Patent Publication Number: US-8530848-B2

Title: Radiation-sensitive substrate

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Reference is made to commonly-assigned, co-pending U.S. patent application Ser. No. 13/214,550 filed concurrently herewith, entitled “METHOD OF MAKING A RADIATION-SENSITIVE SUBSTRATE” by Cok, the disclosure of which is incorporated herein. 
     FIELD OF THE INVENTION 
     The present invention relates to an apparatus for detecting radiation to form an image and in particular to substrates used for digital radiography. 
     BACKGROUND OF THE INVENTION 
     High-frequency radiation, such as x-rays, is widely used as diagnostic tools for human diseases and injuries. Radiation-sensitive substrates, such as x-ray film, are exposed to radiation that has passed through portions of the human body thereby forming images of internal structures in the body that have differentially absorbed the radiation. In digital radiographic systems, radiation-sensitive materials coated over a substrate and exposed to radiation form a charge pattern in the coated substrate that can form an image when read with electronic circuits. 
     Digital radiography can provide advantages in medical or other diagnostic work. For example, digital radiographs are reusable and do not require chemical development, thereby decreasing response time and costs. Digital radiography can also be more sensitive to radiation so that radiation exposure to human subjects is reduced. Despite these advantages, digital radiography is expensive and can suffer from electronic noise that reduces the accuracy of the read charge pattern, reducing its diagnostic value. 
     The radiation-sensitive substrates in digital radiographic systems form flat-panel detectors. In one type of system, substrates coated with photo-stimulable phosphors are exposed to radiation. The photo-stimulable phosphors are exposed to light to produce a signal whose strength corresponds to the amount of radiation exposure incident on the phosphors. After exposure, the plates are placed in a reader that stimulates the substrate with light, for example using a scanning laser, to retrieve the signal over the area of the substrate to produce an image. 
     In another type of flat-panel detector, a layer of scintillating material (e.g. cesium iodide or gadolinium oxysulfide) coated over a substrate responds to x-ray radiation by emitting photons in proportion to the quantity of incident radiation. The photons are then detected by amorphous silicon photo-diodes to produce a current that is electronically detected. The photo-diodes are distributed over the area of the substrate to provide multiple signals corresponding to pixels forming an image of the x-ray radiation that is used for diagnosis by a radiologist. 
     Yet another type of flat-panel detector uses a layer of radiation-sensitive material (e.g. amorphous selenium) coated over a substrate between electrodes that responds to x-ray radiation by forming a charge in proportion to the quantity of incident radiation. The charge forms a pattern corresponding to the incident radiation and is detected by electrodes patterned over the substrate that are connected to electronic circuits. Essentially, an array of capacitors are charged in a pattern corresponding to the radiation pattern and the capacitor charges are read with the electronic circuits to form pixel values forming an image of the x-ray radiation that is used for diagnosis by a radiologist. 
     It is preferable that any electronic signal produced from a digital radiographic exposure be read accurately and quickly. For large substrates, it is difficult to transfer an electronic signal to circuits separate from the radiation-sensitive substrate at high speed and without adding electronic noise, particularly for the signal-measuring circuitry. Furthermore, it is preferable that any substrate have as large a radiation-sensitive area as possible to provide as high-resolution a signal as possible, for example having as many pixels per unit area as possible. 
     U.S. Pat. No. 5,381,014 describes a large area x-ray image capture element fabricated by juxtaposing a plurality of discrete array modules in an assembly over the top surface of a base plate, such that each module is disposed adjacent at least one other module to form a two-dimensional mosaic of modules. Each of the discrete modules includes a plurality of thin-form transistors arrayed adjacent the top surface of a dielectric substrate wherein at least one precision-ground edge forms a precise abutment with a precision-ground edge of another substrate. A continuous radiation detecting layer is disposed over the plurality of juxtaposed modules and produces a latent radiographic image in the form of electrical charges. Such a method reduces or totally voids the non-radiation-detecting areas created at the borders between the array modules. However, such a design employs thin-film electronic devices that are known to have lower performance than crystalline semiconductor electronic devices. Furthermore, the assembly of the described structure is problematic. 
     The location of crystalline integrated circuits over a substrate such as a printed-circuit board is known in the prior art, for example using surface-mount integrated-circuit components, such as ball-grid arrays, multi-chip modules, and flip-chips, as well as soldering the components to the printed-circuit board. A variety of packaging and placement techniques, both manual and automated, are known for assembling electronically active substrates. Such integrated-circuit substrate structures, however, can interfere with the ability of a radiation-sensitive substrate to provide a high-resolution, low-noise, image of radiation incident on the substrate. 
     There is a need, therefore, for an alternative substrate design for providing a high-resolution, low-noise, image of patterned radiation incident on the substrate. 
