WO1996017385A1 - Thin film transistor for liquid crystal display and method for fabricating the same - Google Patents

Thin film transistor for liquid crystal display and method for fabricating the same Download PDF

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Publication number
WO1996017385A1
WO1996017385A1 PCT/KR1995/000112 KR9500112W WO9617385A1 WO 1996017385 A1 WO1996017385 A1 WO 1996017385A1 KR 9500112 W KR9500112 W KR 9500112W WO 9617385 A1 WO9617385 A1 WO 9617385A1
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WO
WIPO (PCT)
Prior art keywords
thin film
film transistor
gate electrode
electrode
high concentration
Prior art date
Application number
PCT/KR1995/000112
Other languages
French (fr)
Inventor
Seong Yeon Hwang
Dong Hyun Nam
Tae Gon Kim
Young Woo Seo
Seon Min Yeom
Original Assignee
Orion Electric Co. Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Orion Electric Co. Ltd. filed Critical Orion Electric Co. Ltd.
Priority to JP8518610A priority Critical patent/JP2835471B2/en
Priority to EP95930048A priority patent/EP0741911A1/en
Publication of WO1996017385A1 publication Critical patent/WO1996017385A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
    • H01L27/12—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/78—Field effect transistors with field effect produced by an insulated gate
    • H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
    • H01L29/49—Metal-insulator-semiconductor electrodes, e.g. gates of MOSFET
    • H01L29/4908—Metal-insulator-semiconductor electrodes, e.g. gates of MOSFET for thin film semiconductor, e.g. gate of TFT
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/78—Field effect transistors with field effect produced by an insulated gate
    • H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
    • H01L29/78645—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with multiple gate
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/136—Liquid crystal cells structurally associated with a semi-conducting layer or substrate, e.g. cells forming part of an integrated circuit
    • G02F1/1362—Active matrix addressed cells
    • G02F1/1368—Active matrix addressed cells in which the switching element is a three-electrode device

