Photoelectric conversion device, manufacturing method thereof, and x-ray imaging system including the device

In order to provide a photoelectric conversion device of high S/N ratio or high resolution in which the outputs of sensor cells except any defective sensor cell can be made to have normal values, thereby to obtain data of higher precision, any switching element that does not operate normally is removed in a photoelectric conversion device wherein a plurality of sensor cells, in each of which a photoelectric element and a switching element are connected, are arrayed in two dimensions on a substrate.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a photoelectric conversion device, a
 method of manufacturing the device, and an X-ray imaging system including
 the device. More particularly, it relates to a photoelectric conversion
 device wherein a plurality of sensor cells, in each of which a
 photoelectric element and a switching element are connected, are arrayed
 in two dimensions on a substrate, a method of manufacturing the device,
 and an X-ray imaging system including the device.
 Also, the present invention is well suited for applications to a
 photoelectric conversion device which has photoelectric elements arrayed
 in two dimensions for actual-size reading in, for example, a facsimile
 equipment, a digital copier or an X-ray imaging apparatus, and to a method
 of repairing the photoelectric conversion device.
 Further, the present invention pertains to an X-ray imaging system in which
 the above photoelectric conversion device having the photoelectric
 elements of two-dimensional arrayal is assembled.
 2. Related Background Art
 Heretofore, a reading system which is configured of a scaling-down optical
 system and a CCD (charge-coupled device) type sensor has been employed as
 the reading system of a facsimile equipment, a digital copier, an X-ray
 imaging apparatus or the like. In recent years, however, photoelectric
 semiconductor materials typified by hydrogenated amorphous silicon
 (hereinbelow, expressed as "a-Si") have been being developed. This has
 resulted in the remarkable developments of so-called "close contact type
 sensors" in each of which photoelectric elements and a signal processing
 portion are formed on a substrate of large area so as to adopt an optical
 system for the actual-size reading of an information source.
 In particular, the a-Si is usable, not only as the photoelectric material,
 but also as the material of thin-film field effect transistors
 (hereinbelow, simply expressed as "transistors"). Accordingly, it has the
 advantage that a semiconductor layer for photoelectric conversion and a
 semiconductor layer for the transistors can be formed at the same time.
 An example of a photoelectric conversion device utilizing such a-Si is
 disclosed in the official gazette of Japanese Patent Application Laid-open
 No. 8-116044. It will now be explained with reference to FIG. 1 and FIGS.
 2A and 2B of the accompanying drawings. FIG. 1 is a circuit diagram
 showing the whole circuit of the photoelectric conversion device. Besides,
 FIG. 2A is a schematic plan view of constituent elements which correspond
 to one sensor cell of the photoelectric conversion device. Further, FIG.
 2B is a schematic sectional view taken along line 2B--2B indicated in FIG.
 2A.
 First, the construction of the photoelectric conversion device will be
 explained. Referring to FIG. 1, each sensor cell is configured of a
 photoelectric element S, a capacitor C and a transistor T. In the
 photoelectric conversion device, the sensor cells totaling nine
 (3.times.3) are divided into three blocks of respective columns. That is,
 one block consists of three sensor cells.
 In the figure, symbols S11 to S33 denote the photoelectric elements S. The
 lower electrode side of each photoelectric element S is indicated by
 letter G, while the upper electrode side thereof is indicated by letter D.
 In addition, symbols C11 to C33 denote the capacitors for storage, and
 symbols T11 to T33 the transistors for transferring data.
 Besides, symbol Vs designates a power source (or supply voltage) for
 reading out a converted charge signal, and symbol Vg a power source (or
 supply voltage) for refreshment. These power sources Vs and Vg are
 respectively connected to the G electrodes of all the photoelectric
 elements S11 to S33 through a switch SWs and a switch SWg. The switch SWs
 is connected to a refreshment control circuit RF through an inverter,
 while the switch SWg is connected thereto directly. The switch SWg is
 controlled so as to turn "ON" during a refreshing time period.
 Further, a part enclosed with a broken line in FIG. 1 is formed on an
 identical insulated substrate of large area. In the enclosed part, the
 sensor cell having the photoelectric element S11 is illustrated as the
 plan view in FIG. 2A. Also, a plane along the dot-and-dash line 2B--2B
 indicated in FIG. 2A is illustrated as the sectional view in FIG. 2B.
 Referring to FIG. 2B, the sensor cell generally shown in FIG. 2A includes a
 lower electrode 1 which forms a gate electrode on the insulating
 substrate, a gate insulator film 2, an i-layer 3 which is a semiconductor
 layer effecting photoelectric conversion, an n-layer 4 which hinders the
 injection of holes, and an upper electrode layer 5 which forms source and
 drain electrodes. This sensor cell is fabricated in such a way that the
 lower electrode layer 1, the gate insulator film 2, the i-layer 3, the
 n-layer 4, and the upper electrode layer 5 serving as the source and drain
 electrodes are first stacked in the order mentioned, that the upper
 electrode layer 5 is subsequently etched to form the source and drain
 electrodes, and that the n-layer 4 is thereafter etched to form a channel
 portion.
