JP2003179220A - X-ray plane detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray plane detector which prevents a pixel circuit from becoming complicated for protective action against a high voltage and which can acquire a satisfactory image even when a pixel is made fine. <P>SOLUTION: The X-ray plane detector is provided with an X-ray photosensitive film which generates signal charges photosensitized by incident X-rays, a plurality of pixel electrodes which are arranged so as to be adjacent to the X-ray photosensitive film, a voltage application means by which a bias voltage is applied to the photosensitive film in such a way that holes or electrons of higher mobilities from among holes and electrons as the signal charges generated by the photosensitive film are collected to the plurality of pixel electrodes, capacitors which are installed at the pixel electrodes and which store the signal charges generated by the photosensitive film, a plurality of switching TFTs which are installed at the pixel electrodes and which read out the signal charges stored in the capacitors, a plurality of scanning lines which supply control signals used to on-off-control the plurality of TFTs and a plurality of signal wires which are connected to the plurality of switching TFTs and which read out the signal charges when the switching TFTs are turned off. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray flat panel detector used in a medical X-ray diagnostic apparatus or the like, and more particularly, an X-ray detector using a thin film transistor as a switching element provided in a two-dimensionally arranged X-ray detection pixel. It relates to a line plane detector.

[0002]

2. Description of the Related Art In recent years, an X-ray flat panel detector for electrically detecting an X-ray image has been developed as one of X-ray diagnostic apparatuses. In this X-ray flat panel detector, X-ray photosensitive pixels that generate signal charges by X-ray irradiation are two-dimensionally arranged. The signal charge generated in each photosensitive pixel by the incident X-ray is stored in the signal charge storage section, and the signal charge is read out by the thin film transistor as a switching element.

FIG. 13 shows a circuit configuration of one pixel of this X-ray flat panel detector. As shown in FIG. 13, each pixel 101 has a plurality of pixels 101 arranged in an array.
Is a thin film transistor (hereinafter referred to as TFT) 102 made of amorphous silicon (hereinafter referred to as a-Si) used as a switching element, an X-ray photosensitive film 103 made of Se, and a pixel capacitance (hereinafter referred to as Cst) 10
4 and the protection TFT 111. Cs
At t104, the Cst bias line 105 is connected.

The switching TFT 102 has a gate connected to the scanning line 107 and a source connected to the signal line 108. The switching TFT 102 is on / off controlled by the scanning line drive circuit 109. Signal line 108
Is connected to the amplifier 110 for signal detection. The source and the gate of the protection TFT 111 are connected to the drain of the switching TFT 102, and the drain is connected to the power supply 113 through the bias line 112. The protective TFT 111 may not be provided in some cases.

When an X-ray is incident, the X-ray is exposed to the X-ray photosensitive film 10.
The electric charges are converted into electric charges by 3, and the electric charges are accumulated in Cst104. When the scanning line 107 is driven by the scanning line driving circuit 109 and one row of the switching TFTs 102 connected to one scanning line 107 is turned on, Cst
The charges accumulated in 104 are transferred to the amplifier 110 side through the signal line 108. The charges transferred to the amplifier 110 side are amplified by the amplifier 110, subjected to predetermined processing, and then converted into dot-sequential signals that can be displayed on a CRT or the like. Since the amount of electric charge varies depending on the amount of X-rays that enter the pixel 101, the output amplitude of the amplifier 110 varies. Further, in order to prevent excessive accumulation of charges in Cst104, charges above the bias voltage are released from the bias line 112 by the protective TFT 111. However, the existence of such a protection circuit for protecting the protection TFT 111 or the like causes the following problems, for example. First, the pixel circuit becomes complicated and TF
The yield of non-defective T array substrates decreases. Second
In addition, if the number of pixels is increased and the pixel size is reduced in order to increase the resolution, it becomes difficult to draw out the wiring from the protection TFT 111, the switching TFT 102, etc. at a sufficiently narrow pitch. Thirdly, since the area of the protective TFT 111 occupying the miniaturized pixel is large, Cst104
Cannot secure enough area.

Further, it has been found that the following problems occur when the number of pixels is increased to increase the resolution and the pixel size is miniaturized. The switching TFT 10
2, X-ray photosensitive film 103, Cst104, and protective TF
These wirings are connected to the TFT array substrate on which T111 and the like are arranged in order to externally attach a driving circuit for driving the switching TFT and a TAB on which an LSI for reading out a signal is mounted outside the detection pixel area. There is a need. At this time, if the pixel size is reduced, it becomes difficult to connect the wirings at a sufficiently narrow pitch. In addition, the area ratio of the TFT in the miniaturized pixel is too large, and the area of the signal storage capacitor cannot be sufficiently obtained. Further, as the number of pixels increases, the signal reading time per line becomes shorter, but the TFT provided in a-Si cannot sufficiently read the signal in this short address time. Therefore, in the conventional X-ray flat panel detector, particularly in the X-ray flat panel detector using a-SiTFT, if the pixels are miniaturized to increase the resolution and the number of pixels is increased, the driving capability of the TFT is insufficient, which is preferable. There is a problem that a detected image cannot be obtained.

Further, it is important for a medical X-ray detector to be able to make a diagnosis with as low an X-ray dose as possible in order to suppress the influence on the human body. For this purpose, it is important to reduce the off-current of the switching TFT in order to detect the minute charge generated with a low X-ray dose. On the other hand, good image quality is necessary for accurate diagnosis. In this case, it is necessary to capture an image with a high X-ray dose and a good SN ratio. Therefore, it is preferable to be able to capture an image from a weak X-ray to a strong X-ray dose. For this purpose, it is necessary that the switching TFT normally operates even for a high pixel voltage corresponding to a large electric charge.
Further, it is necessary to reduce the off current of the switching TFT. Further, in the switching TFT used in such an X-ray flat panel detector, defects are often generated due to X-ray irradiation and the characteristics are deteriorated.
TFT characteristics are required so that T can operate even after deterioration.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents the pixel circuit from becoming complicated due to the protection action against a high voltage, and miniaturizes the pixel to reduce the number of pixels. An object of the present invention is to provide an X-ray flat panel detector capable of acquiring a good image even when the number of various wirings is increased.

[0009]

The present invention takes the following means in order to achieve the above object.