Definitions

  • the present invention relates to a thin film transistor (hereinafter referred to as "TFT") for liquid crystal display (hereinafter referred to as “LCD”) and a method for fabricating the same. More particularly, the present invention is concerned with the lowering of gate voltage through resistors formed at the conjunction between the outermost branches of a multiple gate electrode and the gate line, thereby reducing the leak current and improving the reliability in device operation.
  • TFT thin film transistor
  • LCD liquid crystal display
  • An LCD which is a kind of flat panel display, is operated by changing the optical anisotropy of the liquid crystal with the application of an elect-rical field, the liquid crystal having the fluidity of a liquid and the optical properties of a crystal.
  • LCDs consume lower power and have smaller volume than cathode ray tubes.
  • LCDs can constitute a very large and highly defined screen, which is virtually impossible for cathode ray tubes to accomplish. By virtue of such advantages, LCDs substitute for cathode ray tubes and are increasingly employed in many fields.
  • An LCD comprises liquid crystal sandwiched between a lower liquid crystal plate which is connected with a switching device and has a pixel electrode and an upper liquid crystal plate which has a common electrode.
  • an LCD is prepared as follows. First, a transparent electrode pattern and a pixel electrode made of indium tin oxide (hereinafter referred to as "ITO") is formed on a transparent substrate, for example, quartz. Then, a passivation film is formed to prevent the short circuit of the transparent electrode pattern, followed by the formation of an alignment film to align the liquid crystal. Thereafter, valleys with an orientation are formed on the alignment film, which is accomplished by rubbing the film with a rubbing roll in which cloth is wound around a cylindrical core. As a result, a lower liquid crystal substrate is obtained. An upper liquid crystal substrate having a common electrode is made. Thereafter , ' the upper liquid crystal substrate and the lower liquid crystal substrate are sealed by forming spacers and seal patterns to provide a certain cell gap therebetween. LCD is completed by injecting liquid crystal into the cell gap and sealing it.
  • ITO indium tin oxide
  • Such LCD is typically subgrouped into twisted nematic (TN) , super twisted nematic (STN) , ferroelectric, and TFT LCD, according to the kind and operating manner of the liquid crystal employed.
  • TN twisted nematic
  • STN super twisted nematic
  • ferroelectric ferroelectric
  • TFT LCD TFT LCD
  • TFT LCD which employs TFT as a switching device for the operation of pixel, responds more quickly and has wider viewing angle than do other LCDs.
  • TFT LCDs can produce a large, highly defined picture, they are extensively used in portable televisions, laptop personal computers and the like.
  • TFT structures that are different in the position of an active layer, a semiconductor layer pattern: Staggered type in which a gate electrode and a source/drain electrode are divided by the semiconductor layer; and Coplanar type in which a gate electrode and a source/drain electrode both are formed at one side of the semiconductor layer .
  • a significant problem of such TFT LCD is that the aperture ratio is low because on the partial area of a pixel a TFT device is formed and gate bus and data bus lines are arranged to operate the device.
  • a conventional TFT for LCD will be described in conjunction with Fig. l, which is a layout showing a top gate-type TFT in which a gate electrode is formed in the upper side of the channel of a semiconductor layer.
  • the top gate-type TFT has a substrate l, made of a transparent material, i.e, quartz, in which a rectangular semiconductor layer pattern 2 of amorphous or polycrystalline silicon is formed as a channel. Over the entire surface of the resulting structure, a gate insulating film, e.g, an oxide film (not shown) is formed. A triple gate electrode 3 is formed on an area of the gate insulating film over the predetermined part of the semiconductor layer pattern 2 to be the channel.
  • the triple gate electrode 3 is made of a polysilicon layer containing a high concentration of impurities. One end of the gate electrode is connected with a gate line 10, which extends in the horizontal direction to the transparent substrate 1.
  • a high concentration N * impurity layer 4 is formed in some areas of the semiconductor layer pattern 2 which are nonoverlapped with the triple gate electrode 3. Following this, a blanket field oxide film (not shown) is formed over the resulting structure. Contact holes 7 are formed to expose the high concentration N * impurity layer 4 partially. Then, a source electrode 5 and a drain electrode 6 are formed to come into contact with the high concentration impurity layer 4 through the contact holes 7. The source electrode 5 and the drain electrode 6 are connected with a data line extending in the vertical direction and a transparent pixel electrode 12, respectively.
