JP2002350551A - Radiation imaging apparatus and radiation imaging system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation imaging apparatus for achieving the shooting of a still image requiring a large dynamic range, and the shooting of a dynamic image requiring an extremely high S/N ratio using the same apparatus. SOLUTION: An MIS type accumulation capacitor C1 is connected to a switch S1 so that it can be connected to the positive potential side of a power supply B1 or GND potential. By switching the switch S1, use can be made in both accumulation and depletion states. In the case of a large accumulation capacity, the accumulation capacitor C1 is used in the accumulation state to increase accumulation capacity for accumulating signal charges being generated by the sensor element in the X-ray image pickup apparatus. The accumulation capacity can be reduced by using the accumulation capacitor C1 in the depletion state to reduce the accumulation capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation imaging apparatus suitable for use in medical diagnosis and industrial nondestructive inspection. In this specification, electromagnetic waves such as X-rays and γ-rays and α
It is assumed that rays and β rays are also included in the radiation.

[0002]

2. Description of the Related Art In recent years, in the field of X-ray radiography for medical equipment, a digital image is obtained by converting an X-ray transmitted through a patient into an electric signal (charge) by converting the X-ray transmitted through the patient into an electric signal (charge). It is rapidly changing to an image processing method for processing. With digital images, image processing of X-ray images can be performed, so that diagnostic accuracy can be improved. Further, since there is no need for development, the photographing interval can be shortened, and photographing can be efficiently performed in a group checkup or the like.

[0003] In such a field, what is required is an improvement in detection sensitivity and a reduction in signal noise. In particular, if the detection sensitivity is improved, the amount of X-ray exposure at the time of imaging can be reduced and the influence on the human body can be reduced. Therefore, development of a high-sensitivity X-ray detection device is expected.

An X-ray imaging apparatus used for digital image processing is roughly classified into two types shown in FIGS. One is that an X-ray 501 carrying information passed through a patient 506 shown in FIG.
The light is transmitted to a semiconductor optical sensor 50 such as a photodiode.
4 is a method of converting into an electric signal. The other is a method shown in FIG. 12, which uses a photoelectric absorbing material 507 that absorbs X-rays and converts an X-ray signal into an electric signal by a photoelectric effect. This material includes amorphous-selenium (α-S
An amorphous material such as e) or a crystalline material such as GaAs or silicon is used. The part that transmits electric signals together
An electric circuit board 505 or 508 made of semiconductor (silicon or amorphous silicon) and having switching elements such as thin film transistors and MOS transistors and storage capacitors for storing electric signals arranged in a two-dimensional matrix is used. The former is called an indirect type, and the latter is called a direct type.

[0005] The X-ray imaging apparatus used for digital image processing is being considered for application not only to the medical field but also to measurement equipment. For example, X used for crystal analysis
When used in a line diffractometer, the process of crystal growth can be measured in real time.

[0006] The following elements are necessary for increasing the sensitivity of the X-ray detector. (A) Absorption efficiency of X-ray absorbing material (A) Volume of X-ray absorbing part (C) Transfer efficiency of generated carrier (D) Parasitic capacitance Therefore, single crystal semiconductor materials such as compound semiconductors are attracting attention. Since a single-crystal compound semiconductor can directly absorb X-rays and generate charges, the use efficiency of detected X-rays is higher than that of a configuration in which X-rays are converted to light by a phosphor or the like and then photoelectrically converted. .

[0007] However, it is said that the dynamic range of X-rays currently used in X-ray film photography is about five orders of magnitude, and in order to obtain the same image quality as that of X-ray films, the dynamic range for X-ray exposure must be increased. Must.

For this purpose, it is necessary to increase the storage capacitance for storing signal charges generated by the sensor element of the X-ray detector.

In general, the pitch at which sensor elements are arranged in an X-ray detection device is 100 to 200 μm, and thus the arrangement pattern in the X-ray detection device is 100 to 20 μm.
It is necessary to arrange at least a storage capacitor for storing the electric signal generated by the sensor element and a switching element for transferring the electric signal stored therein in the 0 μm square.

[0010] Regarding the storage capacitor for storing the electric signal generated by the sensor element and the switching element for transferring the electric signal stored therein, the capacitance value per unit area and the transfer efficiency differ depending on the thickness of the film. However,
Generally, in an area of 50 μm square, it is considered that the maximum is about 1 pF.