According to a first aspect of the present invention, there is provided an X-ray photosensitive film which is exposed to incident X-rays to generate signal charges, and the X-ray photosensitive film.
Of a plurality of pixel electrodes two-dimensionally arranged in contact with the X-ray photosensitive film and holes and electrons as signal charges generated in the X-ray photosensitive film, whichever has a higher mobility is set to the plurality of pixel electrodes. Bias voltage applying means for applying a bias voltage to the X-ray photosensitive film so as to be collected, a plurality of capacitors provided for each of the pixel electrodes for accumulating charges generated by the X-ray photosensitive film, and the pixel. A plurality of switching thin film transistors which are provided for each electrode and read out charges accumulated in the capacitor, a plurality of scanning lines which supply a control signal for controlling opening and closing of the plurality of switching thin film transistors, and the plurality of switching thin film transistors. And a plurality of signal lines for reading the electric charges when the switching thin film transistor is closed. An X-ray flat panel detector characterized by and.

According to a ninth aspect of the present invention, there is provided an X-ray photosensitive film which is exposed to incident X-rays to generate signal charges, and the X-ray photosensitive film.
Of a plurality of pixel electrodes two-dimensionally arranged in contact with the X-ray photosensitive film and holes and electrons as signal charges generated in the X-ray photosensitive film, whichever has a higher mobility is set to the plurality of pixel electrodes. Bias voltage applying means for applying a bias voltage to the X-ray photosensitive film so as to be collected, a plurality of capacitors provided for each of the pixel electrodes for accumulating charges generated by the X-ray photosensitive film, and the pixel. A plurality of switching thin film transistors which are provided for each electrode and which use a hole or electron as a signal charge generated in the X-ray photosensitive film having higher mobility as a carrier and read out charges accumulated in the capacitor; A plurality of scanning lines supplying a control signal for controlling the opening and closing of a plurality of switching thin film transistors, and connected to the plurality of switching thin film transistors, Serial is an X-ray flat panel detector having a plurality of signal lines for reading out the charges when the switching thin film transistor is closed.

According to a sixteenth aspect of the present invention, the mobility of holes is higher than that of electrons, and the incident X
X-ray photosensitive film which is exposed to a line to generate a signal charge, a plurality of pixel electrodes which are two-dimensionally arranged in contact with the X-ray photosensitive film, and holes as a signal charge generated in the X-ray photosensitive film. So as to be collected in the plurality of pixel electrodes, bias voltage applying means for applying a bias voltage to the X-ray photosensitive film, and a charge voltage generated by the X-ray photosensitive film, which is provided for each pixel electrode. A plurality of p-channel thin film transistors having a plurality of capacitors and a polycrystalline silicon film provided on the insulating substrate for each of the pixel electrodes and provided in an island shape on the insulating substrate, for reading signal charges accumulated in the capacitors. A plurality of scan lines that supply a control signal for controlling the opening and closing of the plurality of p-channel thin film transistors, and the p-channel thin film transistor connected to the plurality of p-channel thin film transistors. An X-ray flat panel detector having a plurality of signal lines for reading out the signal charge when the thin film transistor is closed.

According to a twentieth aspect of the present invention, a material having a higher electron mobility than a hole mobility is used, and the incident X
An X-ray photosensitive film that is exposed to rays to generate electrons and holes; a plurality of pixel electrodes that are two-dimensionally arranged in contact with the X-ray photosensitive film; A plurality of capacitors for accumulating electrons generated by the film, a plurality of n-channel thin film transistors provided for each of the pixel electrodes to read out the electrons accumulated by the capacitors, and a control signal for controlling opening / closing of the plurality of n-channel thin film transistors. A plurality of scan lines for supplying
An X-ray flat panel detector comprising a plurality of signal lines connected to a channel thin film transistor and for reading out the electrons when the n channel thin film transistor is closed.

According to a twenty-fourth aspect of the present invention, there is provided an X-ray photosensitive film which is exposed to incident X-rays to generate signal charges, and a plurality of pixel electrodes which are two-dimensionally arranged in contact with the X-ray photosensitive film. Bias voltage applying means for applying a bias voltage to the X-ray photosensitive film, and the X
A plurality of capacitors for accumulating charges generated by the line photosensitive film, a plurality of polycrystalline silicon p-channel thin film transistors provided for each pixel electrode for reading out charges accumulated by the capacitors, and a plurality of the switching elements. A plurality of scanning lines for supplying a control signal for controlling the opening / closing of the thin film transistor, and a plurality of signal lines connected to the plurality of switching thin film transistors for reading the charges when the switching thin film transistor is closed; An X-ray flat panel detector comprising:

According to such a configuration, the pixel circuit is prevented from becoming complicated due to the protection action against a high voltage, and an X-ray flat panel detector capable of obtaining a good image even if the pixel is miniaturized is realized. be able to.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First to third embodiments of the present invention will be described below with reference to the drawings. In the following description, constituent elements having substantially the same functions and configurations are designated by the same reference numerals, and redundant description will be given only when necessary.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
2 is a circuit diagram showing a basic configuration of an X-ray flat panel detector according to the embodiment of FIG. As shown in FIG. 1, an X-ray detection pixel 1 for converting an incident X-ray into an electric signal is two-dimensionally arranged to form an imaging region 2. The pixel 1 includes an X-ray photosensitive film 1a that converts an incident X-ray into an electric signal, a pixel electrode 1b connected to the X-ray photosensitive film 1a, and a storage capacitor 1 connected to the pixel electrode 1b.
c, a switching thin film transistor (TFT) 1d whose source is connected to the pixel electrode 1b. Figure 1
Shows a 2 × 2 pixel configuration for simplification, but in reality, it has an m × n pixel configuration with more rows and columns.

One of the important points of the present invention is that the X-ray photosensitive film 1 is used.
The direction of the bias voltage applied to the X-ray photosensitive film 1a is selected according to the type of a. That is, when using the X-ray photosensitive film 1a in which the hole mobility is higher than the electron mobility, a bias voltage is applied to the X-ray photosensitive film 1a in the direction in which holes are collected in the pixel electrode. Apply. On the other hand, when an X-ray photosensitive film having electron mobility higher than hole mobility is used, a bias voltage is applied to the X-ray photosensitive film 1a in the direction in which electrons are collected in the pixel electrode. . In each of the following embodiments, for the sake of concrete description, an X-ray flat panel detector using an X-ray photosensitive film 1a having a hole mobility higher than an electron mobility is taken as an example.

