KR100577794B1 - Digital X-ray detector - Google Patents

Abstract

The present invention discloses a digital X-ray detector. The disclosed digital X-ray detector includes a thin film transistor and a common line formed on a transparent insulating substrate, a first protective film coated on the entire surface of the substrate to cover the thin film transistor and the common line, and a thin film transistor on the first protective film. A first transparent electrode formed to contact the common line, and a second protective layer formed to cover the first transparent electrode; A second transparent electrode formed on the second passivation layer to be in contact with the first transparent electrode portion in contact with the thin film transistor, and a protrusion disposed on the thin film transistor on the second passivation layer with the same material as the second transparent electrode. An inner guard line formed to be parallel to at least one of the gate line and the data line of the thin film transistor, and an inner guard line on the second passivation layer to surround the outside of the pixel region with the same material as the second transparent electrode. And an outer guard line formed to be connected to both one end and the other end of the. According to the present invention, an additional guard line is provided to remove the charge on the thin film transistor in advance, thereby effectively preventing an increase in leakage current generated when reading the charge stored in the storage capacitor.

X-ray detector, inner guard line, outer guard line

Description

Digital X-ray Detector

1 is a schematic diagram for explaining a conventional digital x-ray detector.

2A and 2B are plan and cross-sectional views for explaining another conventional digital X-ray detector.

3 is a view showing a change in thin film transistor characteristics according to the voltage change to the charge collecting electrode in the conventional digital x-ray detector.

4A and 4B are a plan view and a sectional view for explaining another conventional digital x-ray detector.

5 is a view showing a characteristic change of the thin film transistor when the common signal is applied to the upper portion of the thin film transistor.

6A and 6B are a plan view and a cross-sectional view of a digital x-ray detector according to an embodiment of the present invention.

7 is a plan view showing an inner guard line and an outer guard line of the digital x-ray detector according to the present invention.

8 is a cross-sectional view of a digital x-ray detector according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

20: glass substrate 21: gate line

22 gate insulating film 23 active layer

24: data line 24a: source electrode

24b: drain electrode 25: common line

26: first protective film 27: the first transparent electrode

28: second protective film 29: second transparent electrode

V1, V2: Via hole 60: Internal guard line

62: external guard line 63: guard line signal extraction line

64: gate pad 66: data pad

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital x-ray detector, and more particularly, to a digital x-ray detector for effectively removing a charge generated on a thin film transistor.

The X-ray inspection method currently used for medical imaging uses X-ray detection film, and film development time has to elapse in order to know the result, and many efforts are made to store / manage these films. This is necessary. Accordingly, in order to compensate for the above disadvantages, a digital x-ray detector (DXD) using a thin film transistor has been developed, and the digital x-ray detector makes it possible to diagnose a result in real time after x-ray imaging.

1 is a view for explaining the configuration and operation of the conventional digital X-ray detector, as shown, the conventional digital X-ray detector is a thin film transistor (TFT), a storage capacitor (Cap) and a charge collecting electrode (Chage) on the lower substrate Collecting Electrode (10) is formed, and a photoconductor (10) and a conductive electrode (11) are sequentially formed on the charge collecting electrode (9).

 According to the conventional digital x-ray detector, the photoconductive film 10 located above the thin film transistor (TFT) converts the x-ray into an electrical signal in proportion to the signal intensity. That is, when the X-rays are irradiated, electron-hole pairs are formed in the photoconductive film 10, which is formed by the charge collection electrode (TFT) above the thin film transistor (TFT) by a voltage of several kV applied to the conductive electrode 11 located thereon. 9) in the form of charge, and then stored in the storage capacitor (Cap), the stored charge is read out when the thin film transistor (TFT) is turned on (Turn-On) by an external signal The circuit exits to show the X-ray image. At this time, the charge remaining in the storage capacitor (Cap) without exiting the outer arc is removed through the ground line.

Therefore, such a digital X-ray detector can check the result immediately after the X-ray photographing using a thin film transistor (TFT) as a switching element, and it is easy to store the result as a digital signal, so that the result can be easily stored and semi-permanently preserved. can do.