In such a situation, it is considered necessary to increase the storage capacity for storing the electric signal generated by the sensor element as much as possible in order to obtain an image quality equivalent to that of an X-ray film.

On the other hand, the necessity of not only still images but also moving images has been emphasized as a recent trend in medical radiography. Specifically, real-time imaging with a contrast agent such as barium, which is currently performed by a large-scale image intensifier (II), using a high-sensitivity, small-sized direct-type X-ray detection device is a worldwide standard. It is being reported in various places. In real-time imaging (moving images) of a contrast agent such as barium, only a very small radiation dose can be obtained, so that a very high S / N is required.

[0013]

However, the same apparatus is used for photographing a still image requiring a large dynamic range and for photographing a moving image requiring only a small radiation dose and requiring a very high S / N. It is said that it is difficult to achieve this.

As described above, the dynamic range of the X-ray dose of X-ray film photographing (still image) currently performed is about 5 digits, and in order to obtain image quality equivalent to X-ray film, high sensitivity and small size are required. It is necessary to increase the dynamic range of the direct X-ray imaging apparatus for the X-ray dose to be exposed, and for that purpose, it is necessary to increase the storage capacity.

However, it is difficult to configure a sufficiently large storage capacitor for storing an electric signal generated by the sensor element at a pitch at which the sensor element is arranged in a general X-ray detector, due to the electrode area and the like. is there.

On the other hand, in real-time imaging (moving images) of a contrast agent such as barium, only a very small radiation dose can be obtained, so that a very high S / N is required.
It is necessary to reduce the storage capacitance for storing the signal charges generated by the sensor element of the X-ray detection device. This is because by reducing the storage capacitance, transfer noise (generally called kTC noise) generated when the signal charge is transferred from the storage capacitance to the readout circuit can be reduced.

In order to increase the dynamic range of the X-ray imaging apparatus with respect to the X-ray exposure, the present invention provides a storage capacitor for storing signal charges generated by a sensor element of the X-ray imaging apparatus in a predetermined small area. By increasing the size, a radiographic imaging that realizes a still image radiographing that requires a large dynamic range, obtains only a small radiation dose, and realizes a moving image radiographing that requires a very high S / N with the same device. It is an object to provide an apparatus and a radiation imaging system.

[0018]

In order to solve the above-mentioned problems, the present invention provides a converter for converting radiation into an electric signal,
In a radiation imaging apparatus that includes a charge storage element that stores the converted electric signal and a transfer element that transfers the stored charge, the MIS-type storage capacitor includes a MIS-type storage capacitor that reads the transferred charge as an image signal. It is connected to a switch so that it can be connected to the positive potential or the GND potential of the power supply. By switching this switch, it can be used in both the accumulation (accumulation) state and the depletion (depletion) state.

[0019]

Next, embodiments of the present invention will be described with reference to the drawings. In the present embodiment,
An example in which a GaAs substrate is used as the X-ray direct conversion material will be described, but the present invention is not limited to this.
A substrate or a CdTe substrate may be used.

First, a direct type radiation imaging apparatus having no switch means for bringing the charge storage means into an accumulation state will be described for comparison. 4 to 10 show examples of a direct type radiation imaging apparatus. The description is given below.

FIG. 4 is an equivalent circuit diagram of one pixel of the direct type radiation imaging apparatus. Here, D1 is a GaAs sensor element that converts radiation into an electric signal, and an element that stores the electric signal detected by the sensor element is a storage capacitor C11. An amplifier (Am) that further amplifies from the storage capacitor C11
The element that transfers the electric signal to p) is the transistor T1.

Further, the radiation imaging apparatus has a configuration in which a GaAs substrate forming a sensor element and a glass substrate forming a storage capacitor C11 and a transfer transistor T1 are joined with a conductive adhesive. Therefore, the junction resistance between the GaAs substrate and the glass substrate is defined as r1, and the sensor part R1 is determined by combining the sensor element D1 and the junction resistance with r1.
And is indicated by a broken line in FIG.

FIG. 5 is a schematic sectional view of a pixel portion of the radiation imaging apparatus in FIG.