 In the above photoelectric conversion device, the capacitor C11 and the
 photoelectric element S11 are disposed without special isolation. This is
 because the photoelectric element S11 and the capacitor C11 are configured
 of the same layers. Such a configuration is also the feature of the
 photoelectric conversion device. Besides, the capacitor C11 is formed
 while keeping the areas of the electrodes of the photoelectric element S11
 large. The reason therefor is that, when the areas of the electrodes of
 the photoelectric element S11 are enlarged, the sensitivity of the sensor
 is enhanced, leading to decrease in the quantity of exposure to X-rays as
 is required for the photoelectric conversion device of, for example, the
 X-ray imaging apparatus.
 In addition, a silicon nitride (SiN) film for passivation and a phosphor
 layer of cesium iodide (CsI) or the like are formed at the upper part of
 the sensor cell. When X-rays are caused to fall on the sensor cell, they
 are converted by the phosphor layer CsI into light or visible radiation
 (indicated by arrows of broken lines), which enters the photoelectric
 element S11.
 Next, an example of the operation of the photoelectric conversion device
 will be explained. Referring also to FIG. 1, the output of the charge
 signal converted in each photoelectric element S is stored in the storage
 capacitor C. The stored signal is fetched on a signal wiring line SIG when
 the transistor T is turned "ON" by an output signal from a shift register
 SR1. The fetched charge signal is inputted to a detecting integrated
 circuit IC when a switch M is turned "ON" by a control signal delivered
 from a shift register SR2.
 More concretely, electric signals outputted from the sensor cells of one
 block are simultaneously fetched on one signal wiring line SIG, and they
 are collectively transferred to the detecting integrated circuit IC by the
 shift register SR2. Each of the electric signals transferred to the
 detecting integrated circuit IC is amplified into an output voltage Vout
 by an amplifier Amp.
 The operation of the photoelectric conversion device will now be detailed
 with reference to a timing chart illustrated in FIG. 3. First of all, a
 high level voltage Hi is applied to control wiring lines g1 to g3 and s1
 to s3 by the shift registers SR1 and SR2, respectively. Then, the
 transistors T11 to T33 and the switches M1 to M3 are turned "ON" owing to
 the high level outputs Hi of the shift register SR2. Thus, the electrodes
 D of all the photoelectric elements S11 to S33 become a ground (GND)
 potential. This is because the input terminal of the integrating detector
 Amp is designed so as to have the GND potential.
 A high level voltage Hi is outputted from the refreshment control circuit
 RF, thereby to turn "ON" the switch SWg. Thus, the electrodes G of all the
 photoelectric elements S11 to S33 are brought to a plus potential by the
 refreshing supply voltage Vg. Then, all the photoelectric elements S11 to
 S33 fall into a refreshment mode and are refreshed.
 Subsequently, a low level voltage Lo is outputted from the refreshment
 control circuit RF, thereby to turn "ON" the switch SWs. Thus, the
 electrodes G of all the photoelectric elements S11 to S33 are brought to a
 minus potential by the reading supply voltage Vs. Then, all the
 photoelectric elements S11 to S33 fall into a photoelectric conversion
 mode, and the capacitors C11 to C33 are simultaneously initialized.
 Under this state, a low level voltage Lo is applied to the control wiring
 lines g1 to g3 and s1 to s3 by the shift registers SR1 and SR2,
 respectively. Then, the switches M1 to M3 for the transistors T11 to T33
 are turned "OFF". Besides, the electrodes D of all the photoelectric
 elements S11 to S33 become open DC (direct current)-wise, but their
 potentials are held by the corresponding capacitors C11 to C33.
 Since, however, the X-rays are not caused to fall on the sensor at this
 point of time, the light does not enter any of the photoelectric elements
 S11 to S33. In consequence, a photocurrent does not flow through any of
 the photoelectric elements S11 to S33. Thereafter, when the X-rays are
 caused to emerge in pulse-like fashion, to pass through a subject such as
 human body and to fall on the phosphor layer CsI, they are converted into
 the light, which enters the individual photoelectric elements S11 to S33.
 The light contains information on the internal structure of the subject
 such as human body. The photocurrents based on the light are stored in the
 individual capacitors C11 to C33 as electric charges, which are retained
 even after the end of the fall of the X-rays on the sensor.
 Subsequently, a control pulse of high level (high level voltage Hi) is
 impressed on the control wiring line g1 by the shift register SR1.