However, in the conventional digital X-ray detector, charges generated in the photoconductive film are collected not only on the charge collecting electrode but also on the passivation layer protecting the channel region of the thin film transistor, so that the charge is induced to the channel region so that the thin film transistor is turned off. Even in the state, a large leakage current is generated.

Therefore, in order to prevent this, a so-called mushroom (US Patent No. 5,498, 880) structure has been proposed in which a conductive electrode extends to the upper portion of the thin film transistor so that electric charges existing in the upper portion of the thin film transistor can escape to an external circuit. The structure is as shown in Figs. 2A and 2B.

2A and 2B, reference numeral 20 denotes a glass substrate, 21 gate line, 22 gate insulating film, 23 active layer, 24 data line, 24a source electrode, 24b drain electrode, and 25 common line. line), 26 is a first protective film, 27 is a first transparent electrode, 28 is a second protective film, 29 is a second transparent electrode corresponding to a charge collection electrode, and V1 and V2 represent first and second via holes, respectively. .

However, in the mushroom structure, as the charge generated by the X-rays is collected at the charge collecting electrode, that is, the second transparent electrode 29, the potential of the storage capacitor is increased, and thus, the thin film transistor TFT and the second transparent electrode ( Between the parasitic capacitors. Accordingly, when the charge is induced in the channel region of the thin film transistor TFT by the parasitic capacitor, the leakage current increases when the positive charge is collected at the charge collecting electrode. On the contrary, the negative charge is charged to the charge collecting electrode. Gathers, the on-current decreases.

In fact, the voltage applied to the upper portion of the thin film transistor (TFT) by the charge collecting electrode charge during X-ray driving is approximately ± 10V, and FIG. 3 is a graph showing data measuring the influence of TFT characteristics.

Therefore, in order to prevent defects caused by such parasitic capacitors, that is, to reduce parasitic capacitor capacity, a structure in which an organic dielectric film material (BCB, acrylic, polyimide) having a low dielectric constant is formed as a protective film of 2 μm or more is proposed in Korea. It was proposed as a patent application 10-1999-0011516.

However, although not shown and described, in this structure, a process for forming an organic insulating film needs to be added, and thus there is a problem of investment in production equipment, and a problem of increasing a defective rate due to a high step.

In addition, as another method for solving the above problem, a ground line, that is, a first transparent electrode connected to a common line is disposed on the upper portion of the thin film transistor so that the ground state of the thin film transistor is always maintained in the ground state. A ground shilding structure has been proposed in Korean Patent Application No. 10-2001-0042124, the structure of which is as shown in FIGS. 4A and 4B.

In Figs. 4A and 4B, the same parts as Figs. 2A and 2B are denoted by the same reference numerals, and 31 denotes an etch stopper.

However, according to such a structure, defects caused by parasitic capacitors can be suppressed. However, when a signal is applied to the TFT, the TFT characteristics move to the right, as shown in FIG. 5. On current (Ion) decreases. According to the actual data, on-current reduction of about 33% occurs before and after the common signal is applied to the thin film transistor.

(Ion: 1.3V ⇒ 0.87㎶ for Vg = 20V, Vd = 10V, W / L = 13/11 thin film transistor)

Accordingly, the present invention has been made to solve the above problems, the digital x-ray to effectively remove the charges collected on the thin film transistor to prevent defects caused by parasitic capacitors, as well as to prevent changes in the characteristics of the thin film transistor. The purpose is to provide a detector.

In order to achieve the above object, the present invention, a thin film transistor and a common line formed on a transparent insulating substrate; A first passivation layer coated on an entire surface of the substrate to cover the thin film transistor and the common line; A first transparent electrode formed on the first passivation layer to be in contact with the thin film transistor and the common line; A second passivation layer formed to cover the first transparent electrode; A second transparent electrode formed on the second passivation layer to be in contact with the first transparent electrode portion in contact with the thin film transistor; An inner guard line formed on the second passivation layer in parallel with at least one of a gate line and a data line of the thin film transistor including a protrusion disposed on the thin film transistor with the same material as the second transparent electrode; And an outer guard line formed on the second passivation layer to surround the outside of the pixel region with the same material as the second transparent electrode and connected to both one end and the other end of the inner guard line.