     SUMMARY OF THE INVENTION 
     The need is met in one embodiment of the present invention by a radiation-sensitive apparatus, comprising: 
     a first substrate having an active side; 
     a radiation-sensitive layer formed over the active side of the first substrate; 
     a plurality of spatially separated integrated circuits located on the active side, each integrated circuit having:
         a second individual substrate different and separate from the first substrate;   one or more electronic circuit(s) formed in or on the second substrate; and   one or more electrode connection pads formed in or on the second substrate, each electrode connection pad electrically connected to at least one of the electronic circuit(s);       

     a plurality of pixel electrodes formed over the active side of the first substrate separate from the integrated circuit, each pixel electrode electrically connected to an electrode connection pad; 
     an electronic control circuit electrically connected to each electronic circuit in each integrated circuit; and wherein 
     the electronic circuits are responsive to electrical signals formed by the interaction of electromagnetic radiation and the radiation-sensitive layer, the electrical signals conducted by the pixel electrodes and electrode connection pads. 
     The present invention provides an improved radiation-sensitive substrate that forms high-resolution and low-noise images in response to patterned radiation exposure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross section of a top-detecting radiation-sensitive apparatus according to an embodiment of the present invention; 
         FIG. 2  is a cross section of an integrated circuit useful in various embodiments of the present invention; 
         FIG. 3  is a schematic of a radiation-sensitive apparatus according to an embodiment of the present invention; 
         FIG. 4  is a cross section of a bottom-detecting radiation-sensitive apparatus according to an alternative embodiment of the present invention; 
         FIG. 5  is a cross section of an alternative bottom-detecting radiation-sensitive apparatus according to another embodiment of the present invention; 
         FIG. 6  is a cross section of an alternative bottom-detecting radiation-sensitive apparatus having a protective layer according to yet another embodiment of the present invention; 
         FIG. 7  is a cross section of an alternative bottom-detecting radiation-sensitive apparatus having protective elements according to another embodiment of the present invention; 
         FIG. 8  is a schematic of a radiation-sensitive apparatus according to another embodiment of the present invention; 
         FIG. 9  is a schematic of a radiation-sensitive apparatus according to another embodiment of the present invention; 
         FIG. 10  is a cross section of a radiation-sensitive apparatus having segmented portions according to another embodiment of the present invention; 
         FIG. 11  is a flow graph illustrating an embodiment of the present invention; 
         FIG. 12  is a flow graph detail of a portion of  FIG. 11  illustrating an embodiment of the present invention; 
         FIG. 13A  is a plan view of a common electrode formed on the active side of the first substrate with segmented portions in a horizontal direction useful for understanding an embodiment of the present invention; 
         FIG. 13B  is a plan view of a common electrode formed on the active side of the first substrate with two-dimensional segmented portions useful for understanding an embodiment of the present invention; and 
         FIG. 14  is a flow graph illustrating an embodiment of the present invention. 
     
    
    
     Because the various layers and elements in the drawings have greatly different sizes in the various embodiments, the drawings are not to scale. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the cross section of  FIG. 1 , in one embodiment the present invention includes a radiation-sensitive apparatus  5  including a first substrate  10  having an active side  11 . A plurality of layers is formed over the active side  11  of the first substrate  10 . A layer formed over the active side  11  of the first substrate  10  is a layer formed on, over, or above the active side  11  of the first substrate  10  or on, over, or above another layer formed on, over, or above the active side  11  of the first substrate  10 . Thus, the plurality of layers located on, over, or above, the active side  11  of the first substrate  10  form a multi-layer structure on the active side  11  of the first substrate  10 . The layers are largely planar and extend over much, but not necessarily all, of the surface of the first substrate  10  and can be formed through a variety of techniques known in the art, for example by evaporative material deposition, sputtering, coating (e.g spin coating or blade coating) and drying, or by mechanically placing pre-formed elements in a common layer. The first substrate  10  can include any of a variety of materials, for example glass, metal, or plastic, and can be rigid or flexible. 
     A plurality of spatially separated integrated circuits  20  is located on the active side  11 . The integrated circuits  20  do not touch each other and are separated by a distance D greater than zero and are optionally located on an adhesive layer  12  in an approximately planar array in a layer. The adhesive layer  12  is optionally formed, for example, by liquid coating a curable resin adhesive on the first substrate  10 , as is known in the photolithographic arts, e.g. by spray, slot, or blade coating and the integrated circuits  20  placed on the adhesive layer  12 . As shown in  FIG. 2 , each integrated circuit  20  includes a second individual substrate  24  different and separate from the first substrate  10 . The substrate is optionally crystalline and can include or be made of semiconductor materials, such as silicon or gallium arsenide. Such materials, placement, and processing methods are known in the integrated circuit arts. An encapsulating and insulating layer  14  ( FIG. 1 ) (e.g. using a curable and patternable resin) is optionally formed over the integrated circuits  20  (e.g. by coating) and patterned (e.g. by patterned exposure, curing, and etching) to form openings (vias) through which electrical connections are made to the pixel and control connection pads  22 ,  28 . Such materials and processes are well-known in the integrated circuit and printed circuit board arts. 