  • the described conventional TFT for LCD having such multiple gate electrode is a structure which is capable of scattering the electric field applied to the gate electrode, so as to prevent the increase of leak current caused by grain boundary, a significant disadvantage of polysilicon gate.
  • a TFT for LCD comprising: a semiconductor layer pattern formed on a transparent substrate,- a blanket gate insulating film formed over the entire surface of the resulting structure; a multiple gate electrode formed on the gate insulating film over the part predetermined as channel of the semiconductor pattern, whose one end contacts with a gate line; resistors formed between each of the outermost branches of the multiple gate electrode and the gate line; high concentration impurity layers formed in the semiconductor layer pattern, which are nonoverlapped with and present outside the multiple gate electrode; a source electrode whose one end is in contact with one of the high concentration impurity layers while the other end is connected with a data line; and a drain electrode whose one end is in contact with the other high concentration impurity layer while the other end is connected with a pixel electrode.
  • a method for fabricating a TFT for LCD comprising the steps of: forming a semiconductor layer pattern on a transparent substrate; depositing a blanket gate insulating layer over the resulting structure,* forming a multiple gate electrode extending across the upper part of the semiconductor layer pattern; forming high concentration impurity layers in some areas of the semiconductor layer pattern which are nonoverlapped with the outermost branches of the multiple gate electrode; implanting impurities into the multiple gate electrode lest any impurity is present between each of the outermost branches of the multiple gate electrode and a gate line, so as to form a resistor therebetween; forming a blanket field oxide film on the resulting structure; partially exposing the high concentration impurity layers; and forming a source electrode and a drain electrode in contact with the exposed high concentration impurity layers.
  • Fig. l is a layout illustrating a TFT for LCD, according to a conventional technique
  • Fig. 2 is a layout illustrating a TFT for LCD, according to the present invention.
  • FIG. 2 there is a layout showing a TFT for LCD, according to the present invention.
  • the structure and the fabricating method of the TFT of the present invention will be, in detail, described in conjunction with Fig. 2.
  • a rectangular semiconductor layer pattern with a predetermined width which is made of amorphous or polycrystalline silicon, is formed on a substrate made of a transparent material, for example, quartz or glass, followed by the formation of a blanket gate insulating film (not shown), i.e. an oxide film, over the resulting structure.
  • a blanket gate insulating film i.e. an oxide film
  • a triple gate electrode 3 is formed on a part of the gate insulating film which is overlapped with the central part of the semiconductor layer pattern 2.
  • the gate electrode 3 is intrinsic or contains impurities at a low concentration and brings its one end into contact with a gate line 10 which extends in the vertical direction.
  • N or P type ions are implanted into areas of the semiconductor layer pattern 2 which are nonoverlapped with the triple gate electrode 3, so as to form a high concentration impurity layer 4, while they are not allowed to be implanted into the gate electrode 3.
  • photosensitive film patterns (not shown) are formed between each of the two outermost branches of the triple gate electrode 3 and the gate line 10. N or P type impurities are implanted at a high concentration into the gate electrode 3 and the gate line 10, with the aim of reducing resistance, while the photosensitive film patterns serve as a mask.
  • resistors 8 which are intrinsic or contain impurities at a low concentration.
  • a blanket field oxide film (not shown) is formed over the resulting structure.
  • Contact holes 7 which partially expose the high concentration N + impurity layer are formed by removing the predetermined parts of the field oxide film and the gate oxide film in sequence.
  • a source electrode 5 and a drain electrode 6 are formed in such a way to come into contact with the high concentration impurity layer 4 through the contact holes 7. While the source electrode 5 is connected with a data line 11 which extends in the vertical direction, the drain electrode 6 is connected with a pixel electrode such as ITO.
  • the gate voltage can be lowered at the outermost branches of the triple gate electrode 3 by the resistors 8, which allows the electric field to be changed smoothly and thus, results in the reduction of leak current.
  • the gate voltage is lowered by the resistors in the TFT structure of the present invention, the leak current attributable to the voltage applied by the source/drain electrodes can be reduced, which brings about an effect that the reliability in device operation is significantly improved.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Ceramic Engineering (AREA)
  • Liquid Crystal (AREA)
  • Thin Film Transistor (AREA)