In the image pickup area 2, a plurality of scanning lines 3 and a plurality of signal lines 4 are arranged so as to be orthogonal to each other. The scanning line 3 is a switching TFT in the imaging area 2.
It is connected to a gate 1d and is connected to a gate driver 5 for selectively driving pixels outside the imaging region 2.
In addition, the signal line 4 is a switching TF in the imaging area 2.
It is connected to the drain of T1d, and is read out by the readout circuit 7 outside the imaging region 2 and output.

FIG. 2 is a plan view showing the structure of the pixel 1.
FIG. 3 is a cross-sectional view showing the configuration of the pixel 1 (3B-3B in FIG. 2).
Is a cross section along). SiNx (50 nm) / SiO as an undercoat insulating film 11 on the glass substrate 10.
₂ (100 nm) is formed and amorphous Si is formed on it.
An (a-Si) film is formed with a film thickness of 50 nm.

Subsequently, the a-Si film is polycrystallized by ELA (Excimer Laser Annealing) to form a polycrystal Si (p-Si) film 12 of 50 nm. Then, the p-Si film 12 is etched to form an island 12-1 in the transistor region and an island 12-2 in the capacitor region.
To form. Then, a gate SiO ₂ film 13 is formed to a thickness of 150 nm by PCVD or thermal CVD. Next, the gate electrode 14-1 is formed on the island 12-1 in the transistor region, the gate electrode 14-2 is formed on the island 12-2 in the capacitor region, and M
It is formed with a thickness of 300 nm as an OW gate.

Next, by ion implantation using the gate electrode or the resist as a mask, B is added at 1 × 10 ¹⁴ cm ^{−2 to} 5 ×.
10 ¹⁶ cm ^-2 , preferably 1 x 10 ¹⁵ cm ^-2 to 1 x 10
¹⁶ cm ^-2, and heavily doped of 3 × 10 ¹⁵ cm ^-2 in this embodiment, to form the p ⁺ region 15. That is, the drain 15-1 and the source 1 which are p ⁺ regions in the transistor region
5-2 is formed, and the p ⁺ region 15-3 is formed in the capacitor region. Here, the gate width W and the gate length L are set to W / L = 10/5 μm, for example.

Then, a SiO ₂ film 16 is formed as an interlayer insulating film.
To a thickness of 500 nm by PCVD. Next, a hole is formed in the source / drain contact portion of the SiO ₂ film 16 to remove Mo.
/ Al / Mo film 17 allows drain 15d of TFT 1d
Signal line 17-1 connected to 1 and source 1 of TFT 1d
5-2 and the Cs line 17-2 connected to the p ⁺ region 15-3 of the storage capacitor 1c and the capacitance line 17- connecting the storage capacitor
3 is formed. Next, a SiNx film (not shown) for passivation is formed by PCVD to a thickness of 400 nm. After that, an acrylic resin is coated in an amount of 2 to 5 μm, preferably 3 μm to form the protective film 18. Then, the contact portion is exposed and developed using an acrylic photosensitive resin. Next, an ITO film is formed to a thickness of 100 nm and is patterned into a desired shape to form an ITO pixel electrode 19.

Then, as the X-ray photosensitive film 1a, p-type S
The e-layer 21, the i-type Se layer 22, and the n-type Se layer 23 are formed in the above order. Specifically, the p-type Se or p-type As ₂ Se ₃ film 21 is formed on the TFT array substrate by vapor deposition of 5 to 100 μm, preferably 10 μm. An undoped high-resistance Se film 22 having a thickness of 900 μm is formed thereon. Then, an n-type Se film 23 is deposited thereon in an amount of 5 to 100 μm, preferably 1
0 μm is formed. And, Cr is 100 nm on the top,
Al is vapor-deposited to a thickness of 300 nm to form the upper electrode 25.
500 steps for manufacturing on glass substrate
It is formed at a temperature of ℃ or below, and is optimized as a TFT array. Therefore, it has a characteristic different from that of p-Si used in a barricade LSI at a high temperature.

The X-ray photosensitive film 1a has a hole mobility of
If it is made of a photosensitive material having a higher electron mobility,
If it is, it may be anything. As a typical example,
Examples include photosensitive materials such as GaP, AlSb, and a-Se.
It On the other hand, X-rays in which electron mobility is higher than hole mobility
The material of the photosensitive film is CdZnTe, CdSe, Hg
I _Two, PbI_Two, ZnTe, CdTe, CdS, etc.
To be

The upper electrode 25 is formed on the X-ray photosensitive film 1a.
A bias voltage is applied to the pixel electrode 1b so that the hole or electron having the higher mobility is collected by the pixel electrode 1b.
In this case, since the X-ray photosensitive film 1a uses a photosensitive material in which hole mobility is higher than electron mobility, the upper electrode 25 is formed so that holes are collected in the pixel electrode 1b. A bias voltage is applied so that it becomes a positive electrode.

Switching thin film transistor (TF)
T) 1d has a polarity depending on the type of the X-ray photosensitive film 1a. That is, when the mobility of holes is higher than the mobility of electrons in the X-ray photosensitive film 1a, a p-channel TFT is used as the switching thin film transistor 1d. On the other hand, when the electron mobility is higher than the hole mobility in the X-ray photosensitive film 1a, an n-channel TFT is used as the switching thin film transistor 1d. In this embodiment, since the X-ray photosensitive film 1a in which the hole mobility is higher than the electron mobility is used, the switching thin film transistor (TFT) 1d is a p-channel T.
It is FT.

Further, the switching thin film transistor 1
d is a polycrystalline SiTFT (hereinafter referred to as "p-SiTFT"). The reason why the p-Si TFT is used in this way is, for example, as follows.

That is, in order to drive a high-definition, multi-pixel X-ray flat panel detector, a TFT having a high switching speed is required, but a conventional amorphous SiTFT (hereinafter referred to as "a-Si").
"TFT". In), the electron mobility is low, so that it cannot be driven sufficiently. Therefore, conventionally, a p-Si TF having high mobility is used as a TFT having a high switching speed.
T is used. The electron mobility and hole mobility of p-Si are about two orders of magnitude higher than that of a-Si. Specifically, the electron mobility of p-Si is 100 to 4
00, and the hole mobility of p-Si is 50 to 200.

Although it is possible to use single crystal Si, it is difficult to form a large-area TFT array required for an X-ray detector because the size of the single crystal Si substrate is small. . On the other hand, since p-Si can be formed on a glass substrate or the like, a large area TFT array can be formed.