     Referring to the  FIG. 2  integrated circuit cross section, the integrated circuits  20  include one or more electronic circuit(s)  26  formed in or on the second substrate  24 . One or more pixel connection pads  22  are formed in or on the second substrate  24 . Each pixel connection pad  22  is electrically connected to at least one of the electronic circuit(s)  26 . Control connection pads  28  connected to the electronic circuits  26  provide an electrical control interface to the integrated circuit  20 . Both the pixel connection pads  22  and the control connection pads  28  are electrode connection pads. The electronic circuits  26  are optionally conventional semiconductor circuits, either analog or digital, or both, that are capable of receiving, communicating, transmitting, or processing electrical signals. The electronic circuits  26  can include multiple, similar circuits each connected to a different pixel connection pad  22  for receiving, communicating, transmitting, or processing separate electrical signals conducted through a corresponding pixel connection pad  22 . The electronic circuits  26  can include photo-transistors, photo-capacitors, or amplifiers (e.g. transistor circuits) known in the art for receiving, controlling, and processing electrical signals. The integrated circuits  20  are optionally made in a separate process and at a different time from the radiation-sensitive apparatus  5  of the present invention. 
     Referring back to  FIG. 1 , a plurality of pixel electrodes  30  are formed over the active side  11  of the first substrate  10  and define pixels  70 . The pixel electrodes  30  are separate from the integrated circuit  20 , and are not formed on or in the integrated circuit  20  or electrical circuits  26  ( FIG. 2 ) but are formed over the first substrate  10  and electrically connected to the electrical circuits  26  ( FIG. 2 ) through a pixel connection pad  22 . The pixel electrodes  30  are optionally segmented and electrically separate from each other to carry separate and distinct electrical signals. Insulators  15  electrically insulate the pixel electrodes  30  from each other and can include such materials as silicon dioxide or cured photo-patterned resins. Such insulating structures and materials are well-known in the integrated circuit and electronic substrate arts and are patterned with well-known processes, such as coating photo-sensitive materials, pattern-wise curing the photo-sensitive materials with a patterned exposure, and etching. Likewise, the pixel electrodes  30  can be patterned using similar well-known photo-lithographic processes. 
     A radiation-sensitive layer  40  is formed over the active side  11  of the first substrate  10 . The radiation-sensitive layer  40  can be formed by deposition methods, such as vapor deposition or sputtering, that are known in the photo-lithographic and integrated circuit arts and can include one or more materials in a common layer. Alternatively, the radiation-sensitive layer  40  can further include sub-layers, each of which can be a different material or different combination of materials. Different sub-layers can have materials in common. 
     The radiation-sensitive layer  40  is responsive to incident radiation to form an electrical signal. Thus, at least one of the materials in the radiation-sensitive layer is sensitive to radiation. For example, the radiation can directly interact with the radiation-sensitive layer  40  to produce a change in the localized charge of the radiation-sensitive layer  40  or to produce a change in the local resistivity of the radiation-sensitive layer  40  (e.g. through changes in photo-conductivity) that is detected as an electrical signal. The specific material forming the radiation-sensitive layer  40  will depend upon the charge generation or charge transport properties desired in the radiation-sensitive layer  40  and its sensitivity to the desired type of radiation. In one non-limiting example, the radiation is x-ray radiation. In another non-limiting example, the radiation is light. 
     In another example, the electrical signal is indirectly produced. In this example, incident radiation (e.g. x-rays) interacts with at least one scintillating material in the radiation-sensitive layer  40  to cause secondary emission of a lower frequency radiation, for example, light. The light is then detected using conventional photo-sensing structures, such as photodiodes using silicon, that produce an electrical signal in response to the secondary light emission. In this embodiment, at least two materials are used in the radiation-sensitive layer  40 , a scintillating material and a light-responsive material. The arrangement, composition and layer thickness of such materials are known in the digital radiographic and the photo-sensing arts. 
     According to various embodiments of the present invention, different kinds of radiation-sensing materials are used and can take a variety of forms, such as amorphous, crystalline, or polycrystalline. Useful radiation-sensing materials include silicon, selenium, cadmium sulfide, mercuric iodide, or lead oxide and are deposited in a layer using methods known in the digital radiographic, photo-lithographic, and integrated circuit arts, for example evaporation, sputtering, or coating. The materials are doped, for example selenium is doped with arsenic and can form an alloy. 
     In a further embodiment of the present invention shown in  FIG. 1 , a common electrode  50  is formed over the radiation-sensitive layer  40 . The common electrode  50  can extend over much of the first substrate  10  and is co-extensive with the pixel electrodes  30 . By applying an electrical bias between the common electrode  50  and the pixel electrodes  30 , charge is moved or a current conducted to one or the other of the common or pixel electrodes  50  or  30  to form an electrical signal for each pixel electrode  30  that is conducted through the pixel connection pads  22  to the electronic circuits  26 . The common electrode  50  is electrically connected to an electronic control circuit  80  ( FIG. 3 ) or to the integrated circuits  20  (not shown). A protective layer  60  is optionally formed over the common electrode  50  to protect the various layers formed on the first substrate  10 . 