 Besides, control pulses of high level (high level voltage Hi) are
 successively impressed on the control wiring lines s1 to s3 by the shift
 register SR2. Thus, output voltages v1 to v3 each being the voltage Vout
 are successively delivered through the switches M1 to M3. Likewise, the
 remaining light signals (or photocurrents) are successively delivered by
 the control signals of high level or low level (high level voltage Hi or
 low level voltage Lo) produced from the shift registers SR1 and SR2. In
 this way, the two-dimensional information items on the internal structure
 of the human body or the like are derived as output voltages v1 to v9.
 Incidentally, a static image can be obtained by the operation stated above.
 On the other hand, a dynamic image can be obtained by repeating such
 operations.
 In the photoelectric conversion device exemplified here, the electrodes G
 of the photoelectric elements S are connected in common to a horizontal
 output line. Besides, the horizontal output line is controlled to the
 potentials of the refreshing power source Vg and reading power source Vs
 through the respective switches SWg and SWs. Therefore, all the
 photoelectric elements S11 to S33 can be simultaneously changed over
 between the refreshment mode and the photoelectric conversion mode.
 Accordingly, the optical output can be derived by one transistor T per
 sensor cell without executing any complicated control.
 The photoelectric conversion device has been explained above in relation to
 the case of transferring and outputting the signals with the construction
 wherein the nine sensor cells are arranged into the (3.times.3)
 two-dimensional arrayal, and wherein one block is constituted by the three
 sensor cells. However, the aspect of performance of the photoelectric
 conversion device is not restricted to the foregoing construction, but by
 way of example, (5.times.5) sensor cells numbering five per mm in each of
 the vertical and horizontal directions of the device may well be arranged
 in two dimensions into an arrayal of (2000.times.2000) sensor cells. Thus,
 it is possible to fabricate an X-ray detector whose size is 40 cm.times.40
 cm. When an X-ray imaging apparatus or the like is constructed by
 combining the X-ray detector with an X-ray generator instead of an X-ray
 film, it can be used for a roentgenological chest examination etc.
 The roentgenological chest examination with the X-ray imaging apparatus is
 capable of instantly projecting its result on a CRT (cathode-ray tube),
 unlike such an examination using the X-ray film. Further, it is capable of
 converting the result of detection into an output meeting a special
 purpose, through the digitization of the detected result and the image
 processing of digital data with a computer by way of example.
 Besides, the converted outputs can be saved or retained in a magneto-optic
 disk. Accordingly, an image in the past can be instantly searched for and
 outputted. Moreover, the sensitivity of the X-ray imaging apparatus is
 higher than that of the X-ray film, and a clear image can be obtained with
 feeble X-rays of less influence on the human body.
 Meanwhile, in manufacturing the photoelectric conversion device as stated
 above, some of the sensor cells fail to normally function in not a few
 cases. By way of example, when an amorphous silicon layer is to be
 deposited on a substrate, dust etc. sometimes come to lie on the
 substrate, but it is difficult to completely eliminate such dust etc. More
 concretely, when minute motes having appeared during the manufacture,
 trash having fallen off from the wall of a thin-film depositing equipment,
 etc. come to lie on the substrate, the complete elimination thereof is
 difficult. Accordingly, wiring lines laid on an identical plane or wiring
 lines laid at different levels might short-circuit.
 Next, the outputs of abnormal sensor cells ascribable to the practicable
 short-circuits of the wiring lines of the elements will be explained in
 conjunction with FIGS. 4 and 5. FIG. 4 illustrates a case where the
 transistor T11 is in the state in which the source electrode and drain
 electrode thereof have short-circuited. The state results from a situation
 where resist patterns for forming the source electrode and the drain
 electrode have been connected by minute trash or the like. FIG. 5 is a
 timing chart of the operation of the device in such a case.
 Usually, the output charges of the photoelectric element S11 are
 continually generated during the irradiation of the sensor with light.
 Besides, the charges are stored in the storage capacitor C11. However, in
 the illustrated case where the source electrode and the drain electrode
 have short-circuited, the photoelectric element S11 becomes as if it were
 connected with the signal wiring line SIG by turning "ON" the transistor
 T11. Consequently, the quantity of charges to be stored in the storage
 capacitor C11 becomes about 1/3 of an ordinary value. Accordingly, when
 the output of the photoelectric element S11 (indicated at v1 in FIG. 5) is
 fetched, it decreases to about 1/3 in comparison with the output of the
 usual operation as seen from FIG. 5.
 To the contrary, when the outputs of the photoelectric elements S21 and S31
 (respectively indicated at v4 and v7 in FIG. 5) are fetched, each of them
 has about 1/3 of the ordinary value added thereto. As a result, each of
 the outputs v4 and v7 increases to about 4/3 in comparison with the output
 of the usual operation as seen from FIG. 5.
 Next, there will be explained the operation of the device in the case where
 the source electrode and gate electrode of the transistor T22 have
 short-circuited as illustrated in FIG. 4. Minute trash or the like
 sometimes results in the short-circuit between the source electrode and
 the gate electrode, as in the foregoing case of the transistor T11.