In addition, the present invention, a thin film transistor and a common line formed on the transparent insulating substrate; A first passivation layer coated on an entire surface of the substrate to cover the thin film transistor and the common line; A first transparent electrode formed on the first passivation layer in contact with the thin film transistor and the common line; A second passivation layer formed to cover the first transparent electrode; A second transparent electrode formed on the second passivation layer to be in contact with the first transparent electrode portion in contact with the thin film transistor; Parallel to at least one of the gate line and the data line of the thin film transistor, including protrusions on the first protective layer and the second protective layer, the protrusions being made of the same material and being in contact with each other and disposed on the thin film transistor, respectively. An internal guard line of a dual structure formed to be disposed; And an outer guard line formed on the second passivation layer to surround the outside of the pixel region with the same material as the second transparent electrode and connected to both one end and the other end of the inner guard line.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 6A is a plan view of a digital X-ray detector according to the present invention, and FIG. 6B is a cross-sectional view taken along the line AA ′ of FIG. 6A. 2A and 2B are denoted by the same reference numerals.

As shown, the digital X-ray detector according to the present invention has a charge removing pattern, that is, an inner guard line 60 is further formed on the TFT, and as the inner guard line 60 is formed, The second transparent electrode 29 corresponding to the collecting electrode is not disposed on the thin film transistor TFT, wherein the inner guard line 60 is formed of the second transparent electrode corresponding to the charge collecting electrode. When formed together.

Here, the inner guard line 60 is formed to be parallel to the gate line 21 including a protrusion disposed on the thin film transistor TFT. In addition, as shown in FIG. 7, one end and the other end of the inner guard line 60 are connected to an outer guard line 62 formed to surround the outside of the display area for charge removal. In addition, the external guard line 62 is connected by the gate pad 64 and the guard line signal extraction line 63.

According to the digital x-ray detector of the present invention, the charge accumulated on the inner guard line 60 is removed together with the charge extraction on the outer guard line 62 before the thin film transistor (TFT) operation, and thus, the storage capacitor During operation of the thin film transistor (TFT) for reading out the charge stored in the element, which adversely affects the thin film transistor characteristic is removed.

In detail, the operation of the digital x-ray detector according to the present invention is as follows.

For example, when X-rays are irradiated through the human body, electron-hole pairs are formed in the photoconductive film, and the charges thus collected are collected at the charge collecting electrode by the high voltage.

In this state, first, before the charges stored in the storage capacitor are read out, the charges accumulated in the inner guard line formed in parallel with the thin film transistor and the gate line and the outer guard line outside the pixel region are extracted. Then, the thin film transistor is turned on by applying a signal to the gate line, and then a signal is applied to the data line to read the charge stored in the storage capacitor.

Accordingly, the digital x-ray detector of the present invention does not affect the back channel of the thin film transistor because the charge accumulated in the upper portion of the thin film transistor is already out. The charge generated by the X-rays can be read efficiently without deterioration.

Method of manufacturing a digital x-ray detector according to an embodiment of the present invention described above is as follows.

First, a gate line 21 including a gate electrode is formed on a glass substrate 20 that is a transparent insulating substrate, for example, a metal having good electrical conductivity, such as aluminum or an aluminum alloy, and then covers the gate line 21. A gate insulating film 22 made of SiNx, SiON, or the like is deposited on the entire surface of the substrate 20 including the substrate 20. Then, an undoped amorphous silicon film and a doped amorphous silicon film are sequentially deposited on the gate insulating film 22, and then etched to form an active layer 23.

Next, a metal film having excellent electrical conductivity is deposited on the entire surface of the substrate, and then etched to form a data line 24 including the source / drain electrodes 24a and 24b, and at the same time, the common line 25 is formed in the pixel region. Form. In this case, when the source / drain electrodes 24a and 24b are formed, the channel is etched by a predetermined thickness between the doped amorphous silicon film and the undoped amorphous silicon film between the source electrode 24a and the drain electrode 24b. At the same time, a thin film transistor (TFT) is formed.