     Both the common electrode  50  and the pixel electrode  30  can comprise electrically conductive materials known in the art such as metal (e.g. aluminum, silver, gold), metal alloy, metal oxide (e.g. indium tin oxide, zinc aluminum oxide, tin oxide) or other conductors including inorganic or organic materials (e.g. carbon, carbon nanotubes in a binding layer, and polythiophene). Deposition methods for the various materials (e.g. vapor deposition, sputtering, or coating) are known in the art. The common electrode  50  is transparent to the incident radiation if the radiation-sensitive layer  40  is exposed through the common electrode  50 . If it is not, then the common electrode  50  is optionally opaque to the incident radiation. Similarly, the pixel electrodes  30  is transparent to the incident radiation if the radiation-sensitive layer  40  is exposed through the pixel electrodes  30 . If it is not, then the pixel electrodes  30  is optionally opaque to the incident radiation. 
     Referring to the schematic of  FIG. 3 , the radiation-sensitive apparatus  5  has an electronic control circuit  80  that is electrically connected to each electronic circuit  26  ( FIG. 2 ) in each integrated circuit  20  through electrical connectors  32  (e.g. wires formed on or over the first substrate  10  or layers on the first substrate  10 ) and control connection pads  28 . The electronic circuits  26  ( FIG. 2 ) are responsive to electrical signals formed by the interaction of electromagnetic radiation and the radiation-sensitive layer  40  ( FIG. 1 ), the electrical signals conducted by the pixel electrodes  30  and pixel connection pads  22 . The pixel electrodes  30  are electrically connected to pixel connection pads  22  through pixel connection wires  34 , as needed for a desired first substrate  10  layout. As shown in  FIG. 3 , pixels  70  are defined by the extent of each pixel electrode  30  in combination with the common electrode  50 . The common electrode  50  can also be connected to the electronic control circuit  80 . 
     The radiation-sensitive layer  40  of  FIG. 1  is exposed to patterned radiation either through the layers  60  and  50 , or through the first substrate  10  and pixel electrode layer  30 . However, if the incident radiation travels through the first substrate  10  and pixel electrode layer  30 , the radiation is obstructed by the integrated circuits  20 . Furthermore, in the embodiment of  FIG. 1 , the integrated circuits  20  are located in a layer between the first substrate  10  and the pixel electrodes  30 , and the pixel electrodes  30  are located between the radiation-sensitive layer  40  and the integrated circuits  20 . Thus, in this embodiment, it is necessary to form the pixel and common electrode layers  30 ,  50 , and radiation-sensitive layer  40  over the integrated circuits  20  on a side of the integrated circuits  20  opposite the active substrate  10 . Since the integrated circuits  20  can be relatively thick compared to the radiation-sensitive layer  40 , pixel electrode  30 , and common electrode  50 , forming continuous layers over the integrated circuits  20  can be difficult. Moreover, the mechanisms by which the integrated circuits  20  are located over the first substrate  10  can cause contamination, such as unwanted particles, in the various layers. 
     Therefore, in an alternative embodiment of the present invention illustrated in  FIG. 4 , the radiation-sensitive apparatus  5  has a radiation-sensitive layer  40  located between the integrated circuits  20  and the first substrate  10  and the pixel electrodes  30  are located between the radiation-sensitive layer  40  and the integrated circuits  20 . As shown in  FIG. 4 , the common electrode layer  50  is formed on the active side  11  of the first substrate  10 . The radiation-sensitive layer  40  is formed over the common electrode layer  50  and the patterned pixel electrodes  30  formed over the radiation-sensitive layer  40  and electrically separated by insulators  15  to define pixels  70 . Integrated circuits  20  are located over the pixel electrodes  30 , in this case with the pixel and control connection pads  22 , (and  28 , not shown) facing the first substrate  10  and the pixel electrodes  30 . The pixel and control connection pads  22 ,  28  are electrically connected to the pixel electrodes  30  and electrical connectors  32  (not shown in  FIG. 4 ). Suitable materials for enabling the electrical connection between the pixel and control connection pads  22 , (and  28 , not shown) and the pixel electrodes  30  and electrical connectors  32  (not shown) include solder balls and anisotropic conducting materials. Such materials and their application and curing are known in the printed circuit board industry. An encapsulating and insulating layer  14  can be formed (e.g. by coating) over the integrated circuits  20  and a protective layer  60  coated over the entire device. 
     This structure has the advantages of locating the integrated circuits  20  over the layers (e.g.  30 ,  40 ,  50 ) so that the layers are more planar. Furthermore, by positioning the integrated circuits  20  with the connection pads  22  (and  28 , not shown) facing towards the first substrate  10 , photolithographic steps are avoided since the connection pads  22  (and  28 , not shown) are directly connected to the electrical connections  32  (not shown), pixel connection wires  34  (not shown), or pixel electrodes  30 . As noted above with respect to  FIG. 1 , radiation  8  is incident upon the radiation-sensitive layer  40  either through the first substrate  10  or the protective layer  60 , but in the latter case is obstructed by the integrated circuits  20 . 
     In yet another radiation-sensitive apparatus  5  example, illustrated in  FIG. 5 , the integrated circuits  20  and the pixel electrodes  30  defining pixels  70  are formed in a common layer over the first substrate  10  active side  11 , for example on the radiation-sensitive layer  40 . The pixel electrodes  30  are insulated from each other by insulators  15  and covered with an encapsulating and insulating layer  14  and protective layer  60 . A common electrode  50  is formed on the first substrate  10 . This structure can be irradiated with radiation  8  from either the protective layer  60  side or the first substrate side  10 , but requires pixel connection wires  34  to electrically connect the pixel connection pads  22  to the pixel electrodes  30  (and the control connection pads  28  to the electrical connectors  32 , not shown in  FIG. 5 ). 
