecting system including the radiation detecting apparatus described above, a signal processing unit configured to process signals from the radiation detecting apparatus, a recording unit configured to record the signals from the signal processing unit, a display unit configured to display the signals from the signal processing unit, and a transmission processing unit configured to transmit the signals from the signal processing unit.
The invention also provides a method of manufacturing a radiation detecting apparatus, the radiation detecting apparatus including a substrate including a first surface having a plurality of photoelectric conversion elements configured to convert visible radiation converted from radiated radiation by a scintillator into charges and a second surface opposite from the first surface, in which the substrate, the photoelectric conversion elements, and the scintillator are arranged in this order from the side of the radiation detecting apparatus where radiation enters. The method includes forming a plurality of depressions and a plurality of projections positioned between the plurality of depressions in the second surface by applying a selective thinning process to the substrate from the side of the second surface of the substrate. The plurality of depressions has been formed in areas opposite from areas of the first surface where the plurality of photoelectric conversion elements are arranged, or areas of the first surface where the plurality of photoelectric conversion elements are arranged. At least parts of the projections positioned between the plurality of depressions are formed in the opposite areas.
Accordingly, the invention provides the high-resolution, high strength radiation detecting apparatus having the substrate, the photoelectric conversion elements, and the scintillator in this order from the side where the radiation enters.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Referring now to the attached drawings, the embodiments of the invention will be described in detail. In this specification, the term “radiation” includes high energy particle radiation, such as α rays, β rays, and γ rays which are beams generating particles (including photons) emitted by radioactive decay, but radiation also refers to X-rays or corpuscular rays, and cosmic rays. The term “visible radiation” generally refers to radiation in the electromagnetic spectrum ranging from ultraviolet to near infrared, that is ranging from about 380 nanometers to 760 nanometers.
Referring now to
As shown in
The flexible wiring board and the printed circuit board are provided with various integrated circuits. Examples of the integrated circuit include a drive circuit 110, a reading circuit 112, a power circuit 119, and a control circuit (not shown) described later. A scintillator 4 is fixedly arranged on the surface (first surface) opposite from the surface (second surface) on the side of the photoelectric converter 3 where the radiation enters. In other words, the scintillator 4 is arranged so as to oppose the first surface of the substrate 2. The second surface of the scintillator 4 is fixedly arranged on the first surface of the photoelectric converter 3 by vapor deposition, or by adhesion. A first surface of the scintillator 4 is fixed to a second surface of the supporting base 9 installed on a housing 8 via an adhesive agent, a viscous agent, a shock absorbing material or the like. The printed circuit boards 7a and 7b are arranged on the side of a first surface of the supporting base 9. Accordingly, in the radiation detecting apparatus 1 of the invention, the substrate 2, the photoelectric converter 3, and the scintillator 4 are arranged in this order from the side of the radiation detecting apparatus 1 irradiated with the radiation.
A cover 5 is arranged on the housing 8 on the side where the radiation is incident upon (enters) the radiation detection apparatus. In this manner, an enclosure is formed by the housing 8 and the cover 5. The cover 5 allows for easy passage of radiation and has water-resistant properties and sealing properties. The substrate 2, the photoelectric converter 3, the scintillator 4, the flexible wiring board 6, and the printed circuit boards 7a and 7b are fixed to the supporting base 9 and accommodated in the enclosure formed by the housing 8 and the cover 5. The printed circuit boards 7a and 7b are arranged on the side of the second surface of the supporting base 9, so that an adverse effect of the radiation on the integrated circuit is reduced. In this manner, with the configuration in which the depressions 2a are provided on the second surface of the substrate 2 in areas corresponding the areas of the first surface where the photoelectric conversion elements are arranged, the thickness of the substrate 2 in the area where the photoelectric conversion elements are arranged is reduced in comparison with the substrate where the depressions 2a are not provided, whereby the amount of radiation passing through the substrate 2 is increased. Also, since the radiation passing through the substrate 2 is increased in comparison with the substrate having no depressions 2a, the amount of light emission of the scintillator 4 is increased and the amount of visible radiation irradiated on the photoelectric converter 3 is increased correspondingly, which leads to an improvement in the sensitivity. In addition, since the distance between the position at which light is emitted from the scintillator 4 and the photoelectric converter 3 is short, scattering of visible radiation is inhibited and MTF (sharpness) is improved.