Abstract

A TFT for LCD and a method fabricating the same, characterized by the formation of resistors at the conjunction between each of the outermost branches of a multiple gate electrode made of polysilicon and the gate line, the branches being adjacent to a source electrode and a drain electrode respectively. By virtue of the resistors, the voltage between the branches and the gate line can be lowered. The resistors are the polysilicon itselft or are implanted by impurities at a low concentration. The gate voltage is significantly reduced by the resistors such that the leak current attributable to the voltage applied to the source/drain electrodes can be significantly reduced, thereby improving the reliability of device.

Description

THIN FILM TRANSISTOR FOR LIQUID CRYSTAL DISPLAY AND METHOD FOR FABRICATING THE SAME
Technical Field
The present invention relates to a thin film transistor (hereinafter referred to as "TFT") for liquid crystal display (hereinafter referred to as "LCD") and a method for fabricating the same. More particularly, the present invention is concerned with the lowering of gate voltage through resistors formed at the conjunction between the outermost branches of a multiple gate electrode and the gate line, thereby reducing the leak current and improving the reliability in device operation.
Background Art
An LCD, which is a kind of flat panel display, is operated by changing the optical anisotropy of the liquid crystal with the application of an elect-rical field, the liquid crystal having the fluidity of a liquid and the optical properties of a crystal. LCDs consume lower power and have smaller volume than cathode ray tubes. In addition, LCDs can constitute a very large and highly defined screen, which is virtually impossible for cathode ray tubes to accomplish. By virtue of such advantages, LCDs substitute for cathode ray tubes and are increasingly employed in many fields.
An LCD comprises liquid crystal sandwiched between a lower liquid crystal plate which is connected with a switching device and has a pixel electrode and an upper liquid crystal plate which has a common electrode.
Generally, an LCD is prepared as follows. First, a transparent electrode pattern and a pixel electrode made of indium tin oxide (hereinafter referred to as "ITO") is formed on a transparent substrate, for example, quartz. Then, a passivation film is formed to prevent the short circuit of the transparent electrode pattern, followed by the formation of an alignment film to align the liquid crystal. Thereafter, valleys with an orientation are formed on the alignment film, which is accomplished by rubbing the film with a rubbing roll in which cloth is wound around a cylindrical core. As a result, a lower liquid crystal substrate is obtained. An upper liquid crystal substrate having a common electrode is made. Thereafter , ' the upper liquid crystal substrate and the lower liquid crystal substrate are sealed by forming spacers and seal patterns to provide a certain cell gap therebetween. LCD is completed by injecting liquid crystal into the cell gap and sealing it.
Such LCD is typically subgrouped into twisted nematic (TN) , super twisted nematic (STN) , ferroelectric, and TFT LCD, according to the kind and operating manner of the liquid crystal employed.
TFT LCD, which employs TFT as a switching device for the operation of pixel, responds more quickly and has wider viewing angle than do other LCDs. In addition, since TFT LCDs can produce a large, highly defined picture, they are extensively used in portable televisions, laptop personal computers and the like.
There are two TFT structures that are different in the position of an active layer, a semiconductor layer pattern: Staggered type in which a gate electrode and a source/drain electrode are divided by the semiconductor layer; and Coplanar type in which a gate electrode and a source/drain electrode both are formed at one side of the semiconductor layer .
A significant problem of such TFT LCD is that the aperture ratio is low because on the partial area of a pixel a TFT device is formed and gate bus and data bus lines are arranged to operate the device.
In order to better understand the background of the invention, a conventional TFT for LCD will be described in conjunction with Fig. l, which is a layout showing a top gate-type TFT in which a gate electrode is formed in the upper side of the channel of a semiconductor layer.
As shown in Fig. 1, the top gate-type TFT has a substrate l, made of a transparent material, i.e, quartz, in which a rectangular semiconductor layer pattern 2 of amorphous or polycrystalline silicon is formed as a channel. Over the entire surface of the resulting structure, a gate insulating film, e.g, an oxide film (not shown) is formed. A triple gate electrode 3 is formed on an area of the gate insulating film over the predetermined part of the semiconductor layer pattern 2 to be the channel. The triple gate electrode 3 is made of a polysilicon layer containing a high concentration of impurities. One end of the gate electrode is connected with a gate line 10, which extends in the horizontal direction to the transparent substrate 1. A high concentration N* impurity layer 4 is formed in some areas of the semiconductor layer pattern 2 which are nonoverlapped with the triple gate electrode 3. Following this, a blanket field oxide film (not shown) is formed over the resulting structure. Contact holes 7 are formed to expose the high concentration N* impurity layer 4 partially. Then, a source electrode 5 and a drain electrode 6 are formed to come into contact with the high concentration impurity layer 4 through the contact holes 7. The source electrode 5 and the drain electrode 6 are connected with a data line extending in the vertical direction and a transparent pixel electrode 12, respectively.
The described conventional TFT for LCD having such multiple gate electrode is a structure which is capable of scattering the electric field applied to the gate electrode, so as to prevent the increase of leak current caused by grain boundary, a significant disadvantage of polysilicon gate.
In spite of this, a leak current occurs in such conventional structure employing the triple gate electrode, degrading the reliability in device, which is attributed to the fact that the two outermost parts of the multiple gate electrode are applied with a large electric field owing to the voltage applied to the source/drain electrode and the gate voltage.
Disclosure of Invention