 In such a case, the transistor T22 becomes as if the signal wiring line SIG
 and the control wiring line g2 were connected therethrough. Accordingly,
 the control wiring line g2 at the moment at which the outputs of the
 photoelectric element S12 and those S22 and S32 (respectively indicated at
 v2 and at v5 and v8 in FIG. 5) are fetched, is held at a potential (in
 general, 0 V to 5 V) in the case of turning "OFF" the transistors T.
 Consequently, each of the outputs of the photoelectric elements S12, S22
 and S32 (respective outputs v2, v5 and v8) decreases to a much smaller
 value in comparison with the output of the usual operation as seen from
 FIG. 5.
 In the presence of the defective sensor cells as stated above, the number
 of the erroneous outputs needs to be lessened as far as possible. It has
 therefore been common practice that the signal wiring lines SIG connected
 with the defective sensor cells are partially vaporized away to disconnect
 by laser irradiation.
 Such a countermeasure will be explained with reference to FIG. 6. This
 figure illustrates the state in which the signal wiring lines SIG
 connected with the defective sensor cell 11 (here, the "sensor cell 11"
 includes the elements S11, C11 and T11, and such terminology shall apply
 also to the ensuing explanation) and sensor cell 22 in FIG. 4 have been
 partially vaporized away to disconnect by the laser irradiation.
 Square parts of broken lines depicted between the signal wiring lines SIG
 and the respective transistors T11 and T22 of the sensor cells 11 and 22
 are those parts of the signal wiring lines SIG connected with the
 defective sensor cells which have been vaporized away to disconnect by the
 laser irradiation. Incidentally, the other parts of the sensor cells 11
 and 22 are the same as shown in FIG. 4 and shall be omitted from
 explanation.
 Here, a schematic plan view of the sensor cell 11 and the individual wiring
 lines is illustrated in FIG. 7A. Besides, a schematic sectional view taken
 along dot-and-dash line 7B--7B indicated in FIG. 7A is illustrated in FIG.
 7B. Further, examples of the operation of the photoelectric conversion
 device in the case where the defective sensor cells 11 and 22 have been
 subjected to the treatment or repair shown in FIGS. 7A and 7B, will be
 explained with reference to a timing chart illustrated in FIG. 8. By the
 way, in FIGS. 7A and 7B, the transistor T11 is illustrated in the state in
 which the source electrode and the drain electrode short-circuit. Besides,
 as in the foregoing, a square part of broken line in FIG. 7A is that part
 of the signal wiring line SIG which has been vaporized away to disconnect
 by the laser irradiation.
 FIG. 7B illustrates the sectional structure of a portion where the signal
 wiring line SIG has been disconnected. As seen from the figure, not only
 the part of the signal wiring line SIG, but also the passivating silicon
 nitride layer SiN overlying the signal wiring line SIG and the gate
 insulator film 2, i-layer 3 and n-layer 4 underlying the signal wiring
 line SIG have been partially vaporized away by the laser irradiation.
 Even when the signal wiring line SIG connected with the defective sensor
 cell 11 has been vaporized away to disconnect by the laser irradiation,
 the output v1 of the photoelectric element S11 does not demonstrate the
 value in the usual operation. The output v1 of the photoelectric element
 S11, however, is prevented from being superposed by leakage. Accordingly,
 the outputs v4 and v7 of the respective photoelectric elements S21 and S31
 become as shown in FIG. 8.
 Likewise, the signal wiring line SIG connected with the defective sensor
 cell 22 has been vaporized away to disconnect by the laser irradiation.
 Even when the signal wiring line SIG connected with the defective sensor
 cell 22 has been vaporized away to disconnect by the laser irradiation,
 the output v5 of the photoelectric element S22 does not demonstrate the
 value in the usual operation.
 However, the gate line signal of the transistor T22 of the sensor cell 22
 is prevented from being superposed by leakage, similarly to the effect in
 the case where the sensor cell 11 has been treated. Accordingly, the
 outputs v2 and v8 of the respective photoelectric elements S12 and S32
 become as shown in FIG. 8.
 Therefore, the outputs Vout shown in FIG. 5 change into those Vout shown in
 FIG. 8 in the above way that the signal wiring lines SIG connected with
 the defective sensor cells are vaporized away to disconnect by the laser
 irradiation. More specifically, the outputs Vout shown in FIG. 8 have been
 improved so as to be normal except the outputs v1 and v5 of the respective
 defective sensor cells 11 and 22.
 Nevertheless, diminishing the X-rays influential on the human body, even
 slightly, is required of the photoelectric conversion device which has the
 photoelectric elements arrayed in two dimensions for the actual-size
 reading in, for example, the X-ray imaging apparatus. It is also required
 to obtain data of higher precision.
 In order to meet the requirements, an expedient in which the area of each
 photoelectric element is enlarged has been generally adopted. Since,
 however, semiconductor patterns have been made highly dense, signal wiring
 lines connected with sensor cells have been reduced in size. It is
 accordingly difficult that, as stated above, the signal wiring lines
 connected with the defective sensor cells are partially vaporized away to
 disconnect by the laser irradiation.