Here, each of the elements described with reference to FIG. 4 includes a sensor section corresponding to the sensor section R1 including the sensor element D1 and the junction resistance r1, a storage capacitor corresponding to the storage capacitor C11, and a transfer element. Transistor T1
Is equivalent to the transistor 4.

The common electrode 1 of the GaAs substrate 2 is
an electric signal converted by the aAs sensor element, that is, a charge collecting electrode 3 for collecting electric charges, and a GaAs substrate 2
FIG. 1 shows a conductive adhesive 5 for electrically connecting the substrate and the glass substrate 10, and a bonding electrode 6 connected to a transistor 4 for controlling reading of an electric signal from a storage capacitor.

The layer structure of the storage capacitor and the transistor 4 formed on the glass substrate 10 is as follows: the first metal layer is 9; the insulating layer deposited thereon is 8; The intrinsic semiconductor layer 7 is deposited.

The storage capacitance C11 described in FIG. 4 and the storage capacitance in FIG. 5 are MIS type capacitors.
The constant potential electrode 9 in FIG. 5 is always used in a depletion state because it is grounded.

FIG. 6 is a characteristic diagram showing a capacitance value with respect to a potential difference of a common electrode of the MIS type capacitor in FIG. Here, the potential difference Vg of the counter electrode is represented by the potential of the constant potential electrode 9 with respect to the potential of the bonding electrode 6 in FIG.

As shown in FIG. 6, in the MIS type capacitor, when Vg is made negative, the depletion region expands in the intrinsic semiconductor layer 7 and becomes constant at a small capacitance value (region 23: depletion state). When Vg is made positive, charges (electrons) are injected into the semiconductor layer, the depletion region becomes narrower, and the capacitance value gradually increases (region 22). When the depletion region disappears, only the insulating layer becomes the dielectric of the capacitor. The capacitance value is constant at a large value (area 21: accumulation state).

FIG. 7 is a schematic equivalent circuit diagram of a direct type radiation imaging apparatus. The description is given below.

The device has 2000 × 2000 pixels and has 2000 × 2000 sensor elements and 200 pixels.
0 × 2000 transfer elements (thin film transistor: TF
T). Further, an X-ray two-dimensional sensor and a power source 103 each including a vertical drive circuit 104 for driving the TFT connected to the TFT, a reading circuit 100 for reading a signal output from the TFT, and an X-ray two-dimensional sensor And a computer 105 that receives the signal output from the X-ray two-dimensional sensor, displays and stores it as a two-dimensional image, corrects the image, and controls the X-ray two-dimensional sensor.

To obtain a two-dimensional X-ray image, a voltage of +15 V is applied to one gate line, and the gate lines (g1 to g2000)
Is turned on, and the electric signal accumulated in the capacitor from the sensor element is transferred to the signal transfer line (Sig1).
Through Sig2000) to the sample and hold circuit 102 of the reading circuit 100. Signal transfer is for a fixed time TF
After turning on T, -5V is applied to the gate line to make T
The FT is turned off and the process ends.

Further, signals are sequentially transferred from the sample and hold circuit by the multiplexer 101. By sequentially repeating this operation, an X-ray two-dimensional image can be obtained.

Also in this example, since the capacitor for storing the electric signal is of the MIS type, and the constant potential electrode is grounded, it is always used in a depletion (depletion) state.

FIG. 8 is still another example of the direct type radiation imaging apparatus. FIG. 8 is a cross-sectional view of two pixels of the direct type radiation imaging apparatus.
3 shows a layer configuration of FT. The description is given below.

For the sensor element shown in FIG. 8, semiconductors such as silicon (Si), gallium arsenide (GaAs), and gallium phosphide (GaP) can be used.
This will be described with reference to FIG.

As a sensor element, a GaAs wafer is used. First, a protective layer 201, aluminum (Al)
An upper electrode layer 202 formed of a metal material such as
P + type GaAs layer 203 for making ohmic contact between the GaAs substrate and the upper substrate, photoelectric conversion layer 204 for generating carriers by photoelectric effect, n type GaAs layer 2
05, an n + -type GaAs layer 206 for making ohmic contact with the lower connection electrode, and a lower connection electrode 207 formed of a metal electrode such as aluminum.
It is an IN type diode.