Accordingly, it is a principal object of the present invention to provide a TFT for LCD which has a resistance at the conjunction between each of the outermost branches of multiple gate electrode and the gate line, thereby reducing the leak current owing to the voltage applied to the gate electrode and improving the reliability in device operation.
It is another object of the present invention to provide a method for fabricating such TFT for LCD.
In accordance with an aspect of the present invention, there is provided a TFT for LCD, comprising: a semiconductor layer pattern formed on a transparent substrate,- a blanket gate insulating film formed over the entire surface of the resulting structure; a multiple gate electrode formed on the gate insulating film over the part predetermined as channel of the semiconductor pattern, whose one end contacts with a gate line; resistors formed between each of the outermost branches of the multiple gate electrode and the gate line; high concentration impurity layers formed in the semiconductor layer pattern, which are nonoverlapped with and present outside the multiple gate electrode; a source electrode whose one end is in contact with one of the high concentration impurity layers while the other end is connected with a data line; and a drain electrode whose one end is in contact with the other high concentration impurity layer while the other end is connected with a pixel electrode.
In accordance with another aspect of the present invention, there is provided a method for fabricating a TFT for LCD, comprising the steps of: forming a semiconductor layer pattern on a transparent substrate; depositing a blanket gate insulating layer over the resulting structure,* forming a multiple gate electrode extending across the upper part of the semiconductor layer pattern; forming high concentration impurity layers in some areas of the semiconductor layer pattern which are nonoverlapped with the outermost branches of the multiple gate electrode; implanting impurities into the multiple gate electrode lest any impurity is present between each of the outermost branches of the multiple gate electrode and a gate line, so as to form a resistor therebetween; forming a blanket field oxide film on the resulting structure; partially exposing the high concentration impurity layers; and forming a source electrode and a drain electrode in contact with the exposed high concentration impurity layers.
Brief Description of Drawings
The above objects and other advantages of the present invention will become more apparent by describing in detail the preferred embodiments of the present invention with reference to the attached drawings in which: Fig. l is a layout illustrating a TFT for LCD, according to a conventional technique; and
Fig. 2 is a layout illustrating a TFT for LCD, according to the present invention.
Best Mode for Carrying Out the Invention
Referring to Fig. 2, there is a layout showing a TFT for LCD, according to the present invention. The structure and the fabricating method of the TFT of the present invention will be, in detail, described in conjunction with Fig. 2.
First, a rectangular semiconductor layer pattern with a predetermined width, which is made of amorphous or polycrystalline silicon, is formed on a substrate made of a transparent material, for example, quartz or glass, followed by the formation of a blanket gate insulating film (not shown), i.e. an oxide film, over the resulting structure.
Next, a triple gate electrode 3 is formed on a part of the gate insulating film which is overlapped with the central part of the semiconductor layer pattern 2. The gate electrode 3 is intrinsic or contains impurities at a low concentration and brings its one end into contact with a gate line 10 which extends in the vertical direction.
Then, N or P type ions are implanted into areas of the semiconductor layer pattern 2 which are nonoverlapped with the triple gate electrode 3, so as to form a high concentration impurity layer 4, while they are not allowed to be implanted into the gate electrode 3.
Following this, photosensitive film patterns (not shown) are formed between each of the two outermost branches of the triple gate electrode 3 and the gate line 10. N or P type impurities are implanted at a high concentration into the gate electrode 3 and the gate line 10, with the aim of reducing resistance, while the photosensitive film patterns serve as a mask.
Removal of the photosensitive film patterns results in resistors 8, which are intrinsic or contain impurities at a low concentration.
Subsequently, a blanket field oxide film (not shown) is formed over the resulting structure. Contact holes 7 which partially expose the high concentration N+ impurity layer are formed by removing the predetermined parts of the field oxide film and the gate oxide film in sequence. Then, a source electrode 5 and a drain electrode 6 are formed in such a way to come into contact with the high concentration impurity layer 4 through the contact holes 7. While the source electrode 5 is connected with a data line 11 which extends in the vertical direction, the drain electrode 6 is connected with a pixel electrode such as ITO.
In the above-described TFT for LCD, the gate voltage can be lowered at the outermost branches of the triple gate electrode 3 by the resistors 8, which allows the electric field to be changed smoothly and thus, results in the reduction of leak current.
Although a triple gate electrode is described in this specification, the effect of reduction in leak current could be obtained in any TFT having more multiple gate electrodes provided such that resistors are employed only at the two outermost branches of the multiple gate electrode, in accordance with the present invention.
As described hereinbefore, since the gate voltage is lowered by the resistors in the TFT structure of the present invention, the leak current attributable to the voltage applied by the source/drain electrodes can be reduced, which brings about an effect that the reliability in device operation is significantly improved.
Other features, advantages and the embodiment of the invention disclosed herein will be readily apparent to those exercising ordinary skill after reading the foregoing disclosures. In this regard, while a specific embodiment of the invention has been described in considerable detail, variations and modifications of this embodiment can be effected without departing from the spirit and scope of the invention as described and claimed.