     In both the embodiments of  FIGS. 4 and 5 , an additional adhesive layer ( 12  in  FIG. 1 , not shown in  FIGS. 4 and 5 ) is used to adhere layers to the first substrate  10 , if needed. Alternatively, the first substrate  10  is treated (e.g. by chemical processes or by additional coated layers) to improve the adhesion of subsequently deposited layers such as the common electrode  50 , the radiation-sensitive layer  40 , or the pixel electrode layer  30 . 
     Referring to  FIGS. 6 and 7 , in an additional embodiment of the present invention, shielding layers  90  ( FIG. 6 ) or elements  90 A ( FIG. 7 ) are provided to prevent irradiation of layers or portions of layers in the radiation-sensitive apparatus  5 . Referring to  FIG. 6 , a layer  90  of a radiation-absorbing or opaque material, such as a metal is deposited over the radiation-sensitive layer  40  so that radiation incident on the radiation-sensitive layer  40  from the integrated circuit  20  and pixel connection pad  22  side of the apparatus  5  is greatly reduced. The first substrate  10  active side  11  has a common electrode  50 , a radiation-sensitive layer  40  and pixel electrodes  30  defining pixels  70  separated by insulators  15  formed thereon. A shielding layer  90  separates the pixel electrodes  30  from the integrated circuits  20 , except for pixel connection wires  34  conducting electrical signals through vias in the shielding layer  90 . Electrical connectors  32  (not shown) connected to control connection pads  28  (not shown) can be formed over the encapsulation and insulating layer  14 , and a protective layer  60  formed over the encapsulation and insulating layer  14 . Known photo-lithographic processes can be used to form the various layers and structures using known materials described above. In  FIG. 7 , the shielding layer is reduced to shielding elements  90 A protecting the integrated circuits  20  from incident radiation  8  passing through the first substrate  10 . The shielding elements  90 A are formed in a layer but the layer is not continuous and includes openings between the shielding elements  90 A. 
     While the shielding layer  90  and shielding elements  90 A are shown in  FIGS. 6 and 7  between the pixel electrode layer  30  and the encapsulating and insulating layer  14 , in other embodiments (not shown), shielding layers  90  can instead, or in addition, be located over or under the protective layer  60  or on either side of the first substrate  10  to control incident radiation exposure of the various layers. For example, the incidence of ambient light onto semiconductor materials can be deleterious to the electrical signals, since spurious electrical charges can be generated that increase noise in the electrical signals.  FIG. 6  locates the pixel electrodes  30  between the integrated circuits  20  and the radiation-sensitive layer  40  while  FIG. 7  locates the pixel electrodes  30  between the integrated circuits  20  in a common layer. 
     In various embodiments of the present invention, the integrated circuits  20  and the electrical signals are controlled in a variety of different ways. In the embodiments illustrated in  FIGS. 1 and 3 , for example, each pixel electrode  30  is independently electrically connected to a different pixel connection pad  22  on an integrated circuit  20  through a pixel connection wire  34 . Each pixel electrode  30  is electrically insulated from other pixel electrodes  30  and produces a separate electrical signal that is connected to an electronic circuit  26  ( FIG. 2 ) in the integrated circuit  20 . Each pixel electrode  30  is connected to a separate, identical electronic circuit  26  (not shown) that is then connected to a communications circuit for transmission to a electrical control circuit  80  through electrical connection wires  32 . In this embodiment, each pixel electrode  30  has its own electronic circuit. Such active-matrix control circuits are known in the art. 
     In an alternative embodiment illustrated in  FIGS. 8 and 9 , groups  72  of pixels are controlled together and share electrodes. The pixels are defined by the overlap of pixel electrodes  36  extending in a first direction and common electrodes  38  extending in a second direction different from the first direction formed on a side of the radiation-sensitive layer  40  (not shown) opposite the pixel electrodes  36 . Pixel electrodes  36  correspond to row electrodes and common electrodes  38  correspond to column electrodes. Each common electrode  38  is connected to a different connection pad  22  and each pixel electrode  36  is connected to a different connection pad  22 . Each common electrode  38  defines a plurality of pixels in combination with a corresponding plurality of pixel electrodes  36 . Likewise, each pixel electrode  36  defines a plurality of pixels in combination with a corresponding plurality of common electrodes  38 , forming an array of pixels. The electronic circuits  26  (not shown) control the common electrodes  38  and pixel electrodes  36  to provide an electrical bias across each pixel and the electronic circuits  26  (not shown) receive the electrical signals from the common electrodes  38  and the pixel electrodes  36 . Electronic circuits  26  (not shown) that provide such passive-matrix control circuits are known in the art. Integrated circuits  20 A can include the electronic circuits  26  (not shown) connected to the common electrodes  38  and integrated circuits  20 B can include the electronic circuits  26  connected to the pixel electrodes  36 . Alternatively, the electronic circuits  26  controlling the pixels in a group  72  can be formed in a single integrated circuit  20  (not shown) or are divided between different portions of different integrated circuits  20  (not shown). 