Next, after applying the first passivation layer 26 on the entire surface of the substrate including the thin film transistor TFT, the first passivation layer 26 is etched to expose the common line 25 and the source electrode 24a, respectively. First via holes V1 are formed. Thereafter, a transparent metal film, for example, an ITO or IZO metal film, is deposited on the first passivation layer 26, and then etched to form the source electrode 24a and the common line 25 through the first via hole V1. ) Is formed to contact the first transparent electrode 27.

Next, after applying the second protective film 28 on the first protective film 26 to cover the first transparent electrode 27, the second protective film 28 is etched to contact the source electrode 24a. A second via hole V2 exposing the first transparent electrode part is formed. Thereafter, an ITO metal film is deposited on the second via hole V2 and the second passivation layer 28, and then etched to form a charge collection electrode contacting the first transparent electrode portion in contact with the source electrode 24a. The inner guard line 60 and the inner guard line disposed parallel to the gate line 21, including the second transparent electrode 29 corresponding to each other and a protrusion disposed on the TFT, The outer guard line 62 is formed to surround the outside of the pixel area while being connected to one end and the other end of the 60.

Here, the inner guard line 60 is simply formed above the thin film transistor (TFT) and formed to be parallel to the gate line 21. As another embodiment of the present invention, as shown in FIG. The first transparent electrode 27 and the second transparent electrode 29 may be connected to each other to form a double guard structure.

In addition, although the internal guard line 60 is formed to be parallel to the gate line 21, as another embodiment of the present invention, the internal guard line 60 may be formed to be parallel to the data line 24, and the gate line 21 may also be formed. And a pattern in the form parallel to all of the data lines 24.

In addition, the inner guard line 60 minimizes the overlapping degree with the gate line 21 or the data line 24 in consideration of an increase in line capacitance, and may be formed of a lattice or several lines.

Therefore, although the preferred embodiment of the present invention has been described above, it is clear that the present invention can use various changes, modifications, and equivalents, and that the above embodiments can be appropriately modified and applied in the same manner. Does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, the present invention further forms a charge removing pattern, that is, a guard line on the thin film transistor when the second transparent electrode corresponding to the charge collecting electrode is formed, and before the operation of the thin film transistor using the guard line. By allowing the charge accumulated on the thin film transistor to be extracted, the characteristics of the thin film transistor due to the parasitic capacitor between the thin film transistor and the charge collecting electrode, which are generated when reading data stored in the storage capacitor, can be prevented. In addition, the present invention can provide a digital x-ray detector that can efficiently read out the charge generated by the x-ray without increasing the leakage current and decreasing the on-current.

Claims (2)

A thin film transistor and a common line formed on the transparent insulating substrate; A first passivation layer coated on an entire surface of the substrate to cover the thin film transistor and the common line; A first transparent electrode formed on the first passivation layer to be in contact with the thin film transistor and the common line; A second passivation layer formed to cover the first transparent electrode; A second transparent electrode formed on the second passivation layer to be in contact with the first transparent electrode portion in contact with the thin film transistor; An inner guard line formed on the second passivation layer in parallel with at least one of a gate line and a data line of the thin film transistor including a protrusion disposed on the thin film transistor with the same material as the second transparent electrode; And And an outer guard line formed on the second passivation layer to surround the outside of the pixel region with the same material as the second transparent electrode and connected to both one end and the other end of the inner guard line. A thin film transistor and a common line formed on the transparent insulating substrate; A first passivation layer coated on an entire surface of the substrate to cover the thin film transistor and the common line; A first transparent electrode formed on the first passivation layer to be in contact with the thin film transistor and the common line; A second passivation layer formed to cover the first transparent electrode; A second transparent electrode formed on the second passivation layer to be in contact with the first transparent electrode portion in contact with the thin film transistor; Parallel to at least one of the gate line and the data line of the thin film transistor, including protrusions on the first protective layer and the second protective layer, the protrusions being made of the same material and being in contact with each other and disposed on the thin film transistor, respectively. An internal guard line of a dual structure formed to be disposed; And And an outer guard line formed on the second passivation layer to surround the outside of the pixel region with the same material as the second transparent electrode and connected to both one end and the other end of the inner guard line.

Images