Claims

Claims :
1. A thin film transistor for liquid crystal display, comprising: a semiconductor layer pattern formed on a transparent substrate; a blanket gate insulating film formed over the entire surface of the resulting structure; a multiple gate electrode formed on the gate insulating film over the part predetermined as channel of the semiconductor pattern, whose one end contacts with a gate line; resistors formed between each of the outermost branches of the multiple gate electrode and the gate line; high concentration impurity layers formed in the semiconductor layer pattern, which are nonoverlapped with and present outside the multiple gate electrode; a source electrode whose one end is in contact with one of the high concentration impurity layers while the other end is connected with a data line; and a drain electrode whose one end is in contact with the other high concentration impurity layer while the other end is connected with a pixel electrode.
2. A thin film transistor in accordance with claim 1, wherein said transparent substrate is comprised of quartz or glass.
3. A thin film transistor in accordance with claim 1, wherein said semiconductor layer pattern is comprised of polysilicon.
4. A thin film transistor in accordance with claim l, wherein said gate electrode is comprised of polysilicon which is intrinsic or has impurities at a low concentration.
5. A thin film transistor in accordance with claim 1, wherein said source electrode and said drain electrode are comprised respectively of any one selected from the group consisting of titanium, chrome and aluminum.
6. A thin film transistor in accordance with claim 1, wherein said gate insulating film is comprised of an oxide.
7. A thin film transistor in accordance with claim 1, wherein said high concentration impurity layers are of N or P type.
8. A method for fabricating a thin film transistor for liquid crystal display, comprising the steps of: forming a semiconductor layer pattern on a transparent substrate; depositing a blanket gate insulating layer over the resulting structure; forming a multiple gate electrode extending across the upper part of the semiconductor layer pattern; forming high concentration impurity layers in some areas of the semiconductor layer pattern which are nonoverlapped with the outermost branches of the multiple gate electrode; implanting impurities into the multiple gate electrode lest any impurity is present between each of the outermost branches of the multiple gate electrode and a gate line, so as to form a resistor therebetween; forming a blanket field oxide film on the resulting structure; partially exposing the high concentration impurity layers; and forming a source electrode and a drain electrode in contact with the exposed high concentration impurity layers.
PCT/KR1995/000112 1994-11-30 1995-08-31 Thin film transistor for liquid crystal display and method for fabricating the same WO1996017385A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP8518610A JP2835471B2 (en) 1994-11-30 1995-08-31 Thin film transistor for liquid crystal display device and method of manufacturing the same
EP95930048A EP0741911A1 (en) 1994-11-30 1995-08-31 Thin film transistor for liquid crystal display and method for fabricating the same

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Application Number Priority Date Filing Date Title
KR1019940031941A KR0151876B1 (en) 1994-11-30 1994-11-30 Thin film transistor for lcd and its making method
KR1994/31941 1994-11-30

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WO2001050513A1 (en) * 2000-01-07 2001-07-12 Seiko Epson Corporation Thin film transistor
WO2001050514A1 (en) * 2000-01-07 2001-07-12 Seiko Epson Corporation Thin film transistor
US6580129B2 (en) 2000-01-07 2003-06-17 Seiko Epson Corporation Thin-film transistor and its manufacturing method

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KR100769433B1 (en) * 2006-12-04 2007-10-22 삼성에스디아이 주식회사 Thin film transistor, method of manufacturing the thin film transistor and flat panel display device having the thin film transistor

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EP0342925A2 (en) * 1988-05-17 1989-11-23 Seiko Epson Corporation Active matrix panel
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001050513A1 (en) * 2000-01-07 2001-07-12 Seiko Epson Corporation Thin film transistor
WO2001050514A1 (en) * 2000-01-07 2001-07-12 Seiko Epson Corporation Thin film transistor
US6528830B1 (en) 2000-01-07 2003-03-04 Seiko Epson Corporation Thin film transistor
US6548356B2 (en) 2000-01-07 2003-04-15 Seiko Epson Corporation Thin film transistor
US6580129B2 (en) 2000-01-07 2003-06-17 Seiko Epson Corporation Thin-film transistor and its manufacturing method

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JPH09502056A (en) 1997-02-25
KR0151876B1 (en) 1998-10-01
JP2835471B2 (en) 1998-12-14
EP0741911A1 (en) 1996-11-13
KR960019778A (en) 1996-06-17

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