     In a further embodiment of the present invention, control connection pads  28  in integrated circuits  20 A located in a row over the first substrate  10  are connected through row control connectors  32 A (e.g. electrical wires) to the electronic control circuit  80 . Control connection pads  28  in integrated circuits  20 B located in a column over the first substrate  10  are connected through column control connectors  32 B (e.g. electrical wires) to the electronic control circuit  80 . Electronic control circuit  80  can provide passive-matrix control using circuits and methods well-known in the art. The use of the terms “row” and “column” herein are arbitrary and intended to denote structures formed in different directions (e.g. first and second directions).  FIG. 9  illustrates a larger passive-matrix-controlled structure corresponding to  FIG. 8 . The number of pixels within a group  72  of pixels in each dimension is constrained by the number of pixel connection pads  22  on an integrated circuit  20 . The larger the integrated circuits  20 , the more pixel connection pads  22  can be formed in the integrated circuits  20  and the larger the array of pixels formed in the group  72 . Multiple row or column integrated circuits  20 A or  20 B can control a single group  72  of pixels. 
     The first substrate  10  is rigid (for example made of relatively thick glass, metal or ceramic) or flexible (for example made of relatively thin glass, plastic, or metal foil). If the first substrate  10  is flexible, it is useful to have similarly flexible layers in the other layers of the various embodiments of the present invention to provide a flexible radiations-sensitive apparatus  5 . Referring to  FIG. 10 , in a further embodiment of the present invention, the radiation-sensitive layer  40  is segmented into spatially separate portions by insulators  15 A. The insulators  15 A can have different mechanical attributes, for example greater flexibility or a reduced likelihood of cracking under stress so that if the radiation-sensitive layer  40  is stressed by bending the first substrate  10 , the stress is applied to the insulators  15 A to a greater degree than to the radiation-sensitive layer  40  materials, reducing the likelihood of cracking the radiation-sensitive layer  40  materials. Similarly, the pixel electrodes  30  are separated with such an insulator  15 A as can the common electrode  50  to reduce stress in the materials forming the layers. However, as shown in  FIG. 13A  in a one-dimensional case and  13 B in a two-dimensional case, the common electrode  50  is electrically common so that each of the spatially separate portions are actually connected, for example at the edges or with small vias between portions. In another embodiment of the present invention, the connecting portions of the common electrode  50  can include different materials that are more stress resistant than the other portions of the common electrode  50 , thus reducing the likelihood of cracking. 
     In an embodiment, the separate portions are formed between the integrated circuits  20 , so that the stress is located preferentially between the integrated circuits  20 . Alternatively, separate portions are formed in alignment with the integrated circuits  20 , so that the stress is located preferentially in the integrated circuits  20 . Thin layers of crystalline semiconductor material, e.g. silicon, can bend and it can also bend the layers in the spatial location of the integrated circuit  20  than elsewhere in the layer structure. For example, it is known that metal oxides used as electrodes are prone to cracking under stress, and it is preferred to reduce the stress in the locations of the electrodes. 
     In either the embodiment of  FIG. 3  or the embodiment of  FIGS. 8 and 9 , the pixels can form a two-dimensional array capable of representing the patterns formed by incident patterned radiation, for example from a diagnostic x-ray or other radiation. Depending on the materials employed in the radiation-sensitive layer  40 , the electrical signal is a current or a charge. 
     The present invention can be used to provide medically diagnostic information. According to a method of the present invention illustrated in  FIG. 14 , electrical power is provided to the integrated circuits  20  and electronic control circuit  80  in step  200 . A radiation source is provided and the object (e.g. a patient) is located with respect to the radiation source so that the radiation passes through the object forming patterned radiation  8  (e.g. by differentially absorbing the radiation) that impinges on the radiation-sensitive layer  40  to expose the radiation-sensitive layer  40  to the patterned radiation  8  in step  205 , forming electrical signals in the radiation-sensitive layer  40 . The electronic circuits  26  control and receive the electrical signals which are then communicated to the electronic control circuit  80  in step  210 . The electrical signals are processed to form an image representative of the patterned radiation in step  215 . The processing can be done in the electronic control circuit  80  or in an image processor, such as a computer, as is known in the image processing arts. The resulting image can then be displayed, for example, on a large, flat-panel display, viewed by a diagnostician such as a radiologist, and a diagnosis made from the image. 
     Referring to  FIG. 11  and  FIG. 4 , a method of making a radiation-sensitive apparatus, includes providing a first substrate  10  having an active side  11  in step  100 . An optional adhesive layer or treatment is provided on the active side and a common electrode  50  is formed on the active side  11  in step  105 . A radiation-sensitive layer  40  is formed over the active side  11  of the first substrate  10  in step  110 , and is formed on the common electrode  50 . A plurality of pixel electrodes  30  is formed over the active side  11  of the first substrate  10 , for example on the radiation-sensitive layer  40 , in step  115 . The common electrode  50 , radiation-sensitive layer  40 , and pixel electrodes  30  are formed, for example, by evaporative deposition, sputtering, or coating sequential layers of materials. 