 More specifically, in case of manufacturing the photoelectric conversion
 device of high S/N (signal-to-noise) ratio or high resolution, the signal
 wiring lines connected with the sensor cells are partially used for the
 photoelectric elements, and yet, they are reduced in size or removed.
 Therefore, it is sometimes impossible that the signal wiring lines
 connected with the defective sensor cells are partially vaporized away to
 disconnect by the laser irradiation. Accordingly, it is sometimes
 impossible that the outputs of the sensor cells except the defective ones
 are brought to the usual values.
 SUMMARY OF THE INVENTION
 In order to solve the above problem, the present invention has for its
 object to provide a photoelectric conversion device of high S/N ratio or
 high resolution in which the outputs of sensor cells except defective ones
 can be made normal values so as to obtain data of higher precision, a
 method of manufacturing the photoelectric conversion device, and an X-ray
 imaging system which includes the photoelectric conversion device.
 It is an object of the present invention to provide a photoelectric
 conversion device wherein a plurality of sensor cells, in each of which a
 photoelectric element and a switching element are connected, are arrayed
 in two dimensions on a substrate, the switching element of at least one of
 the sensor cells having been removed.
 It is another object of the present invention to provide a method of
 manufacturing a photoelectric conversion device wherein a plurality of
 sensor cells, in each of which a photoelectric element and a switching
 element are connected, are arrayed in two dimensions on a substrate,
 comprises the step of vaporizing away any of the switching elements that
 does not operate normally, by laser irradiation.
 It is still another object of the present invention to provide an X-ray
 imaging system, comprises a photoelectric conversion device which includes
 a phosphor for converting inputted X-rays into light; signal processing
 means for processing a signal delivered from said photoelectric conversion
 device; recording means for recording a signal delivered from said signal
 processing means; displaying means for displaying the signal delivered
 from said signal processing means; transmission processing means for
 transmitting said signal delivered from said signal processing means; and
 an X-ray source which generates the X-rays; said photoelectric conversion
 device including a plurality of sensor cells in each of which a
 photoelectric element and a switching element are connected, which are
 arrayed in two dimensions on a substrate, and in at least one of which the
 switching element has been removed.
 It is still another object of the present invention to provide a method of
 manufacturing a photoelectric conversion device wherein a plurality of
 sensor cells, each of which has a photoelectric element and a switching
 element, are arrayed on a substrate, comprises the step of selecting any
 defective cell from among the sensor cells, and thereafter removing the
 switching element of the defective cell.
 According to the present invention, the defective transistor (switching
 element) itself is removed by the laser beam irradiation or the like, so
 that a reliable treatment or repair can be carried out in spite of the
 smaller size of each sensor cell. Moreover, since the transistor itself is
 removed, a desired part can be electrically cut with a high reliability.
 Further, according to the present invention, an erroneous output ascribable
 to the defective cell can be prevented from affecting any other cell
 thereby to obtain a preciser output signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 EMBODIMENT 1
 Now, an embodiment of the present invention will be described in detail
 with reference to the drawings. FIG. 9 is a schematic circuit diagram
 showing the whole circuit of an example of a photoelectric conversion
 device in this embodiment. Referring to FIG. 9, each sensor cell is
 configured of a photoelectric element S, a capacitor C and a transistor
 (for example, a thin-film transistor) T. In the photoelectric conversion
 device, the sensor cells totaling nine (3.times.3) are divided into three
 blocks of respective columns. That is, one block consists of three sensor
 cells. In the figure, symbols S11 to S33 denote the photoelectric elements
 S. The lower electrode side of each photoelectric element S is indicated
 by letter G, while the upper electrode side thereof is indicated by letter
 D. In addition, symbols C11 to C33 denote the capacitors for storage, and
 symbols T11 to T33 the transistors for transferring data.
 Further, the photoelectric conversion device includes a shift register
 (SR1) 10 which turns "ON"/"OFF" the transistors T, control wiring lines 11
 by which control signals outputted from the shift register (SR1) 10 are
 delivered to the transistors T, signal wiring lines (SIG) 12 on which
 electric signals stored in the capacitors C are fetched, and a detecting
 integrated circuit (IC) 13 which has a shift register (SR2) 14 for
 fetching the electric signals and an amplifier (Amp) 15 for amplifying and
 delivering an output voltage Vout.
 Besides, symbol Vs designates a power source (or supply voltage) 16 for
 reading out a converted charge signal, and symbol Vg a power source (or
 supply voltage) 17 for refreshment. These power sources Vs and Vg are
 respectively connected to the G electrodes of all the photoelectric
 elements S11 to S33 through a switch (SWs) 19 and a switch (SWg) 20. The
 switch (SWs) 19 is connected to a refreshment control circuit (RF) 21
 through an inverter, while the switch (SWg) 20 is connected thereto
 directly.