However, the inventors have found that the p of n-ch is
In the -SiTFT, it has been found that the rise of the switch characteristics is greatly deteriorated by X-ray irradiation as shown in FIG. The deterioration of the rising of this switch characteristic is caused by a-Si.
It is not found in TFT and is a particularly remarkable problem in p-Si TFT. Therefore, due to this deterioration, n-ch p-Si
We have found that TFTs are not always suitable for X-ray flat panel detectors. Further, it is considered necessary to drive with a large drain voltage Vd in order to act as a protection diode.

Therefore, as a result of earnest research, the inventors have found that p
It has been found that the -ch p-Si TFT has a large drain voltage Vd resistance and a large X-ray resistance, and thus is suitable for the switching thin film transistor 1d. This pc
The remarkable effect of using the h-type p-Si TFT will be described in detail later. Conventionally, p-SiTFT has been used for liquid crystal display (TFT-LCD), but LC
In D, X-ray resistance is not required, so n-ch with high mobility
The p-Si TFT has been used conventionally. It was discovered for the first time that p-ch TFTs are superior to X-ray irradiation.

According to this structure, by applying a positive voltage to the upper electrode 25, a bias voltage that collects holes in the pixel electrode 1b can be applied to the X-ray photosensitive film 1a. By this bias voltage, the X-ray photosensitive film 1a
In, the holes generated according to the incident amount of X-rays can be stored in the storage capacitor 1c as signal charges. Then, by turning on the switching TFT 1d which is a p-ch p-Si TFT via the scanning line 3, the accumulated signal charges can be read out to the signal line 4 at high speed and with a high SN ratio. More specifically, the X-ray flat panel detector operates as follows.

FIG. 5 is a diagram for explaining the operation of the X-ray flat panel detector according to this embodiment. In FIG. 5, a bias voltage is applied to the X-ray photosensitive film 1a by applying a positive voltage of 10 kV from the upper electrode 25. Then, the switching TFT 1d is driven as shown in FIG. That is, for example, 10V is applied in advance when the gate is off, and -25V is applied as a gate pulse to turn on the switching TFT. It should be noted that, when performing imaging, X-ray irradiation is stopped when the gate pulse is applied. Further, when performing continuous fluoroscopy, a gate pulse is appropriately applied during the X-ray irradiation, and a signal charge reading operation is performed.

By doing this, a very strong X
When the line is irradiated and the pixel potential becomes very large and becomes a voltage equal to or higher than the sum of the off voltage of the gate pulse and the threshold value of the switching TFT, the switching TFT is turned on, and the pixel charge (storage capacitor Excess charge) flows out to the signal line.

Further, since the pixel potential does not exceed the sum of the off voltage of the gate pulse and the threshold value of the switching TFT, the high voltage does not cause dielectric breakdown of the gate insulating film of the switching TFT. Therefore, the switching TFT can be protected from high voltage. Figure 6
The original TFT characteristics of the p-channel TFT and the diode characteristics when 10 V is applied when the gate is off are shown in FIG. In the diode characteristics, the horizontal axis represents the pixel electrode potential, not the gate potential.

That is, according to the X-ray flat panel detector of the present embodiment, since the switching TFT 1d can be provided with the function of the protection circuit, it is possible to prevent excessive accumulation of charges in the additional storage capacitor 1c. It is not necessary to provide a protection circuit for doing so. Therefore, like the conventional X-ray flat panel detector, in the TFT array substrate on which the switching TFT, the X-ray photosensitive film, Cst, and the protective TFT are arranged, the TAB on which the bias line for the protective TFT is mounted is removed. There is no need to connect wiring for attachment. as a result,
Even when the pixel size is miniaturized, the wiring can be connected with a sufficiently narrow pitch. Furthermore, since a separate protection circuit is not required, a sufficient storage capacitor area can be secured even in a miniaturized pixel.

Further, the X-ray flat panel detector according to this embodiment uses the p-channel TFT made of p-Si as the switching TFT 1d. With this configuration, the following effects can be obtained.

First, in an X-ray flat panel detector that uses Se, which has a higher hole mobility as compared with electron mobility, as an X-ray photosensitive film, holes having a high mobility are detected as electric charges. The / N ratio can be improved. That is, in Se as the X-ray photosensitive film, if electrons having a low mobility are used as the charges accumulated in the storage capacitor, space charges are easily formed by the electrons having a low mobility captured in the defect region. The electrons are bent by the force and reach the adjacent pixels. Therefore, there is a possibility that burn-in will occur due to the accumulated space charge. On the other hand, in the present embodiment, since holes having high mobility and in which space charges are hard to be formed are accumulated in the accumulated charges, there is almost no deterioration in resolution and almost no burn-in is observed.

Secondly, the breakdown voltage of the switching TFT 1d against the breakdown due to the drain voltage can be made sufficiently high. According to the experiments by the inventors, the p-channel TFT manufactured by the method described in this embodiment can operate up to Vd of about 25 V even if the L length is 2 μm. On the other hand, the n-channel TF included in the conventional X-ray flat panel detector
At T, the drain breakdown voltage is about 1/2, which is 15V. The deterioration of the TFT characteristics due to the drain voltage is caused by the high-energy carriers accelerated by the drain electric field plunging into the gate insulating film and causing deterioration.

The X-ray flat panel detector according to this embodiment is p-
The ch p-Si TFT is used as the switching TFT 1d. Therefore, since holes have lower mobility than electrons and less energy at the drain, TF due to the drain voltage is increased.
The T characteristic deterioration can be reduced. Also, this TF
The defect charge that causes the deterioration of the T characteristic has a positive charge. Therefore, the holes as carriers of the switching TFT 1d travel a little away from the interface with the gate insulating film having the defect, and the influence from the defective charge can be reduced.

Thirdly, the X-ray flat panel detector according to the present embodiment uses a p-channel TFT as the switching TFT 1d.
Has high X-ray resistance. That is, generally, in the switching TFT used in the X-ray flat panel detector, a defect is generated by the irradiation of the X-ray, and the characteristic thereof is deteriorated. Due to the deterioration of this characteristic, the conventional X-ray flat panel detector may not operate normally. However, we will see that this degradation is n-ch p-S, as described below.
The iTFT is large enough to be difficult to operate as a flat panel detector, but the p-ch p-Si TFT has a T
Degradation of FT Vth and S-factor is p-ch p-S
It was found that it can be used because it is smaller than iTFT. This is the result of single-crystal Si MOS transistors, eg L. K. Wang "X-ray Lithogr
aphy Induced Radiation Da
image in CMOS and Bipolar
Devices "(Journal of Electr
onic Materials, vol. 21, N
o. 7, 1992) As you can see from Table 1, X
Deterioration due to the line irradiation, that is, the fluctuation of Vth and the fluctuation of the characteristic slope S-factor in the switch region are caused by the p-channel SiM.
It is considered that the OS transistor has a similar effect to that of the n-ch SiMOS transistor, but the polycrystalline Si is more remarkable.

