Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
2002-07-03
2004-03-30
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
Reexamination Certificate
active
06713324
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thin film transistor and a method for manufacturing the transistor and more particular, to an image display device having such thin film transistors built therein and a method for manufacturing the display device.
With respect to a TFT type liquid-crystal display device having thin film transistors (which will be referred to as TFT's, hereinafter), there is disclosed a TFT liquid-crystal display device with a circuit built therein (which will be also referred to as the circuit built-in type TFT liquid-crystal display device, hereinafter) wherein a pixel switching element and a display pixel region peripheral circuit make up a polycrystalline silicon TFT, e.g., in JP-A-64-2088.
There is also disclosed such a circuit built-in type TFT liquid-crystal display device, for the purpose of attaining a high circuit performance, which is improved in its TFT mobility by growing a silicon crystal largely in a specific direction to align a source/drain arrangement direction (current direction) nearly with the longitudinal direction of crystal grains, e.g., in JP-A-11-121753.
Further, in such a liquid-crystal display device as disclosed in an embodiment of, e.g., JP-A-2000-243970, a TFT source/drain arrangement direction (current direction) is aligned nearly with the longitudinal direction of crystal grains, and respective TFT's are arranged in horizontal and vertical blocks (in horizontal and vertical directions) at a display pixel array periphery when the TFT's are viewed from the front side surface of an array substrate. However, this display device fails to show a specific example of the TFT arrangement.
In the aforementioned JP-A-11-121753 of the TFT type wherein the current direction from the drain to the source is aligned nearly with the longitudinal direction of crystal grains, the performance of each TFT can be improved. However, since the current direction is limited to the horizontal (horizontal block) direction or vertical (vertical block) direction, this restricts the TFT array when layout design is made about a pixel array or a peripheral circuit, thus increasing a circuit occupation surface area.
In order to avoid such restriction to some extent, in the case of the embodiment shown in FIG. 1 in the aforementioned JP-A-2000-243970, laser irradiation is carried out in two horizontal and vertical directions, so that TFT's are arranged in the horizontal (horizontal block) direction and in the vertical (vertical block) direction. In the known example, when the TFT array is viewed on an identical straight line of the horizontal or vertical direction, the horizontal direction TFT's are arranged as not mixed with the vertical direction TFT's in the source/drain arrangement direction (current direction), no TFT is formed by laser irradiation so as to arranged at a corner of the display device and at a pixel array, which results in limitation of a high-performance TFT array.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention, in order to solve the above problems in the prior art, to provide an image display device wherein high-performance TFT's having a source/drain arrangement direction (current direction) substantially aligned with the longitudinal direction of crystal grains are arranged in a display pixel array, in a peripheral circuit in the vicinity thereof or in all or some of corners of the display device, TFT's (which will be referred to as horizontal-direction TFT's, hereinafter) in a horizontal (horizontal block) direction or TFT's (which will be referred to as vertical-direction TFT's, hereinafter) in a vertical (vertical block) direction are arranged so that the current directions of sources and drains in the horizontal-direction or vertical-direction TFT's are arranged in rows in the horizontal or vertical direction when viewed from the surface of a silicon film, or the TFT blocks in the horizontal and vertical directions when viewed from an identical straight line of the horizontal or vertical direction are mixedly provided.
Another object of the present invention is to provide a method for manufacturing an image display device which can easily manufacture the image display device mixedly including horizontal direction TFT's and vertical direction TFT's.
The invention of the present invention is summarized as follows.
The present invention is directed to an image display device driven by thin film transistors formed on a substrate, wherein the thin film transistors are made of a polycrystalline silicon film formed on the substrate, crystal grains of the polycrystalline silicon film are grown in a specific direction within the surface of the silicon film to be long in its growth direction and short in a direction substantially perpendicular thereto, an arrangement direction (current direction) of a source and drain of the thin film transistors is substantially aligned with a longitudinal direction of the crystal grains, the thin film transistors are divided into blocks each including at least one of the thin film transistor within the surface of the silicon film, at least one of the blocks is present in a periphery of a display pixel array, a arrangement direction of a source and drain of a plurality of thin film transistors included in the block is aligned with a horizontal or vertical direction when viewed from the surface of the silicon film within the same block, a plurality of the blocks are present when viewed from an identical straight line of the horizontal or vertical direction., and at least one location where blocks including the thin film transistors with the arrangement direction (current direction) of source and drains thereof arranged in the horizontal and vertical directions are mixedly provided.
The present invention is also directed to an image display device driven by thin film transistors formed on a substrate, wherein the thin film transistors are made of a polycrystalline silicon film formed on the substrate, crystal grains of the polycrystalline silicon film are grown in a specific direction within a surface of the silicon film to be long in its growth direction and short in a direction substantially perpendicular thereto, a arrangement direction (current direction) of a source and drain of the thin film transistors is substantially aligned with a longitudinal direction of the crystal grains, the thin film transistors are divided into rectangular blocks each including at least one of the thin film transistors within the surface of the silicon film, at least one of the blocks is present in at least one corner of the display device or in a part of periphery of a display pixel array, a arrangement direction (current direction) of a source and drain of a plurality of thin film transistors included in the block is aligned with a horizontal or vertical direction when viewed from the surface of the silicon film within the same block, the arrangement direction (current direction) of the source and drain of the thin film transistors are in the horizontal or vertical direction, or the horizontal and vertical direction blocks are mixedly provided.
In a preferred embodiment of the present invention, the block includes at least one display pixel array selected from the group of a buffer circuit for driving thin film transistors in display pixels, a sampling switch circuit, a precharging circuit, a shift register circuit, a decoder circuit, a clock waveform trimming circuit, a digital-analog converter circuit, a power voltage transformer circuit, a level shifter circuit, a timing controller circuit, an amplifier circuit, a memory, a processor, a gate array and a communication circuit.
In a preferred embodiment of the present invention, the block includes a pixel driving circuit, a pixel memory or a pixel inverter circuit in the display pixel array.
The present invention is further directed to a method for manufacturing an image display device driven by thin film transistors of a polycrystalline silicon film
Hatano Mutsuko
Park Seong-kee
Shiba Takeo
Yamaguchi Shin'ya
Hitachi , Ltd.
Le Thao
Miles & Stockbridge P.C.
Nelms David
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