     The pixel electrodes  30  can be patterned using known photo-lithographic methods. 
     A plurality of spatially separated integrated circuits is provided (step  101 ) and located on the active side in step  120 . The integrated circuits  20  are made using integrated circuit fabrication processes known in the integrated circuit art. Each integrated circuit  20  includes a second individual substrate different and separate from the first substrate  10 , one or more electronic circuit(s) formed in or on the second substrate, and one or more pixel electrode connection pads  22  formed in or on the second substrate, each pixel electrode connection pad  22  electrically connected to at least one of the electronic circuit(s). The pixel electrodes  30  are separate from the integrated circuits  20  and each pixel electrode  30  is electrically connected to a pixel electrode connection pad  22 , for example by using metal deposition and patterning methods known in the photo-lithographic arts to form pixel connection wires  34  in step  125 . An electronic control circuit  80  is provided (step  140 ) and electrically connected to each electronic circuit  26  in each integrated circuit  20 , for example by forming electrical connectors  32  (e.g. metal wires) electrically connecting the control connection pads  28  (not shown in  FIG. 4 ) and the electronic control circuit  80  ( FIG. 3 , step  125 ). 
     Referring also to  FIG. 12 , the integrated circuits  20  are provided (step  101 ) in a process separate from that to the radiation-sensitive apparatus  5  by using methods known in the integrated circuit fabrication arts. For example, as shown in  FIG. 12 , a semiconductor substrate, e.g. a crystalline silicon substrate, are provided in step  102 , photo-lithographic processes employed to form electronic circuits in step  103 , and connection pads,  22 ,  28  for example made of patterned metal or silicon, formed on the integrated circuit in step  104 . Other connection structures known in the art (for example metal extrusions) compatible with electrical interconnections used in the structure of the present invention can be used. 
     The integrated circuits  20  are located using various methods known in the art, for example by picking and placing pre-made integrated circuits from a source substrate using adhesive or vacuum methods. The electrical connections from the connection pads (e.g.  22 ,  28 ) on the integrated circuit  20  can be made by depositing and patterning metal directly on the connection pads ( 22 ,  28 ) and connecting wires (e.g.  32 ,  34 ) using photo-lithography or through solder reflow methods or with anisotropic conductive materials. 
     An encapsulation and insulating layer  14  is formed over the integrated circuits  20  in step  130  of  FIG. 11 . The encapsulation and insulating layer  14  can be patterned if needed using conventional photo-lithographic processes to enable electrical connections between the connection pads ( 22 ,  28 ) and pixel connection wires  34 , electrical connections  32 , or pixel electrodes  30 . A protective layer  60  formed in step  135  can provide environmental robustness.  FIGS. 1 and 5  illustrate alternative embodiments of the present invention. In these cases, the order of layer deposition and patterning is different. For example, in the example of  FIG. 1 , the integrated circuits  20  are located (step  120 ) and patterned structures (e.g. vias) provided before the pixel electrodes  30  are formed (step  115 ), followed by the radiation-sensitive layer  40  (step  110 ) and common electrode  50  (step  105 ). In the example of  FIG. 5 , the steps of  FIG. 4  are replicated except that the encapsulating and insulating layer  14  is patterned differently to provide electrical connections between the connection pads ( 22 ,  28 ), the pixel electrodes  30 , and the electrical control circuit  80  (not shown). Pixel electrodes  30  and integrated circuits  20  can be located in a common layer in a structure similar to that of  FIG. 1 , as well as the illustrated structure of  FIG. 5  that is similar to  FIG. 4 . 
     A protective layer  60  can also be formed over the various layers in step  135  to protect the device. 
     In an embodiment, the electronic control circuit  80  is an integrated circuit mounted on the first substrate  10  or mounted externally to the first substrate  10  and electrically connected through an electrical connector  32 , using methods well-known in the printed-circuit-board arts. The electronic circuits  26  are responsive to electrical signals formed by the interaction of electromagnetic radiation and the radiation-sensitive layer  40 . The electrical signals are conducted by the pixel electrodes  30  through the pixel connection wires  34  (if present) and the pixel connection pads  22  to the electronic circuits  26 . The electronic circuits  26  then transmit the electrical signals through the control connection pads  28  (not shown) and electrical connectors  32  to the electronic control circuit  80 . 
     In various other methods of the present invention, a single common electrode co-extensive with the pixel electrodes  30  is formed on or over the active side  11  of the first substrate  10 . Pixel electrodes  30  and the integrated circuits  20  are formed in a common layer. 
     The integrated circuits  20  are located in a layer between the first substrate  10  and the pixel electrodes  30 , and the pixel electrodes  30  are located between the radiation-sensitive layer  40  and the integrated circuits  20 . In this method, a single common electrode  38 ,  50  is located co-extensive with the pixel electrodes  30  over the radiation-sensitive layer  40 . Alternatively, the pixel electrodes  30  and the integrated circuits  20  are located in a common layer. 