Fourthly, the off-leakage current can be made small, and the minute charge generated at a low X-ray dose can be converted to a high S / S.
It can be detected by the N ratio. FIG. 7 shows a p-channel TFT 1 made of p-Si manufactured according to this embodiment.
It is the figure which showed the off leak current of d. As shown in the figure, when the switching TFT 1d has an LDD structure, the off leak current can be further reduced. The contents will be described in detail in the second embodiment.

FIG. 8 shows the p-channel T in this embodiment.
It is a figure showing the characteristic before and behind X-ray irradiation of FT. ◇ in the figure
The mark shows the characteristics before irradiation and the mark □ shows the characteristics after irradiation. The threshold value Vth of the TFT after the X-ray irradiation is compared with that before the X-ray irradiation.
Changes and the slope of the subthreshold becomes gentle.
The deterioration due to this X-ray irradiation is smaller in the p-ch p-Si TFT than in the n-ch p-Si TFT. Therefore,
A larger Vd is required to maintain the current drive capability. Although the TFT characteristics are deteriorated by the increase of the Vd voltage,
As described above, since the p-channel TFT has higher Vd withstand voltage and X-ray resistance than the n-channel TFT, it is possible to drive even with a larger Vd voltage. As a result, the signal charge that can be stored in the storage capacitor can be increased, and thus a signal can be detected with a high S / N ratio without being saturated even with a stronger X-ray.

(Second Embodiment) FIG. 9 shows a second embodiment of the present invention.
FIG. 3 is a plan view showing a one-pixel configuration of the X-ray flat panel detector according to the embodiment of FIG. In addition, FIG. 10 shows one of the X-ray flat panel detectors.
FIG. 11 is a cross-sectional view showing a pixel configuration (a cross section taken along 6B-6B in FIG. 9). The same parts as those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

The difference between the second embodiment and the first embodiment is that the switching TFT is LDD (Lightly Doped).
Drain) structure. In the manufacturing process of the present X-ray flat panel detector, until the undercoat insulating film 11, the p-Si film 12, the gate SiO ₂ film 13, and the gate electrode 14 are formed on the glass substrate 10, the first embodiment described above is used. Is the same as.

Next, the gate electrode or the resist is masked
As a result of ion implantation, B is 1 × 10¹¹cm^-2From 5
× 10¹⁴cm^-2, Preferably 3 × 10¹²cm^-2From 5x
10 ¹³cm^-2, 2 × 10 in this embodiment¹³cm^-2Dope
Then p of LDD^-Regions 35-1 and 35-2 are formed.
This is almost 1 × 10¹⁷cm^-3From 1 × 10²⁰cm^-3No
It corresponds to the pure substance concentration. LDD length is 0.5-5 μm, preferred
Specifically, 1 μm to 4 μm is selected. In this embodiment, 2
The LDD length was μm. Also, W / L = 10/5 μm
did.

Then, by ion implantation using the resist as a mask, B is 1 × 10 ^{14 to} 5 × 10 ¹⁶ cm ^-2 , preferably 1 × 10 ¹⁵ cm ^-2 to 1 × 10 ¹⁶ cm ^-2 . Then, high-concentration doping of 3 × 10 ¹⁵ cm ⁻² is performed to form p ⁺ regions 15-1 and 15-2 of the source / drain electrodes.

After that, as in the first embodiment, after forming the SiO ₂ film 16 of the interlayer insulating film, holes are formed in the source / drain contact portions and the signal line 17-1 is formed by Mo / Al / Mo. Cs line 17-2 is formed. Further, after forming a passivation SiNx film and a protective film 18 made of an acrylic resin, a contact portion is formed and the IT
A pixel electrode 19 made of O is formed. Then, the X-ray photosensitive film 1a is formed, and the electrode 25 is formed on the uppermost part.

The off-leakage current of the p-channel TFT made of p-Si thus manufactured is shown in FIG.
Compared with the case without D. The off current can be reduced by forming the LDD, as compared with the case without the LDD. The off current of the pixel driving TFT of the X-ray detector needs to be 1 × 10 ⁻¹² A or less.
By forming LDD, the off current is reduced to 3 × 10 ^-14
It can be made sufficiently small as A or less. TFT for liquid crystal
In order to handle a signal larger than that of the X-ray detector, the off current can be used at about 1 × 10 −10 A, so p−
The LDD structure of the chp-SiTFT is not used, and the structure is particularly effective for the X-ray flat panel detector.

When Se is used as the X-ray photosensitive film,
Se acts as a photodiode having a particularly high resistance and a very small leak current. Therefore, the switching TFT
By reducing the leak current at the off time, a weak signal due to a weak X-ray can be handled, and a highly sensitive X-ray detector can be realized. According to the research conducted by the inventors, a p-ch with LDD in a p-Si TFT is used.
It was found that the p-Si TFT of 1) can reduce the current at the most off time. Therefore, if Se having an extremely small dark current characteristic is used as an X-ray photosensitive film and a p-ch p-SiTFT is used as a switching element, an X-ray flat panel detector having higher sensitivity than the conventional one can be obtained. Can be realized.

The p-channel TFT is an n-channel T
Since the drain voltage resistance is higher than that of the FT, it is possible to handle a larger X-ray signal, thereby expanding the dynamic range.

Further, the TFT characteristics of the present X-ray flat panel detector before and after X-ray irradiation are similar to those in the case of FIG. 8 described in the first embodiment, after the X-ray irradiation, Vth changes and the subthreshold is changed. The inclination of becomes gentle. However, p channel T
By using the FT, it is possible to drive even with a larger Vd voltage, and it is possible to increase the signal charge that can be stored in the storage capacitor.
Therefore, a signal can be detected without being saturated even with a stronger X-ray, and the dynamic range can be expanded. Further, since the sub-threshold is less deteriorated by X-ray irradiation, the amount of signal charges that can be processed by the signal can be increased.