Examples of the substrate 2 include a glass substrate, a silicon substrate, and a hard carbon substrate having heat-resistant properties with respect to the process temperature for the formation of the photoelectric converter 3. Substrates manufactured by forming an organic or inorganic insulation film on the surface of the substrate material may be used as the substrate 2. Examples of the insulating film which may be used include inorganic insulating films such as a silicon oxide film or a silicon nitride film, or organic insulating films such as PET (polyethylene terephthalate) or PI (polyimide). It is also possible to form depressions and projections on the second surface of the substrate 2 after the formation of the photoelectric converter 3 so as to achieve a suitable thickness by thinning the surface of the substrate material on the side where the radiation enters partly by etching or CMP. Also, a substrate having a predetermined thickness having been formed with depressions and projections in advance by molding may be prepared. In this manner, by using the substrate 2 having partly thinned areas, the amount of radiation passing through the substrate 2 is increased. Here, when applying a thinning process on the substrate material after the scintillator 4 has been fixedly arranged on the first surface of the photoelectric converter 3, a protective material may be arranged on the side of the front surface of the scintillator 4. It is because the shape may be deformed when vibrations are applied on a phosphor layer in a case where particle phosphor such as GD2O2S:Tb is used in the phosphor layer used in the scintillator 4. The same applies to a case where an alkali column crystalline structure such as CsI:Tl or CsI:Na is used in the phosphor layer. Therefore, it is desirable to arrange some sort of protective material on a first surface of the scintillator 4 arranged on the side opposite from the second surface of the substrate 2. A thinning process may further be performed on the protective material. The protective material may be the same material as the substrate 2 or, alternatively, the protective material may be used as part of the supporting base 9.
Referring now to
An operation of the radiation detecting apparatus according to the first embodiment will be described below. The reference potential Vref is applied to the first electrodes 103 of the photoelectric conversion elements 104 via switching devices 105, and the bias potential Vs is applied to the second electrodes 102, whereby a bias which depletes the photoelectric conversion layer of the MIS photoelectric conversion element is applied to the photoelectric conversion elements 104. In this state, a subject is irradiated with radiation in test. The radiation passes through the subject while being attenuated therein, and is converted into visible radiation by the scintillator 4. This visible radiation enters the photoelectric conversion elements 104 and is converted into charges. Electric signals corresponding to the charges are output to the signal lines 108 when the switching devices 105 are brought into a conductive state by drive pulses applied from the drive circuit 110 to the drive lines 107 and are read to the outside by the reading circuit 112 as digital data. Subsequently, the switching devices 105 are brought into a conductive state by changing the potential of the bias lines 106 from the bias potential Vs to the initialization potential Vr, so that positive or negative carriers generated in the photoelectric conversion elements 104 and remaining therein are eliminated. Subsequently, the potential of the bias lines 106 is changed from the initialization potential Vr to the bias potential Vs, so that initialization of the photoelectric conversion elements 104 is achieved.
Referring now to
First conductive layers 201, a first insulating layer 202, first semiconductor layers 203, first impurity semiconductor layers 204, and second conductive layers 205 are arranged in sequence on the first surface of the substrate 2. Here, the first conductive layers 201 constitute control electrodes of the switching devices 105 and the drive lines 107, the first insulating layer 202 constitute gate insulating films of the switching devices 105, and the first semiconductor layers 203 constitute channels of the switching devices 105. The first impurity semiconductor layers 204 become ohmic contacts of the switching devices 105, and the second conductive layers 205 become two main electrodes and the signal lines 108 of the switching devices 105. Second insulating layers 206 are arranged between the switching devices 105 and the photoelectric conversion elements 104. The second insulating layers 206 function as insulating interlayers. Third conductive layers 207 which become the first electrodes 103 of the photoelectric conversion elements 104 are electrically coupled to the second conductive layers 205 which become the first main electrodes of the switching devices 105 via through holes provided in the second insulating layers 206. The third conductive layers 207, third insulating layers 208, second semiconductor layers 209, second impurity semiconductor layers 210, fourth conductive layers 211, and fifth conductive layers 212 are arranged in sequence on the second insulating layers 206 on the opposite side from the substrate 2. Here, the third insulating layers 208 become complete insulating layers, the second semiconductor layers 209 become photoelectric conversion layers, the second impurity semiconductor layers 210 become hole blocking layers, the fourth conductive layers 211 become the second electrodes 102 of the photoelectric conversion elements 104, and the fifth conductive layers 212 become the bias lines 106. Although the third insulating layers 208 are employed in this embodiment because the MIS photoelectric conversion elements 104 are employed, the invention is not limited thereto. When PIN photodiodes are employed as the photoelectric conversion elements 104, third impurity semiconductor layers which function as electron blocking layers may be employed instead of the third insulating layers 208. In this case, the hole blocking layers and the electron blocking layers may be interchanged. The plurality of photoelectric conversion elements 104 are covered with fourth insulating layers 213 which serve as passivation films, and the scintillator 4 (not shown) is provided above fifth insulating layers 214 which function as planarizing layers provided on the fourth insulating layers 213. Here, the width P1 of the photoelectric conversion element 104 in the invention is defined by the width of the third conductive layer 207 which becomes the first electrode 103 of the photoelectric conversion element 104. The width P2 between adjacent ones of the photoelectric conversion elements 104 is defined by the width between the third conductive layers 207.