First, an n-type GaAs layer 300 is formed on a semi-insulating GaAs substrate or a lightly doped p-type GaAs substrate.
0 °, n + type GaAs layer at 1000 °, molecular beam epitaxy (MBE) or liquid phase epitaxy (LPE)
Then, patterning is performed by lithography and etching is performed in a shape corresponding to each electrode.
Further, a silicon nitride film (SiNx) is deposited to a thickness of 1 μm by a chemical vapor deposition method (CVD method) to protect the surface. Next, a p-type GaAs layer is formed on the opposite surface of the substrate by molecular beam epitaxy (MBE) or liquid phase epitaxy (LPE).
A metal layer such as aluminum is deposited in order of 1 μm by sputtering. The silicon nitride film on the side on which the n-type GaAs layer is deposited is opened by etching, and a metal layer such as aluminum serving as a lower connection electrode is made 1 μm thick by sputtering or the like.
accumulate. Further, after patterning by lithography, unnecessary portions are etched to form electrodes.

The lower electric circuit board has a storage capacitor and a thin film transistor (TFT) as a switching element on a substrate 210 having at least an insulating surface.
It is composed of wiring and the like for transferring signals. The layer structure is such that a lower electrode 211 of a storage capacitor made of chromium (Cr) or the like, a gate electrode 216 of a TFT, and an amorphous silicon nitride (a-
SiNx) layers 212 and 217, hydrogenated amorphous silicon (a-Si: H) layers 213 and 218 serving as TFT channel layers and dielectric layers of storage capacitors, and n + type a- for obtaining ohmic contact of upper electrodes. Si: H
Layers 214 and 219, upper electrode of storage capacitor and T
It is composed of electrode layers 215 and 220 made of a metal such as Al serving as a source electrode and a drain electrode of the FT, an a-SiNx layer 221 serving as a protective layer, and an upper connection electrode layer 222 for connection with a photoelectric conversion layer. . The upper connection electrode layer is
It is connected to the lower electrode of the storage capacitor via the contact hole.

On a substrate having at least an insulating surface, C
A metal such as r is formed to a thickness of 1000 ° by a sputtering method. After patterning by lithography, etching is performed to separate the lower electrode of the storage capacitor and the gate electrode of the TFT. Next, an a-SiNx layer 3000 # serving as an insulating layer,
a-Si: H layer 3000 #, n-type a-Si: H layer 750
Å Deposit sequentially by CVD method. After patterning by lithography, reactive ion etching (RIE)
Etching, separating into a storage capacitor and TFT,
Further, a contact hole for connecting the TFT and the storage capacitor is formed by RIE.

After 1 μm of Al is deposited by sputtering and patterned by lithography, etching is performed to separate the source electrode and drain electrode of the TFT, the upper electrode of the storage capacitor, and the signal transfer wiring.

An a-SiNx serving as a protective layer is deposited by the CVD method, and a contact hole for connecting the lower electrode and the upper connection electrode is formed by RIE using RIE.
Furthermore, after a metal layer of Al or the like serving as an upper connection electrode is deposited by a sputter or the like and patterned by lithography, unnecessary portions are etched by RIE to form an upper connection electrode layer.

FIG. 8 shows only two pixels.
Actually, many pixels are formed simultaneously. The thickness of each layer is not limited to this, and an optimal film thickness is used.

As a method of connecting the sensor element and the TFT, a bump 208 is formed on the sensor element, and the two are electrically connected with an anisotropic conductive adhesive. The bump is made of gold (A
u) After forming a barrier metal made of 1 μm, palladium (Pd) and titanium (Ti), an Au bump having a height of 15 μm is formed.

FIG. 9 is a schematic view of the sensor element of the GaAs substrate, and FIG. 10 is a schematic view of the lower electric circuit board as viewed from the connection side of both.

As shown in FIG. 9, the carrier supply electrodes 309 of the sensor element are in the shape of an interdigital transducer, and are all supplied with the same potential. The voltage is supplied from the TFT via the connection portion 310 on the carrier supply electrode.

As shown in FIG. 10, the lower electric circuit board has a pixel formed of a TFT 407 and a storage capacitor 408 and a gate bias line (400 to 402) for supplying a bias to a gate electrode of the TFT, and a signal output from the TFT. Signal transfer line (4) for transferring the electrical signal to the readout circuit.
03 to 405), an electrode 406 connected to the upper electrode of the storage capacitor for fixing the potential, a carrier supply electrode lower connection portion 409 connected to the sensor element and applying a voltage to the carrier supply electrode 309, and the like. .