(Third Embodiment) FIG. 11 is a circuit configuration diagram showing a driver circuit in an X-ray flat panel detector according to a third embodiment of the present invention. Also. FIG. 12 is a sectional view of the driver circuit. In addition, in FIG.
The same parts as those of the above are denoted by the same reference numerals, and detailed description thereof will be omitted.

The third embodiment is a switching TFT.
Is a driver circuit provided in a peripheral circuit for driving the driver circuit. This driver circuit is configured by using a p-channel TFT and an n-channel TFT. The manufacturing of each TFT is
This is performed at the same time as the manufacturing of the TFT in the imaging area.

Similar to the imaging area, SiNx (50 nm) as the undercoat insulating film 11 is formed on the glass substrate 10.
/ SiO ₂ (100 nm) is formed and a-Si is formed on it.
A film is formed with a film thickness of 50 nm. Then, a-
The Si film is polycrystallized to form a 50 nm p-Si film. Then, the p-Si film 12 is etched to form islands 12-3 and 12-4 of the peripheral circuit together with the island 12-1 of the transistor region and the island 12-2 of the capacitor region. Then, a gate SiO ₂ film 13 is formed to a thickness of 150 nm by PCVD or thermal CVD.

Next, the MoW gate 14 is set to 300 nm.
To the thickness of. Here, together with the gate electrode 14-1 in the transistor region and the gate electrode 14-2 in the capacitor region in the imaging region, the CMOS in the peripheral circuit is used.
The gate electrodes 14-3 and 14-4 of the transistor are formed.

[0058] Then, similarly to the imaging area, the B gate electrode or a resist as a mask to 2 × 10 ¹³ cm ^-2 doped LDD of to form p ^- regions 35-4,35-5.
This corresponds to an impurity concentration of approximately 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ . Here, the LDD length is, for example, 2 μm, and W / L = 10/5 μm.
Then, using the resist as a mask, B is 3 × 10 ¹⁵ cm ^-2
P ⁺ region 1 of the source / drain electrodes after being heavily doped
5-4 and 15-5 are formed.

Next, apart from the imaging region, P is 1 × by ion implantation using the gate electrode or the resist as a mask.
10 ¹¹ cm ^-2 to 5 × 10 ¹⁴ cm ^-2 , preferably 3 × 1
0 ¹² cm ⁻² to 5 × 10 ¹⁴ cm ⁻² , 2 × in this embodiment
N ^- region 55-4,5 of LDD doped with 10 ¹³ cm ^-2
5-5 is formed. This corresponds to an impurity concentration of approximately 3 × 10 ¹⁶ cm ⁻³ to 2 × 10 ²¹ cm ⁻³ . The LDD length is selected to be 0.5 to 5 μm, preferably 1 to 4 μm. In this embodiment, the LDD length is, for example, 2 μm, and W
/ L = 10/5 μm. Then, using the resist as a mask, P is set to 1 10 ¹⁴ cm ^{−2 to} 5 × 10 ¹⁶ cm ⁻² , preferably 3 × 10 ¹⁴ cm ^{−3 to} 5 × 10 ¹⁵ cm ⁻² , and 2 × 10 in the present embodiment. High-concentration doping of ¹⁵ cm ⁻² is performed to form n ⁺ regions 45-4 and 45-5 of the source / drain electrodes.

Then, similarly to the image pickup region, an SiO ₂ film 16 as an interlayer insulating film is formed by PCVD to a thickness of 500 nm. Next, a hole is opened in the source / drain contact part, and Mo /
The signal line 17-1 and the Cs line 17 described above are made of Al / Mo.
-2 and form gate electrodes 14-4 and 14-5
Wirings 54-1 and 54-2 connected to are formed. After that, a SiNx film for passivation is formed by PCVD, and an acrylic photosensitive resin is further coated in a thickness of 2 to 5 μm, preferably 3 μm to form a protective film 18. Protective film 18
Since is a photosensitive resin, a contact hole can be formed only by exposure and development.

By such a process, the pixel circuit has p
With channel TFT, the peripheral drive circuit is p-channel TFT
And an n-channel TFT CMOS.

The X-ray flat panel detector according to this embodiment can improve the circuit characteristics of the peripheral circuits and reduce the power consumption. In addition, p-S manufactured according to this embodiment
By using the driving circuit of the CMOS structure of the TFT made of i, the signal charges can be sufficiently read out even in a short address time, and thus pixels with a fine pitch can be driven. This configuration has a pixel size of 6
It can be applied to an X-ray flat panel detector for 0 μm square breast examination. It is difficult to manufacture such an X-ray flat panel detector having such fine pixels because the conventional technique could not be mounted with a pitch of 60 μm.

The present invention is not limited to the above embodiments. The high-sensitivity X-ray photosensitive film is not limited to Se as described above, but may be any polycrystalline or single-crystal high-efficiency X-ray photosensitive material such as PbTe, HgTe, ZnS, or a mixed crystal thereof. The film thickness of the high sensitivity X-ray photosensitive film may be a film thickness capable of sufficiently absorbing X-rays. Further, the film thickness of the high resistance semiconductor film may be selected so that the photo carriers (electrons or holes) can travel through the high resistance film in about 1/10 of the address time.

The substrate is not limited to the glass substrate, and any substrate can be used as long as it can form a TFT. Since the X-ray photosensitive film used in the embodiment can be formed by coating at a low temperature, a plastic or the like having low heat resistance may be used as the substrate. In this case, the entire X-ray flat panel detector can be made to have plasticity. Further, the structure of the TFT may be on the gate or below the gate.

As the protective film, inorganic SiN _x and SiO ₂ , and organic polyimides (ε = about 3.3,
Withstand voltage of about 300 V / mm) and benzocyclobutene (ε =
Approximately 2.7, withstand voltage of approximately 400 V / mm), acrylic photosensitive resin HRC (ε = approximately 3.2) manufactured by JSR Corporation, black resist, etc. may be used, and these may be laminated as necessary. . As the protective film, a fluorine-based resin is also effective because it has a small relative dielectric constant (ε = about 2.1). The protective film may not be photosensitive, but a photosensitive material is effective because patterning is easier.

The present invention has been described above based on the embodiments. However, within the scope of the idea of the present invention, those skilled in the art can come up with various modifications and modifications, and the modifications and modifications. It is understood that the examples also belong to the scope of the present invention. For example, in the above embodiment, the incident X
The X-ray flat panel detector of the direct conversion system for converting the rays into electron-hole pairs by the photoelectric conversion film has been described as an example. However,
The technical idea of the present invention is that even with an indirect conversion type X-ray flat detector in which incident X-rays are once converted into light by a phosphor and the light is converted into electron-hole pairs by a photoelectric conversion film,
Applicable.