The substrate 2 is partly removed from the second surface side thereof, and hence has the plurality of depressions 2a and projections 2b. The depressions 2a are positioned in areas of the second surface of the substrate 2 which are opposite the areas of the first surface of the substrate 2 where the photoelectric conversion elements 104 are arranged and have a width indicated by P3. In other words, the depressions 2a are positioned in areas on the second surface of the substrate 2 where the plurality of photoelectric conversion elements 104 is orthogonally projected from the side of the scintillator 4 in the direction vertical to the substrate 2 (the orthogonal projection areas of the photoelectric conversion elements 104). In the invention, the orthogonal projection areas of the photoelectric conversion elements 104 mean areas on the second surface of the substrate 2 where the orthogonal projections of the first electrodes 103 of the photoelectric conversion elements 104 are positioned. The projections 2b are each positioned between adjacent ones of the plurality of depressions 2a on the second surface of the substrate 2, and the width is indicated by P4. Here, the depressions 2a in the invention are areas having a thickness of 50% or smaller of the thickness of the thickest portions of the projections 2b, and the width P3 of the depressions 2a is defined by the width of the areas having a thickness of 50% or smaller. The projections 2b are areas having a thickness of 50% or larger of the thickest portions of the projections 2b, and the width P4 is defined by the width between the adjacent projections 2b. In this manner, owing to the positioning of the depressions 2a in the areas on the second surface of the substrate 2 which are opposite the areas of the first surface of the substrate 2 where the photoelectric conversion elements 104 are arranged, the amount of radiation passing through the substrate 2 is increased, and hence the radiation detecting apparatus with a higher sensitivity is provided.
In the invention, parts of the projections 2b are positioned within the areas on the second surface of the substrate 2 opposite from the areas where the photoelectric conversion elements 104 are arranged, and the remaining portions of the projections 2b other than the parts described above are positioned between the areas on the second surface of the substrate 2 opposite from the areas where the photoelectric conversion elements 104 are arranged. In other words, parts of the projections 2b are each positioned on the second surface of the substrate 2 within the area of each of the orthogonal projection areas of the photoelectric conversion elements 104, and the remaining portions other than the parts are each positioned on the second surface between adjacent ones of the areas of the orthogonal projection areas of the photoelectric conversion elements 104. In this embodiment, the projections 2b each lie on the second surface of the substrate 2 astride the area opposite a portion positioned between adjacent one of the photoelectric conversion elements 104 and the area where each of the photoelectric conversion elements 104 is arranged. In other words, the width P3 of the depressions 2a is smaller than the width P1 of the photoelectric conversion elements 104, and the width P4 of the projections 2b is larger than the width P2 between the photoelectric conversion elements 104. In this embodiment, the projections 2b are arranged in a reticular pattern, which further improves the mechanical strength of the substrate 2. In this structure, even when the depressions are provided on the second surface of the substrate 2 corresponding to the photoelectric conversion elements 104 for increasing the amount of passage of the radiation, the strength of the substrate 2 is secured in a wider area. The substrate strength is particularly secured when, as shown in
The material of the substrate 2 is not necessarily formed of one kind of substrate material. For example, as shown in
Referring now to
As shown in
Subsequently, as shown in
A case where the first substrate 221 and the second substrate 222 shown in
In the first embodiment, the process in which the substrate 2 having the photoelectric converter 3 and the scintillator 4 arranged thereon is thinned is described. However, the invention is not limited thereto. The scintillator 4 may be formed after the thinning process of the substrate 2, and the photoelectric converter 3 may also be formed after the thinning of the substrate 2. However, a state in which the photoelectric converter 3 is arranged on the first surface of the substrate 2 is more suitable because the alignment with respect to the photoelectric converter 3 is easier.
In this embodiment, the shape of the depressions 2a have been described to have a rectangular shape including two sides parallel to the drive lines 107 and two sides parallel to the signal lines 108, that is, a rectangular shape including four sides parallel to the sides of the first electrode 103 of the photoelectric conversion element 104. However, the invention is not limited thereto. For example, the depressions may have a polygonal shape (for example, a rectangular shape) having a side which is not parallel to the drive lines 107 and the signal lines 108, that is, having at least one side which is not parallel to side of the first electrode 103 of the photoelectric conversion element 104 as shown in
If the photoelectric converter 3 has the stacked structure in which the switching devices 105 are arranged between the photoelectric conversion elements 104 and the substrate 2 so as to be covered with the photoelectric conversion element 104, at least parts of the projections 2b are suitably positioned on the second surface of the substrate 2 within the orthogonal projection areas of the switching devices 105. Accordingly, the mechanical strength of the substrate 2 is further increased, and the radiation detecting apparatus with higher strength is provided. Also, the depressions 2a are suitably arranged so that the projections 2b are positioned in the areas on the second surface opposite from the first surface of the substrate 2 where the drive lines 107 and the signal lines 108 are arranged.