The electrode 406 and the gate electrode (400 to 40
2) is formed of the same material as the lower electrode of the storage capacitor, and the signal transfer lines (403 to 405) are formed of the same material as the upper electrode of the storage capacitor, and are formed when forming the lower electrode and the upper electrode, respectively.

Although FIGS. 9 and 10 show an example of 3 × 3 pixels, the actual number of pixels is not limited to this. Also, T
Although the method of supplying a voltage from the FT to the carrier supply electrode has been described, a method of directly connecting the sensor element to a power supply by some method may be used.

Here, the configuration of the present invention will be described. FIG.
FIG. 3 is an equivalent circuit diagram of one pixel of the direct radiation imaging apparatus according to the embodiment of the present invention. Here, components having the same functions as those in FIG. 4 are given the same numbers. D1 is a GaAs sensor element for converting radiation into an electric signal, and an element for storing the electric signal detected by the sensor element is a storage capacitor C1.
It is. Further, from the storage capacitor C1 to the amplification amplifier (Amp)
An element that transfers an electric signal to the transistor T1 is a transistor T1.
The constant potential electrode of the storage capacitor C1 is connected to the power source B1.
Is connected to the positive potential side.

Further, the radiation imaging apparatus of the present invention has a configuration in which the GaAs substrate forming the sensor element and the glass substrate forming the storage capacitor C1 and the transfer transistor T1 are joined with a conductive adhesive, so that the GaAs substrate and the GaAs substrate are joined together. The junction resistance with the glass substrate is represented by r1, and the sensor element D1
It is shown by a broken line a contact resistance in FIG. 1 as the sensor portion R1 together with r ₁ and is the same as FIG.

A schematic sectional view of a pixel portion of the radiation imaging apparatus in FIG. 1 is similar to FIG. Therefore, the description of the same portions as those described above will be omitted, and the difference between FIGS. 1 and 4, that is, the configuration of the present invention will be described.

The storage capacitor C1 in FIG. 1, the storage capacitor C11 in FIG. 4, and the storage capacitor in FIG. 5 are MIS-type capacitors, and change between an accumulation (accumulation) state and a depletion (depletion) state depending on the potential of both electrodes. The characteristics shown in FIG. Depletion (depletion) because the constant potential electrode in FIG. 5 is grounded
It will always be used in the state. On the other hand, in the configuration of the present invention, since the switch S1 is connected so that it can be connected to the positive potential side of the power supply B1 or the GND potential, the accumulation (accumulation) state and the depletion ( It can be used in both depletion) states.

With this configuration, when it is desired to increase the storage capacity, for example, when photographing a still image, the switch S1 is switched, the storage capacity C1 is connected to the positive potential of the power supply B1, and the storage capacity C1 is accumulated ( By using in the (accumulated) state, it is possible to increase the accumulated capacitance for accumulating the signal charges generated by the sensor element of the X-ray imaging apparatus. Therefore, X-ray imaging device
The dynamic range with respect to the dose can be increased, and it is possible to obtain the same image quality as that of the currently performed radiography (still image).

When it is desired to reduce the storage capacity, for example, when shooting a moving image, the switch S1 is switched to connect the storage capacity C1 to the GND potential, and the storage capacity C1
By using in a depleted state,
It is also possible to reduce the storage capacity. Therefore, transfer noise (kTC noise) generated when the signal charge is transferred from the storage capacitor to the readout circuit can be reduced, a small radiation dose can be obtained, and a very high S / N is required. It is also possible to obtain image quality equivalent to real-time imaging (moving image) using a contrast agent such as barium.

That is, in the present invention, a still image photographing that requires a large dynamic range and a moving image photographing that requires only a very small radiation dose and requires a very high S / N are, for example, the first method. For example, an operator or the like can appropriately select one of two modes, in which the charge storage element is in a depletion state and a moving image is captured, and the second mode is a still image in which the charge storage element is in an accumulation state. (First Embodiment) FIG. 2 is an equivalent circuit diagram of a direct radiation imaging apparatus according to a first embodiment of the present invention. Here, components having the same functions as those in FIG. 7 are denoted by the same reference numerals.