Further, the respective embodiments may be combined as much as possible, and in that case, combined effects can be obtained. Further, the embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problem described in the section of the problem to be solved by the invention can be solved, and the effect described in the section of the effect of the invention can be solved. When at least one of the above is obtained, the configuration in which this constituent element is deleted can be extracted as the invention.

[0068]

As described above, according to the present invention, it is possible to realize an X-ray flat panel detector which prevents the pixel circuit from becoming complicated due to the protection action against a high voltage and can obtain a good image even if the pixel is miniaturized. it can.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic configuration of an X-ray flat panel detector according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a pixel 1.

3 is a cross-sectional view showing the structure of a pixel 1 (3 in FIG. 2).
It is a section along B-3B).

FIG. 4 is a schematic diagram of n used in a conventional X-ray flat panel detector.
FIG. 8 is a diagram showing a change in the rising edge of the switch characteristics of a −ch p-SiTFT before and after X-ray irradiation.

FIG. 5 is a diagram for explaining the operation of the X-ray flat panel detector according to the first embodiment.

FIG. 6 shows the original T of a p-channel p-Si TFT.
FIG. 10 is a diagram showing FT characteristics and characteristics of a conventional diode when 10 V is applied when the gate is off.

FIG. 7 is a diagram showing an off-leakage current of a p-channel TFT 1d made of p-Si manufactured as in the first embodiment.

FIG. 8 is a p-channel T in the first embodiment.
It is a figure showing the characteristic before and behind X-ray irradiation of FT.

FIG. 9 is a plan view showing a one-pixel configuration of an X-ray flat panel detector according to a second embodiment of the present invention.

FIG. 10 is a cross-sectional view (cross-section taken along line 6B-6B in FIG. 9) showing a one-pixel configuration of the X-ray flat panel detector according to the second embodiment.

FIG. 11 is a circuit configuration diagram showing a driver circuit in an X-ray flat panel detector according to a third embodiment of the present invention.

12 is a cross-sectional view of the driver circuit shown in FIG.

FIG. 13 shows a circuit configuration of one pixel of a conventional X-ray flat panel detector.

[Explanation of symbols]

1a ... X-ray photosensitive film 1b, 19 ... Pixel electrode 1c ... Storage capacitor 1d ... Switching thin film transistor 2 ... Imaging area 3 ... Scan line 4, 17-1 ... Signal line 5 ... Gate driver 10 ... Glass substrate 11 ... Undercoat insulation Film 12 ... p-Si film 13 ... gate SiO ₂ film 14 ... gate electrode 15-2 ... source 15-1 ... drain 15-3 ... p ⁺ region 17 ... Mo / Al / Mo film 18 ... protective film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/32 H01L 27/14 K (72) Inventor Kohei Suzuki 1 Komukai Toshiba Town, Kawasaki City, Kanagawa Prefecture address Co., Ltd., Toshiba research and development Center in the F-term (reference) 2G088 EE01 FF02 GG21 JJ05 JJ09 JJ31 JJ33 JJ35 JJ37 KK32 LL12 LL18 4M118 AA08 AB01 BA05 CA05 CA32 CB05 CB08 CB14 EA05 FB09 FB13 FB16 GA10 5C024 AX11 CX37 CY47 5F088 AA03 AB01 BA20 BB03 BB07 CB05 CB06 CB08 CB12 DA01 DA20 EA04 EA08 EA16 GA02 KA03 KA08 LA08

Claims (28)