 Incidentally, portions of the same functions as in FIGS. 1, 4 and 6
 referred to before have the same symbols assigned thereto and shall not be
 repeatedly explained.
 Next, the operation of the photoelectric conversion device in this
 embodiment will be described. The output of the electric signal converted
 in the photoelectric element S which is included in each sensor cell
 operating normally, is stored in the storage capacitor C. The stored
 signal is fetched on the signal wiring line (SIG) 12 when the transistor T
 is turned "ON" by the output signal from the shift register (SR1) 11. The
 fetched charges are inputted to the detecting integrated circuit (IC) 13
 when a switch M (any of M1 to M3) is turned "ON" by a control signal
 delivered from the shift register (SR2) 14.
 More concretely, the electric signals outputted from the sensor cells of
 one block are simultaneously fetched on one signal wiring line (SIG) 12,
 and they are collectively transferred to the detecting integrated circuit
 (IC) 13 by the shift register (SR2) 14. Each of the electric signals
 transferred to the detecting integrated circuit (IC) 13 is delivered as
 the output voltage Vout by the amplifier (Amp) 15.
 Meanwhile, the sensor cells which do not operate normally are treated or
 repaired as explained below. It is assumed here that the transistor T11 in
 the sensor cell 11 failing to operate normally has had its source
 electrode and drain electrode short-circuited as illustrated in FIG. 4
 referred to before. It is also assumed that the transistor T22 in the
 sensor cell 22 has had its source electrode and gate electrode
 short-circuited as in the foregoing. In the photoelectric conversion
 device shown in FIG. 9, square parts of broken lines existing at the
 positions of the respective transistors T11 and T22 of the sensor cells 11
 and 22 are pattern circuit parts which have been vaporized away and
 removed by laser irradiation as illustrated in FIG. 6.
 Next, the sensor cells not operating normally and the respective wiring
 lines will be explained in conjunction with FIGS. 10A to 10D. FIG. 10A is
 a schematic plan view of the sensor cell 11 and the wiring line SIG in the
 photoelectric conversion device of high S/N (signal-to-noise) ratio or
 high resolution. Besides, FIG. 10B is a schematic sectional view taken
 along dot-and-dash line 10B--10B indicated in FIG. 10A. Further, FIGS. 10C
 and 10D are a schematic plan view and a schematic sectional view showing
 the state in which the transistor T11 shown in FIGS. 10A and 10B has been
 vaporized away and removed as the element itself by the laser irradiation.
 Incidentally, portions of the same functions as in FIGS. 2A and 2B and 7A
 and 7B referred to before have the same symbols assigned thereto and shall
 be omitted from explanation. Also, the constituents of the photoelectric
 element S11 shown in FIGS. 10B and 10D are the same as in the foregoing
 and shall be omitted from explanation.
 The constructions of each sensor cell etc. in this embodiment differ from
 those of each sensor cell etc. explained before, as stated below. As
 understood by comparing FIG. 10A with FIG. 7A, the sensor cell 11 differs
 in pattern in that the length of the signal wiring line SIG is reduced to
 enlarge the area of the photoelectric element S11. This structure is
 intended to manufacture a photoelectric conversion device of higher
 sensitivity in order that the quantity of exposure to, for example, X-rays
 may be diminished.
 As understood by comparing FIG. 10C with FIG. 7A, the sensor cell 11
 differs in pattern in that, as in the comparison of FIG. 10A with FIG. 7A,
 the length of the signal wiring line SIG is reduced to enlarge the area of
 the photoelectric element S11. As a further difference, the signal wiring
 line SIG connected with the defective sensor cell 11 has been partially
 vaporized away to disconnect in the case of FIG. 7A, whereas the
 transistor T11 as the whole element has been vaporized away and removed in
 the case of FIG. 10C.
 More specifically, FIGS. 7A and 7B correspond to the situation where the
 signal wiring lines SIG connected with the defective sensor cells 11 and
 22 in FIG. 4 have been partially vaporized away to disconnect by the laser
 irradiation. In contrast, FIGS. 10C and 10D correspond to the situation
 where the transistors T included in the defective sensor cells 11 and 22
 assumed in this embodiment have been vaporized away to electrically
 disconnect by the laser irradiation.
 In this embodiment, the signal wiring lines SIG connected with the
 defective sensor cells cannot be vaporized away to disconnect by the laser
 irradiation, for the reason stated before. Therefore, the defective
 transistors T are vaporized away by the laser irradiation, thereby to
 disconnect the defective sensor cells from the signal wiring lines SIG.
 Thus, the outputs of the sensor cells except the defective ones can be
 made to have the normal values.
 That is, in the photoelectric conversion device shown in FIG. 9, the
 transistor T11 of the sensor cell 11 and the transistor T22 of the sensor
 cell 22 have been entirely vaporized away and removed by the laser
 irradiation, and these sensor cells and the signal wiring lines SIG have
 been disconnected. Concretely, the transistor T11 has been removed as best
 shown in FIG. 10D.