In this embodiment, a plurality of sensor elements are arranged in a matrix on a substrate, and one of the electrodes of the charge storage element is connected to a switch 107 so that the power supply 106 can be connected to a positive potential or a GND potential. Therefore, by switching the switch 107, it can be used in both the accumulation (accumulation) state and the depletion (depletion) state.

When the storage capacity is to be increased, the switch 107 is switched and the capacitor is connected to the power supply 1.
06 positive potential and using the MIS-type storage capacitor in the accumulation (accumulation) state to simultaneously increase the storage capacity of all pixels and reduce the signal charge generated by the sensor element of the X-ray imaging apparatus. It is possible to increase the storage capacity to be stored. Therefore, the dynamic range of the X-ray imaging apparatus with respect to the exposed X-ray can be increased, and a dynamic range of X-ray equivalent to that of the currently performed X-ray film photographing (still image) can be obtained. It is possible to obtain the same image quality as.

When it is desired to reduce the storage capacitance, the switch 107 is switched, the capacitor is connected to the GND potential, and the MIS type storage capacitance is used in a depletion (depletion) state. It is also possible to do. Therefore, transfer noise (kTC noise) generated when the signal charge is transferred from the storage capacitor to the readout circuit can be reduced, a small radiation dose can be obtained, and a very high S / N is required. It is also possible to obtain image quality equivalent to real-time imaging (moving image) using a contrast agent such as barium.

That is, in the present invention, a still image photographing requiring a large dynamic range and a moving image photographing requiring only a very small radiation dose and requiring a very high S / N are realized by the same apparatus. It becomes possible. Also in the present embodiment, by appropriately selecting the two modes of the moving image (depression state) and the still image (accumulation state) by the operator, it is possible to preferably perform the photographing of both the still image and the moving image with one apparatus. it can. (Second Embodiment) Next, a second embodiment of the present invention will be described. The present embodiment is an X-ray imaging system using the X-ray imaging device of the present invention. FIG. 3 is a configuration diagram of the X-ray imaging system of the present embodiment. The X-ray imaging system according to the present embodiment includes an X-ray generation device 31, an X-ray imaging device (X-ray sensor) 32 described in the first embodiment, and is connected to these, and converts a signal from the X-ray sensor 32 into a digital signal. It is composed of a workstation 33 for converting and performing image processing.
The workstation 33 has a function of switching and setting a shooting mode by shooting a still image or a moving image, a function of controlling the driving of the X-ray generator 31 and the X-ray sensor 32 according to the set shooting mode, and the like. And a function of displaying an image.

When the moving image shooting mode or the still image shooting mode is input to the workstation 33, the switch 10
By switching 7, the MIS type capacitor is set to a depletion (depletion) state or an accumulation (accumulation) state. That is, when the moving image shooting mode is set, the switch 107 is switched to be connected to the GND potential, and the capacitors of all the pixels are in a depletion (depletion) state. When the mode is set to the still image shooting mode, the switch 107 is switched to connect the power supply 106 to the positive potential, and the capacitors of all pixels are accumulated (accumulated).
State.

With the above configuration, it is possible to realize, with the same apparatus, the photographing of a still image that requires a large dynamic range and the photographing of a moving image that requires only a very small radiation dose and requires a very high S / N. It becomes possible. For this reason, the subject (subject) 30 can be X-ray diagnosed by moving image shooting, and a portion where an abnormality is found is shot by still image shooting to obtain a clearer image and used for subsequent diagnosis. Becomes

[0063]

As described above, according to the present invention, when it is desired to increase the storage capacity for storing the signal charges generated by the sensor element of the radiation imaging apparatus, the accumulation capacity of the MIS type storage capacity is accumulated. By using in this state, it is possible to simultaneously increase the storage capacity of all pixels. Therefore, in the case of the X-ray imaging apparatus, the dynamic range with respect to the X-ray dose can be increased, and the dynamic range with the same X-ray dose as the radiography film (still image) currently performed can be obtained. Image quality equivalent to that of an X-ray film can be obtained.

When it is desired to reduce the storage capacitance, the switch is switched to use the MIS type storage capacitance in a depletion (depletion) state, whereby the storage capacitance of all pixels can be reduced at the same time. Therefore, transfer noise (kTC noise) generated when the signal charge is transferred from the storage capacitor to the readout circuit can be reduced, a small radiation dose can be obtained, and a very high S / N is required. It is also possible to obtain image quality equivalent to real-time imaging (moving image) using a contrast agent such as barium.