It is more suitable to provide a light absorbing layer 215 formed of a material having a high absorbancy with respect to the visible radiation converted by the scintillator 4 for absorbing the visible radiation on the second surface of the formed substrate 2. Accordingly, the light reflected in a scattered manner by the second surface having the depressions and projections of the substrate 2 is reduced, and hence the radiation detecting apparatus with higher sharpness is provided. The light absorbing layer 215 may be applied adequately to the configuration shown in
Referring now to
One depression 2a is provided correspondingly to one photoelectric conversion element 104 in the first embodiment. However, in the second embodiment, a plurality of (two, for example) depressions 2a are provided for one photoelectric conversion element 104. In other words, assuming that k is a natural number of two or larger, the pitch P3 of the depressions 2a is smaller than 1/k times the pitch P1 of the photoelectric conversion elements 104. With this configuration, the projections 2b are positioned such that the entire widths thereof are arranged in areas of the second surface of the substrate 2 which are opposite the areas of the first surface of the substrate 2 where the photoelectric conversion elements 104 are arranged. Accordingly, the mechanical strength of the substrate 2 is further increased, and the radiation detecting apparatus with higher strength is provided. Also, accordingly, a pseudo low-pass filter is inserted spatially, and hence the radiation detecting apparatus with higher sharpness with reduced moiré fringes is provided. Since the first embodiment corresponds to a case where k=1, the pitch P3 of the depressions 2a is desirably smaller the 1/k times the pitch P1 of the photoelectric conversion elements, where k is a natural number of 1 or larger in the invention. The configuration in the second embodiment may also be applied adequately to a polygon (for example, rectangle) having a plurality of sides which are not parallel to the drive lines 107 and the signal lines 108 as shown in
Referring now to
One or more depressions 2a are provided correspondingly to one photoelectric conversion element 104 in the first and second embodiments. However, in the third embodiment, one depression 2a is provided astride a plurality of photoelectric conversion elements 104 (four in two rows and two columns, for example). In other words, assuming that k is a natural number of one or larger, the pitch P3 of the depressions 2a is not smaller than k times the pitch P1 of the photoelectric conversion elements 104. However, in such a case, in order to secure the mechanical strength of the substrate 2, the depressions 2a are suitably arranged so that the projections 2b are positioned in the areas on the second surface opposite from the areas on the first surface of the substrate 2 where the drive lines 107 and the signal lines 108 are arranged. Accordingly, assuming that k is a natural number of one or larger, required mechanical strength of the substrate 2 is secured even in a case where the pitch P3 of the depressions 2a is not smaller than k times the pitch P1 of the photoelectric conversion elements 104. Although an example has been described in the third embodiment in which one depression 2a is positioned in an area corresponding to the areas where four photoelectric conversion elements 104 are arranged on the first surface of the substrate 2, the invention is not limited thereto. Assuming that k is a natural number of two or larger, one depression 2a may be positioned in an area corresponding to the areas where the k photoelectric conversion elements 104 are arranged on the first surface of the substrate 2. However, it is desirable that the arrangement and the shape of the depressions 2a are determined so that the areas where the plurality of photoelectric conversion elements 104 are arranged equal to the overlapped area of the depression 2a. It is for equalizing the amount of radiation which passes each pixel.
The configuration in the third embodiment may also be applied adequately to a polygon (for example, a rectangle) having a plurality of sides which are not parallel to the drive lines 107 and the signal lines 108 as shown in
Referring now to
An X-ray 6060 generated in an X-ray tube 6050 passes through a chest portion 6062 of a patient or a test subject 6061, and enters a radiation detecting apparatus 6040 having the scintillator 4 arranged on the first surface of the photoelectric converter 3. The entered X-ray includes information on the test subject 6061 within the body. The scintillator 4 emits light corresponding to the entry of the X-ray, and the electrical information is obtained by converting the emitted light by the photoelectric converter 3. This information is converted into digital data, and is subjected to image processing by an image processor 6070 as a signal processing unit, thereby being displayed on a display 6080 as a display unit of the control chamber.
This information can be transmitted to distant places by a transmission processing unit such as a telephone circuit 6090, and can be displayed on the display 6081 as a display unit in a different place such as a doctor room or stored in a recording unit such as an optical disk, whereby doctors at the distant places are capable of diagnosing. It is also possible to record the information in a film 6110 which is recording medium by the film processor 6100 as a recording unit.
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. 2011-005952 filed Jan. 14, 2011, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2011-005952 | Jan 2011 | JP | national |