 FIG. 10D illustrates the sectional structure of a portion where the
 transistor T11 has been disconnected. As seen from the figure, not only
 the whole transistor T11, but also the passivating silicon nitride layer
 SiN, and the gate insulator film 2, i-layer 3 and n-layer 4 underlying the
 signal wiring line SIG have been partially vaporized away by the laser
 irradiation.
 Even when the transistor T11 connected with the sensor cell 11 failing to
 operate normally has been vaporized away to disconnect by the laser
 irradiation, the output v1 of the photoelectric element S11 does not
 demonstrate the value in the usual operation. The output v1 of the
 photoelectric element S11, however, is prevented from being superposed by
 leakage. Accordingly, the outputs v4 and v7 of the respective
 photoelectric elements S21 and S31 become as shown in FIG. 8.
 Likewise, the defective transistor T22 of the sensor cell 22 has been
 vaporized away to disconnect by the laser irradiation. Herein, the
 passivating silicon nitride layer SiN, and the gate insulator film 2,
 i-layer 3 and n-layer 4 underlying the signal wiring line SIG have been
 partially vaporized away by the laser irradiation. Even when the defective
 sensor cell 22 has been vaporized away to disconnect by the laser
 irradiation, the output v5 of the photoelectric element S22 does not
 demonstrate the value in the usual operation.
 However, the gate line signal of the transistor T22 of the sensor cell 22
 is prevented from being superposed by leakage, similarly to the effect in
 the case where the sensor cell 11 has been treated. Accordingly, the
 outputs v2 and v8 of the respective photoelectric elements S12 and S32
 become as shown in FIG. 8.
 Further, strictly speaking, unless the treatment is carried out, the
 amplitudes of the output signals of the sensor cells, except the outputs
 v1 and v5 of the respective photoelectric elements S11 and S22, become
 larger than the amplitudes of the output signals shown in FIG. 5. The
 reason therefor is that the photoelectric elements S of the photoelectric
 conversion device in this embodiment are larger in area than the
 photoelectric elements S of the photoelectric conversion device shown in
 FIG. 1.
 Next, examples of the packaging of a photoelectric conversion device having
 2000.times.2000 sensor cells will be explained in conjunction with FIGS.
 11 and 12. These figures are plan views each showing the packaging of the
 photoelectric conversion device having 2000.times.2000 sensor cells. In
 case of constructing the 2000.times.2000 detectors, the number of the
 constituent elements within a larger square of broken line indicated in
 FIG. 9 may be increased in both the vertical and horizontal directions of
 the figure. In this case, however, the control wiring lines g increase to
 2000 lines consisting of g1 to g2000. Also, the signal wiring lines SIG
 increase to 2000 lines consisting of sig1 to sig2000.
 Further, each of the shift register SR1 and detecting integrated circuit IC
 must control and process the 2000 lines and enlarges in scale. When it is
 fabricated as an element of one chip, the chip becomes very large, which
 is demeritorious in the points of available percentage in the fabrication,
 the price of the element, etc.
 Therefore, the shift register (SR1) 10 is so fabricated that every 100
 stages, for example, are formed on one chip, thereby to construct twenty
 shift registers (SR1-1 to SR1-20). Also, the detecting integrated circuit
 (IC) 13 is so fabricated that every 100 processing circuits are formed on
 one chip, thereby to construct twenty detecting integrated circuits (IC1
 to IC20).
 In the example of FIG. 11, twenty chips (SR1-1 to SR1-20) are packaged on
 the left side (L) of the photoelectric conversion device, and twenty chips
 (IC1 to IC20) on the lower side (D). The control wiring lines g and signal
 wiring lines SIG in the numbers of 100 per chip are connected with the
 corresponding chips by wire bonding. In FIG. 11, a square part of broken
 line corresponds to the larger square indicated by the broken line in FIG.
 9. By the way, the outward connections of the chips totaling forty are
 omitted from illustration. Also, the constituent elements of the device,
 such as SWg, SWs, Vg, Vs and RF, are omitted from illustration.
 Twenty outputs (Vout) are derived from the detecting integrated circuits
 IC1 to IC20. They may be serialized through switches etc., or may well be
 directly delivered so as to be processed in parallel.
 On the other hand, in the example of FIG. 12, ten chips (SR1-1 to SR1-10)
 are packaged on the left side (L) of the photoelectric conversion device,
 ten chips (SR1-11 to SR1-20) on the right side (R), ten chips (IC1 to
 IC10) on the upper side (U), and ten chips (IC11 to IC20) on the lower
 side (D).