That is, in the present invention, the same apparatus can be used to capture a still image that requires a large dynamic range and a moving image that requires only a very small radiation dose and requires a very high S / N. It becomes possible.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram illustrating one pixel of an X-ray imaging apparatus according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram illustrating an X-ray imaging apparatus according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of an X-ray imaging system using the X-ray imaging device of the present invention.

FIG. 4 is an equivalent circuit diagram showing one pixel of the X-ray imaging device that we previously proposed.

FIG. 5 is a sectional view of FIG. 4;

FIG. 6 is a CV characteristic diagram of the MIS capacitor.

FIG. 7 is an equivalent circuit diagram showing an X-ray imaging device we previously proposed.

FIG. 8 is a cross-sectional view showing an X-ray imaging device that we previously proposed.

FIG. 9 shows Ga in an X-ray imaging apparatus previously proposed by us.
It is the schematic diagram which looked at the sensor element of the As board | substrate from the connection side.

FIG. 10 shows the X-ray imaging apparatus we previously proposed.
It is the schematic diagram which looked at the lower electric circuit board from the connection side.

FIG. 11 is a schematic diagram of an indirect X-ray imaging apparatus.

FIG. 12 is a schematic diagram of a direct X-ray imaging apparatus.

[Explanation of symbols]

B1 power supply C1, C11 storage capacitance D1 GaAs sensor element r1 junction resistance R1 GaAs sensor section S1 switch T1 transfer transistor 1 common electrode of GaAs substrate 2 GaAs substrate 3 charge collection electrode of GaAs substrate 4 transistor 5 GaAs substrate and glass substrate Conductive adhesive for electrical connection (junction resistance) 6 Junction electrode connected to transistor and storage capacitor 7 Intrinsic semiconductor layer 8 Insulating layer 9 Metal layer (constant potential electrode) 10 Glass substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/335 H01L 27/14 AK F term (Reference) 2G088 EE01 EE29 FF02 FF04 FF05 FF06 GG21 JJ05 4M118 AA02 BA05 CA02 CA32 CB02 CB11 FB03 FB09 FB13 FB16 FB17 FB22 HA31 5C024 AX11 CX43 CY11 GX03 GX18 GY31 HX35 HX50 5F088 AB02 AB07 BA03 BB03 CB02 CB03 EA04 KA08 KA10 LA07 LA08

Claims (10)

[Claims] 1. A radiation device comprising: a converter for converting radiation into electric charge; a charge storage element for storing the converted electric charge; and a transfer element for transferring the stored electric charge, and reading the transferred electric charge as an image signal. In the imaging device, the charge storage element is a MIS-type capacitor;
A radiation imaging apparatus, wherein the MIS-type capacitor has a switch means for setting a potential at which the MIS-type capacitor is brought into an accumulation (accumulation) state. 2. The radiation imaging apparatus according to claim 1, wherein the imaging is performed in a state where the charge storage element is in an accumulation (accumulation) state. 3. The radiation imaging apparatus according to claim 1, wherein said switch means is connected to a plurality of said charge storage elements. 4. The radiation imaging apparatus according to claim 1, wherein said converter is made of silicon or gallium arsenide. 5. The radiation imaging apparatus according to claim 1, wherein the intrinsic semiconductor layer of the charge storage element is made of amorphous silicon. 6. The transfer element comprises a thin film transistor (T)
6. The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus is FT) and the intrinsic semiconductor layer is amorphous silicon. 7. The radiation imaging apparatus according to claim 6, wherein the charge storage element and the transfer element have the same film configuration and are formed by the same process. 8. The radiation imaging apparatus according to claim 1, wherein a plurality of the converters are arranged in a matrix. 9. At least a first mode for capturing a moving image and a second mode for capturing a still image, wherein the charge storage element is in a depletion state in the first mode. 2. The radiation detecting apparatus according to claim 1, wherein the charge storage element is in an accumulation (accumulation) state in the second mode. 10. A radiation source for irradiating a subject or a test object with radiation, the radiation imaging apparatus according to claim 1, and image processing for digitally converting a read signal and performing image processing. A radiation imaging system, comprising: means for displaying a processed image.