Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2003-02-05
2004-10-26
Pham, Long (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S184000, C257S187000, C257S292000, C257S293000, C257S432000, C257S462000
Reexamination Certificate
active
06809357
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-029907, filed Feb. 6, 2002, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid-state imaging device of flat panel detection type in which photoelectric conversion pixels are arrayed in the shape of a matrix, and which is applied to, for example, an X-ray diagnosis apparatus for medical treatment.
2. Description of the Related Art
In recent years, in the field of medical treatment, the medical data of patients have been databased for the purpose of performing therapies promptly and accurately. Databasing has been required also for the image data of X-ray radiography, and the digitization of X-ray radiographic images has been desired. Since, however, the images are radiographed with a silver halide film in a conventional X-ray diagnosis apparatus for medical treatment, the digitization thereof needs to be implemented in such a way that, after the radiographed film has been developed, it is further scanned by a scanner or the like so as to convert the images into electric signals, followed by a digital process. Accordingly, labor and time are expended on the digitization of the images. Therefore, a system wherein the images are directly digitized using a CCD (charge coupled device) imager of one inch square or so has recently been put into practical use.
In this regard, in a case where the lungs of a subject, for example, are to be radiographed, an area necessary for the radiography is as large as about 43 cm×43 cm. Therefore, an optical apparatus for condensing the light of the whole area onto the CCD imager is necessitated, and the inevitable large size of the apparatus becomes a problem. A solid-state imaging device of flat panel detection type has been proposed as means for solving the problem. As an example of the device, an X-ray imaging device called “flat panel X-ray detector” is proposed in U.S. Pat. No. 4,689,487.
The above solid-state imaging device of flat panel detection type is characterized by employing a-SiTFTs (amorphous silicon thin-film transistors) as the control elements of photoelectric conversion pixels. Now, the structure of this device will be briefly explained.
A flat substrate made of a glass material is employed for the device. An insulating layer made of a silicon oxide film is formed on the substrate, and photoelectric conversion pixels each consisting of a capacitor, a TFT and an X-ray/charge conversion film are formed in the shape of a matrix on the insulating layer. Further, there are formed the wiring patterns of scanning lines for feeding switching control signals to the TFTs of the respective pixels arrayed in the row direction of the matrix, and the wiring patterns of signal lines for sequentially transferring stored charges read out from the respective pixels arrayed in the column direction. The substrate is called “TFT array substrate”.
With the device of the above construction, in each of the pixels, a bias voltage is applied to a capacitor forming portion through a capacitor line beforehand, and charges generated by the X-ray/charge conversion film are stored in the capacitor. The TFTs of the respective pixels are sequentially driven to turn ON through the scanning lines laid in row units, whereby the stored charges of the pixel capacitors are sequentially derived to the signal lines laid in column units. The stored charges of the individual pixels derived to the respective signal lines are amplified, and are digitally outputted. Thus, image data based on all the pixels can be obtained.
In the TFT array substrate, terminals for connections with circuit devices such as drive circuits, an amplification circuit and a power source circuit, which are prepared separately from the substrate itself, are formed at the respective terminating ends of the scanning lines, signal lines and capacitor lines. The terminals are put together by every predetermined number (each terminal shall be called a “PAD”, and the group of the terminals put together (the collection of PADs) shall be called a “PAD group”). By way of example, the terminals are arranged at a high density under the conditions of a terminal width of 60 &mgr;m and a terminal pitch of 100 &mgr;m.
A technique called “TAB (Tape Automated Bonding) connection” is employed for connecting the terminals and the circuit devices. The TAB connection implements the electrical connections among the terminals arranged at the high density, in such a way that a PAD region on the TFT array substrate and a PAD region on the side of a flexible circuit board, which is called a tape carrier package (TCP) and on which the circuit devices are mounted (hereinbelow, the circuit board shall be termed the “TCP”), are bonded by thermocompression bonding through an anisotropic conductive film (ACF) of thermosetting type.
Since the TFT array substrate is very expensive, it needs to be repaired at the time when any misconnection with the TCP has occurred. A repairing method in this case is such that the TCP thermally secured is torn off from the TFT array substrate, that the ACF secured on the surface of the substrate is removed with a solvent or the like, and that the substrate and the TCP which have been properly connected are bonded again by the thermocompression bonding through an ACF. In the prior art, therefore, the whole wiring patterns which include terminal forming portions are formed of a material which is difficult to peel off the substrate at the tearing-off of the TCP or at the removal of the ACF, for example, molybdenum-tungsten (MoW) which is used for the capacitor lines. Besides, a transparent conductive film of indium tin oxide (ITO) or the like is stacked as a protective layer on the terminal forming portions.
Meanwhile, an image of high definition and the reduction of image noise are required of the above solid-state imaging device of the flat panel detection type. For meeting the requirements, it is indispensable to lower the resistance of each signal line forming a factor for the image noise, and to reduce a capacitance parasitic to the signal line. It is desirable for the decrease of the parasitic capacitance of the signal line to fine the line width of each scanning line which intersects orthogonally to the signal line, and the use of a material of low resistance is mentioned as means for fining the scanning line with a predetermined driving speed satisfied. For attaining the lower resistances of the scanning line and the signal line, it is desirable to use, for example, an aluminum alloy.
The material such as aluminum alloy, however, weakly couples with the silicon oxide film. The terminals for the TAB connection are formed at the terminating ends of the wiring patterns which form the scanning lines and the signal lines. Therefore, in a case where the aluminum alloy is used as the material of the wiring patterns, even the wiring layers are peeled off at the removal of the ACF. For this reason, a new terminal structure of the TFT array substrate is demanded in points of facilitating the repair and improving the characteristics of the imaging device.
Incidentally, a technique which employs an aluminum alloy as a wiring material for elements arrayed in the shape of a matrix is proposed in Japanese Patent Laid-Open No. 2000-243558. The technique disclosed in the cited reference is as stated below.
With the object of raising a scanning drive speed simultaneously with heightening an integration density, the wiring patterns of scanning lines and signal lines for light emitting display elements are formed of the aluminum alloy. The terminating ends of the wiring patterns are shaped into terminals for connections with external circuit devices. The whole substrate except terminal portions are tightly sealed. On this occasion, when the aluminum alloy is exposed the terminal portion is corroded by oxidation. Therefore, the terminal portions
Tanaka Manabu
Tsukamoto Akira
Louie Wai-Sing
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pham Long
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