[Claims] 1. An X-ray photosensitive film that is exposed to incident X-rays to generate signal charges, a plurality of pixel electrodes that are two-dimensionally arranged in contact with the X-ray photosensitive film, and Bias voltage applying means for applying a bias voltage to the X-ray photosensitive film so that one of holes and electrons as generated signal charges, which has a higher mobility, is collected by the plurality of pixel electrodes, and the pixel. A plurality of capacitors provided for each electrode for accumulating electric charges generated by the X-ray photosensitive film; a plurality of switching thin film transistors provided for each pixel electrode for reading out electric charges accumulated by the capacitors; A plurality of scanning lines for supplying a control signal for controlling the opening and closing of the thin film transistor for switching, and the switching line connected to the plurality of switching thin film transistors. X-ray flat panel detector characterized by comprising: a plurality of signal lines for reading out the charge when the thin film transistor is closed. 2. The X-ray flat panel detector according to claim 1, wherein the plurality of switching thin film transistors have an LDD structure. 3. The plurality of switching thin film transistors are characterized in that, of holes and electrons as signal charges generated in the X-ray photosensitive film, one having a higher mobility is used as a carrier. The X-ray flat panel detector described in 2. . 4. The X-ray photosensitive film is made of a material having hole mobility higher than electron mobility, and the plurality of switching thin film transistors are single crystal silicon or polycrystalline silicon p-channel thin film transistors. The X-ray flat panel detector according to claim 3, characterized in that 5. The X-ray photosensitive film has a nip structure, and has the pixel electrode provided on the p side, and a common electrode as an anode provided on the n side. X-ray flat panel detector. 6. The X-ray photosensitive film is made of a material having electron mobility higher than hole mobility, and the plurality of switching thin film transistors are single-crystal silicon or polycrystalline silicon n-channel thin film transistors. The X-ray flat panel detector according to claim 3, characterized in that 7. The X-ray photosensitive film has a nip structure, and has the pixel electrode provided on the n side, and a common electrode as a cathode provided on the p side. X-ray flat panel detector. 8. The X-ray photosensitive film is made of Se, PbI ₂ , Pb.
Te, HgTe, HgI ₂ , ZnS, ZnTe, Ga
P, AlSb, CdZnTe, CdTe, CdSe, C
4. The X-ray flat panel detector according to claim 1, wherein at least one of dS is an amorphous semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a mixed crystal semiconductor. 9. An X-ray photosensitive film that is exposed to incident X-rays to generate signal charges, a plurality of pixel electrodes that are two-dimensionally arranged in contact with the X-ray photosensitive film, and the X-ray photosensitive film. Bias voltage applying means for applying a bias voltage to the X-ray photosensitive film so that one of holes and electrons as generated signal charges, which has a higher mobility, is collected by the plurality of pixel electrodes, and the pixel. A plurality of capacitors provided for each electrode for accumulating charges generated by the X-ray photosensitive film; and holes and electrons as signal charges generated in the X-ray photosensitive film provided for each pixel electrode, A plurality of switching thin film transistors for reading out charges accumulated in the capacitor, with a higher mobility as a carrier, and a control signal for controlling opening / closing of the plurality of switching thin film transistors. X-rays comprising: a plurality of scanning lines for supplying a plurality of scanning lines; and a plurality of signal lines that are connected to the plurality of switching thin film transistors and read out the charges when the switching thin film transistors are closed. Planar detector. 10. The plurality of switching thin film transistors have an LDD structure.
X-ray flat panel detector described. 11. The X-ray photosensitive film is made of a material having hole mobility higher than electron mobility, and the plurality of switching thin film transistors are single crystal silicon or polycrystalline silicon p-channel thin film transistors. The X-ray flat panel detector according to claim 9 or 10, characterized in that. 12. The X-ray photosensitive film has a nip structure, and has the pixel electrode provided on the p side, and a common electrode as an anode provided on the n side. X-ray flat panel detector. 13. The X-ray photosensitive film is made of a material having electron mobility higher than hole mobility, and the plurality of switching thin film transistors are single-crystal silicon or polycrystalline silicon n-channel thin film transistors. The X-ray flat panel detector according to claim 9 or 10, characterized in that. 14. The X-ray photosensitive film has a pin structure, and has the pixel electrode provided on the n side and a common electrode as a cathode provided on the p side. X-ray flat panel detector. 15. The X-ray photosensitive film is made of Se, PbI ₂ , P.
bTe, HgTe, HgI ₂ , ZnS, ZnTe, Ga
P, AlSb, CdZnTe, CdTe, CdSe, C
The X-ray flat panel detector according to claim 9 or 10, wherein at least one of dS is an amorphous semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a mixed crystal semiconductor. 16. An X-ray photosensitive film which is made of a material having a hole mobility higher than an electron mobility and which is exposed to an incident X-ray to generate a signal charge, and a two-dimensional film in contact with the X-ray photosensitive film. And a bias for applying a bias voltage to the X-ray photosensitive film so that holes as signal charges generated in the X-ray photosensitive film are collected in the plurality of pixel electrodes. Voltage applying means, a plurality of capacitors provided for each of the pixel electrodes and accumulating charges generated by the X-ray photosensitive film, provided for each of the pixel electrodes on an insulating substrate, and having an island shape on the insulating substrate. A plurality of p-channel thin film transistors having a provided polycrystalline silicon film for reading out signal charges accumulated in the capacitor, and a control signal for controlling opening / closing of the plurality of p-channel thin film transistors are supplied. X-ray plane, comprising: a plurality of scanning lines; and a plurality of signal lines that are connected to the plurality of p-channel thin film transistors and read out the signal charges when the p-channel thin film transistors are closed. Detector. 17. The X-ray flat panel detector according to claim 16, wherein each of the plurality of p-channel thin film transistors has an LDD structure. 18. The X-ray photosensitive film is made of Se, AlSb, G
18. The X-ray flat panel detector according to claim 16, wherein at least one of aP is an amorphous semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a mixed crystal semiconductor. 19. An X-ray photosensitive film, a p-channel thin film transistor, and an island-shaped polycrystalline silicon film provided in a peripheral region of an imaging region where a storage capacitor section is arranged. The drive circuit further comprises a plurality of drive circuits for driving.
19. The X-ray flat panel detector according to claim 18. 20. An X-ray photosensitive film, which is made of a material having electron mobility higher than hole mobility, is exposed to incident X-rays to generate electrons and holes, and is in contact with the X-ray photosensitive film. A plurality of two-dimensionally arranged pixel electrodes, a plurality of capacitors that are provided for each of the pixel electrodes and store electrons generated by the X-ray photosensitive film, and a plurality of capacitors that are provided for each of the pixel electrodes and that store the capacitors. A plurality of n-channel thin film transistors that read out electrons, a plurality of scanning lines that supply a control signal for controlling the opening and closing of the plurality of n-channel thin film transistors, and a plurality of n-channel thin film transistors connected to the n-channel thin film transistors. An X-ray flat panel detector comprising: a plurality of signal lines for reading the electrons when 21. The X-ray flat panel detector according to claim 20, wherein each of the plurality of n-channel thin film transistors has an LDD structure. 22. The X-ray photosensitive film has a pin structure, and has the pixel electrode provided on the n side and a common electrode as a cathode provided on the p side. 21. The X-ray flat panel detector described in 21. 23. The X-ray photosensitive film is made of PbI ₂ , CdS.
e, CdTe, CdS, ZnTe, ZnTe, CdZn
23. The X-ray plane according to claim 20, wherein at least one of Te and HgI ₂ is an amorphous semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a mixed crystal semiconductor. Detector. 24. An X-ray photosensitive film which is exposed to incident X-rays to generate a signal charge; a plurality of pixel electrodes which are two-dimensionally arranged in contact with the X-ray photosensitive film; Bias voltage applying means for applying a bias voltage, a plurality of capacitors provided for each pixel electrode for accumulating charges generated by the X-ray photosensitive film, and charges provided for each pixel electrode and accumulated by the capacitor A plurality of polycrystalline silicon p-channel thin film transistors for reading out, a plurality of scanning lines supplying a control signal for controlling the opening and closing of the plurality of switching thin film transistors, and connected to the plurality of switching thin film transistors, A plurality of signal lines for reading the charges when the switching thin film transistor is closed; X-ray flat panel detector. 25. The plurality of switching thin film transistors have an LDD structure.
The X-ray flat panel detector according to item 4. 26. The X-ray photosensitive film is made of PbI ₂ , CdS.
e, CdTe, CdS, ZnTe, ZnTe, CdZn
26. The X-ray flat panel detector according to claim 24, wherein at least one of Te and HgI ₂ is an amorphous semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a mixed crystal semiconductor. 27. The switching thin-film transistor according to claim 24, wherein one of holes and electrons as a signal charge generated in the X-ray photosensitive film has a higher mobility as a carrier. 25. The X-ray flat panel detector described in 25. 28. The X-ray photosensitive film is made of Se, AlSb, G
26. The X-ray flat panel detector according to claim 24, wherein at least one of aP is an amorphous semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a mixed crystal semiconductor.