     In yet another alternative method, the radiation-sensitive layer  40  is located between the integrated circuits  20  and the first substrate  10  and the pixel electrodes  30  are located between the radiation-sensitive layer  40  and the integrated circuits  20 . In this structure, the single common electrode  38 ,  50  is located co-extensive with the pixel electrodes  30  between the radiation-sensitive layer  40  and the first substrate  10 . 
     In another method, a shielding layer  90  is located between the radiation-sensitive layer  40  and the integrated circuit  20  layer or shielding elements  90 A are formed between each integrated circuit  20  and the radiation-sensitive layer  40 . 
     In one method of forming control circuits for the radiation-sensitive apparatus  5 , each pixel electrode  30  is independently electrically connected to a single connection pad  22 ,  28 . 
     In another method of controlling radiation-sensitive apparatus  5 , an array of pixel electrodes  30  is formed extending in a first direction on a side of the radiation-sensitive layer  40  opposite the common electrodes  38 ,  50 . The pixel electrodes  30  are formed to extend in a second direction different from the first direction and overlap with the common electrodes  38 ,  50  to define pixels  70 . Each common electrode  38 ,  50  and each pixel electrode  30  is connected to a different connection pad  22 ,  28 . The electronic control circuits  80  are formed to control the common electrodes  38 ,  50  and pixel electrodes  30  to provide an electrical bias in each pixel  70  and the electronic control circuits  80  are formed to receive the electrical signals from the common electrodes  38 ,  50  and the pixel electrodes  30 . 
     In further methods of the present invention, arrays of pixel electrodes  30  and common electrodes  38 ,  50  are provided to define pixel groups  72  and each group is controlled by a different one or more integrated circuits  20 . The integrated circuits  20  are electrically connected to provide electrical signal communication from the integrated circuits  20  to a controller. In another embodiment, the integrated circuits  20  are formed into groups that are serially connected to the electronic control circuit  80 . The integrated circuits  20  can correspond to row and column control elements that are electrically connected with row and column control electrodes to the electronic control circuit  80 . 
     In another method, the radiation-sensitive layer  40 , the common electrode  38 ,  50 , or the pixel electrode  30  layer is segmented into spatially separate portions. The separations are made between the integrated circuits  20  or are made in locations that are directly above or below the integrated circuits  20 . 
     In other methods, the pixel electrodes  30  are formed in a two-dimensional array and provide electrical signals that are current or charge signals. In one method, the electronic circuits are provided in a crystalline semiconductor integrated circuit. 
     In another embodiment, a method of using a radiation-sensitive apparatus  5  made as described above includes providing electrical power to the integrated circuits  20  and electronic control circuit  80  exposing the radiation-sensitive layer  40  to patterned radiation, using the electronic control circuit  80  to receive the electrical signals from the integrated circuit  20 , and processing the electrical signals to form an image representative of the patterned radiation. 
     The present invention provides advantages over methods and structures known in the prior art. By providing circuits made independently of the first substrate, crystalline semiconductors having higher performance (improved speed and lower noise) than organic or thin-film circuits can be used to improve the sensitivity and quality of the acquired image signals. Furthermore, processing conditions and substrate material requirements are less stringent, leading to lower cost and higher yields in materials and processing. Processing resolutions are reduced since the first substrate and layers can be made in processes that have a lower resolution than those employed in making electronic devices in an integrated circuit. Larger substrates can be used at a lower cost, increasing the size of the acquired images and improving their diagnostic capability and usefulness. Because the integrated circuits are inorganic and can be packaged or encapsulated, the processing conditions used to form the various layers of the apparatus can be more rigorous (e.g. higher heat, more potent chemicals). Flexible substrates are more readily employed. 
     The present invention can be employed in radiographic systems. In particular, the present invention can be practiced with x-ray diagnostic equipment. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it should be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     PARTS LIST 
     
         
         D distance 
           5  radiation-sensitive apparatus 
           8  radiation 
           10  first substrate 
           11  active side 
           12  adhesive layer 
           14  encapsulating and insulating layer 
           15 ,  15 A insulator 
           20  integrated circuit 
           20 A integrated circuit 
           20 B integrated circuit 
           22  pixel connection pad 
           24  second substrate 
           26  electronic circuits 
           28  control connection pad 
           30  pixel electrode 
           32  electrical connector 
           32 A row control connector 
           32 B column control connector 
           34  pixel connection wire 
           36  pixel electrode 
           38  common electrode 
           40  radiation-sensitive layer 
           50  common electrode 
           60  protective layer 
           70  pixel 
           72  pixel group 
           80  electronic control circuit 
           90  shielding layer 
           90 A element 
           100  provide first substrate step 
           101  provide integrated circuits step 
           102  provide crystalline substrate step 
           103  form electronic circuits step 
           104  form connection pads step 
           105  form common electrode step 
           110  form radiation-sensitive layer step 
           115  form pixel electrodes step 
           120  locate integrated circuits step 
           125  form electrical connections step 
           130  form insulating and encapsulating layer step 
           135  form protective layer step 
           140  provide electronic circuit control step 
           200  provide electrical power step 
           205  expose radiation-sensitive layer step 
           210  control and receive electrical signals step 
           215  process electrical signals to form image step