 In this configuration, 1000 wiring lines are distributed to each of the
 upper, lower, left and right sides (U, D, L and R). Therefore, the density
 of wiring lines at each side lowers. Also, the density of wire pieces for
 wire bonding at each side is lower. Accordingly, the available percentage
 of the articles of the photoelectric conversion device is enhanced. The
 control wiring lines g1, g3, g5, . . . , g1999 are distributed to the left
 side (L), while those g2, g4, g6, . . . , g2000 are distributed to the
 right side (R). That is, the odd-numbered control wiring lines are
 distributed to the left side (L), and the even-numbered control wiring
 lines to the right side (R). With such distributions, the wiring lines are
 led out and laid at equal intervals. Therefore, the wiring lines are not
 concentrated, and the available percentage is enhanced. The wiring lines
 on the upper side (U) and lower side (D) are similarly distributed.
 Each of the examples of the photoelectric conversion device shown in FIGS.
 11 and 12 may well be manufactured by forming the circuitry of the
 broken-line part on one substrate and thereafter mounting the chips on the
 substrate.
 According to this embodiment, the photoelectric conversion device of large
 area and high performance can be manufactured by a simple manufacturing
 process. That is, since the elements of the photoelectric conversion
 device are simultaneously formed using the common films or layers, the
 number of steps of the manufacturing process is small. Owing to the simple
 manufacturing process, the articles of the device can be manufactured at
 high available percentage. Therefore, the production of the photoelectric
 conversion device of large area and high performance is permitted at low
 cost. Besides, the capacitor C and the photoelectric element S can be
 formed in the identical sensor cell, and the number of elements can be
 reduced to half in substance, so that the available percentage can be
 enhanced more.
 EMBODIMENT 2
 Now, this embodiment will be described concerning a case where a
 photoelectric conversion device is applied to an X-ray imaging apparatus.
 FIGS. 13A and 13B are a schematic plan view and a schematic sectional view
 of the X-ray imaging apparatus which includes the photoelectric conversion
 device explained in Embodiment 1. The X-ray imaging apparatus is
 constructed as described below. A plurality of photoelectric elements and
 transistors are formed in an a-Si sensor substrate 6011. Besides, flexible
 circuit boards 6010 in which the shift register SR1 and the detecting
 integrated circuit IC are packaged are connected to the substrate 6011.
 The sides of the flexible circuit boards 6010 opposite to the substrate
 6011 are connected to printed circuit boards PCB1 and PCB2. A plurality of
 a-Si sensor substrates 6011 as stated above are bonded on a base 6012. The
 base 6012 for constructing the photoelectric conversion device of large
 size is underlaid with a lead plate 6013 for protecting memories 6014 in a
 processing circuit 6018 from X-rays.
 A phosphor 6030, for example, CsI (cesium iodide) for converting the X-rays
 into visible radiation or light is deposited on the a-Si sensor substrate
 6011 by coating or sticking. The X-rays are detected using the
 photoelectric conversion device explained with reference to FIG. 9. In
 this embodiment, the device is entirely received in a case 6020 made of
 carbon fiber as shown in FIG. 13B.
 FIG. 14 illustrates an example of application of the photoelectric
 conversion device of the present invention to an X-ray diagnosis system.
 X-rays 6060 generated by an X-ray tube 6050 are transmitted through the
 chest 6062 of a patient or subject 6061, and are entered into a
 photoelectric conversion apparatus 6040 including a screen of phosphor.
 Information on the interior of the body of the patient 6061 is contained
 in the entered X-rays. The phosphor phosphoresces in correspondence with
 the entrance of the X-rays, and the resulting phosphorescence is
 photoelectrically converted to obtain electrical information. The
 electrical information is digitized and is subsequently processed by an
 image processor 6070 into an image, which can be observed on a display
 device 6080 installed in a control room.
 Moreover, the image information can be sent to a remote site by
 transmission (communication) means such as a telephone line 6090. In a
 doctor room or the like in a place separate from the X-ray room or the
 control room, the sent information can be displayed on a display device
 6081, or it can be saved and stored in save means such as an optical disk.
 It is accordingly possible to utilize the system for a diagnosis by a
 doctor in the remote site. Furthermore, the sent information can be
 recorded on a film 6110 by a film processor 6100.
 As thus far described, with a photoelectric conversion device according to
 the present invention, defective transistors are vaporized away by laser
 irradiation. That is, irrespective of the patterns of sensor cells,
 defective sensor cells and signal lines can be disconnected with ease.
 Accordingly, the outputs of the sensor cells except the defective ones can
 be made to have usual values. It is therefore possible to manufacture the
 photoelectric conversion device of high S/N ratio or high resolution.
 Besides, the sensor cells can be employed as those of the photoelectric
 conversion device of large area. Thus, the photoelectric conversion device
 of large area and high performance can be manufactured at high available
 percentage by a simple manufacturing process.
 Further, a facsimile equipment or X-ray imaging apparatus of large area,
 high functions and enhanced characteristics can be provided at lower cost
 by utilizing the photoelectric conversion device having the excellent
 features as stated above.