c12) United States Patent
`Kuriyagawa et al.
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 8,409,891 B2
`Apr. 2, 2013
`
`(54) DISPLAY DEVI℃E ANDMANUFA1℃TURING
`METHOD THEREOF
`
`(75) Inventors: Takeshi Kuriyagawa, Mobara (JP); Jun
`Fujiyoshi, Mobara (JP)
`
`(73) Assignees: Hitachi Displays, Ltd., Chiba (JP);
`Panasonic Liquid ℃rystal Display ℃o叫
`Ltd., Hyogo (JP)
`
`( * ) Notice: Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 35 days.
`
`(21) Appl. No.: 13/085,517
`
`(22) Filed:
`
`Apr. 13, 2011
`
`2004/0164297 Al* 8/2004 Kaneko et al.・0・...........・ e・.257/59
`2004/0245923 Al* 12/2004 Park et al.
`313/505
`2005/0285987 Al 12/2005 Azumada et al.
`438/17
`2007/0004062 Al* 1/2007 Yamazaki et al.
`2009/0256477 Al* 10/2009 Chung et al. .・ e・e・............313/505
`
`JP
`JP
`
`FOREIGN PATENT DOCUMENTS
`2006-39509
`2/2006
`2009-157200
`7 /2009
`
`* cited by examiner
`
`Primary Examiner Marcos D. Pizarro
`Assistant Examiner Bilkis Jahan
`(74) Attorney, Agent, or Firm Antonelli, Te汀 y,Stout &
`Kraus, LLP.
`
`(65)
`
`Prior Publication Data
`
`(57)
`
`ABSTRA℃I
`
`US 2011/0254006 Al Oct. 20, 2011
`
`(30)
`
`Foreign Application Priority Data
`
`Apr. 20, 2010 (JP) ............................... 2010-097034
`
`(51) Int. Cl.
`HOJL2ll仰 （2006.01)
`(52) Uふ Cl. ......・ H ・.438/34; 257厄33.004;257厄33.003;
`257厄 33.064
`( 58) Field of℃lassification Search ................... 438/34;
`257/E33.004, E33.003, E33.064
`See application file for complete search history.
`
`(56)
`
`References ℃ited
`
`U.S. PATENT DOCUMENTS
`7,948,167B2* 5/2011 Chungetal.
`2003/0201716 Al* 10/2003 Yamazaki eta!.
`
`313/504
`313/506
`
`A display device in which a plurality of gate wires and a
`plurality of drain wires that intersect the gate wires are pro-
`vided, and thin film transistors connected to the gate wires
`and the drain wires are formed for respective pixel regions. At
`least one of the gate wires, the drain wires, and lead wires
`drawn from the gate wires or the drain wires is formed of a
`light-transmitting patterned conductive film.百1elight-trans-
`mitting patterned conductive film is formed of at least a first
`light-transmitting patterned conductive film, and a second
`light-transmitting patterned conductive film laminated on the
`first light-transmi壮ingpatterned conductive film. The second
`light-transmitting pa恥 medconductive film is formed of a
`conductive film for coating only the surface of the first light-
`transmitting patterned conductive film including its side wall
`surface.
`
`7℃laims, 6 Drawing Sheets
`
`TFT
`
`CNL
`
`PAS
`
`IN2
`
`IN1
`
`GT
`
`GI
`
`GRL SUB1
`
`1
`
`SEL 2006
`Bluehouse v. SEL
`IPR2018-01405
`
`

`

`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 1 of 6
`
`US 8,409,891 B2
`
`FIG. 1
`
`SUB1,SUB2
`
`A
`
`GL
`
`GL
`
`PX
`
`TFT
`
`SL
`
`SEC
`
`SUB2
`
`SUB1
`
`2
`
`

`

`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 2 of 6
`
`US 8,409,891 B2
`
`FIG. 2
`
`GL
`
`DL
`
`PX
`
`DL
`
`PS
`
`_jB
`
`y
`
`x
`
`TFT
`
`GL
`
`3
`
`

`

`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 3 of 6
`
`US 8,409,891 B2
`
`FIG. 3
`
`TFT
`
`PX2
`PX1
`
`CNL
`
`CNL
`
`IN2
`
`IN1
`
`PAS
`
`IN2
`
`IN1
`
`GT
`
`GI
`
`GRL SUB1
`
`FIG. 4
`
`TFT
`
`PX1
`
`GT
`
`GI
`
`GRL SUB1
`
`4
`
`

`

`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 4 of 6
`
`US 8,409,891 B2
`
`FIG. 5
`
`TFT
`
`ITO
`
`PX1
`
`CNL
`
`CNL
`
`PAS
`
`IN2
`
`IN1
`
`PAS
`
`IN2
`
`IN1
`
`GT
`
`GI
`
`GRL SUB1
`
`FIG. 6
`
`TFT
`
`IT01
`
`GT
`
`GI
`
`SUB1
`
`5
`
`

`

`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 5 of 6
`
`US 8,409,891 B2
`
`FIG. 7
`
`TFT
`
`IN2
`
`IN1
`
`GT
`
`GI
`
`GRL SUB1
`
`FIG. 8
`
`睡醐謹輯躍罷醐
`
`同2
`
`sJs1
`
`FIG. 9
`
`ITO
`
`：〈：．：
`
`.・
`
`.·・v・·.··~且.II.LIL且.JLILJI..且3四人．．・．．．・·.···.··・.··・.··・．・＼人／γ＼・｜
`
`IT03
`
`SUB1
`
`6
`
`

`

`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 6 of 6
`
`US 8,409,891 B2
`
`FIG. 10
`
`IT01
`
`ITO
`
`FIG. 11
`
`FIG. 12
`
`FIG. 13
`
`PX−−−−ト
`
`IT03
`
`SUB1
`
`IT03
`
`SUB1
`
`IT03
`
`SUB1
`
`L→
`” ↓〜＿＿， CT
`• I
`・ー
`ーー” ・ー
`
`7
`
`

`

`US 8,409,891 B2
`
`1
`DISPLAY DEVI℃E ANDMANUFA1℃TURING
`METHOD THEREOF
`
`CLAIM OF PRIORITY
`
`BACKGROUND
`
`SUMJ\ι生RY
`
`百1epresent application claims priority from Japanese
`Patent Application JP 2010-097034 filed on Apr. 20, 2010, the
`content of which is hereby incorporated by reference into this
`application.
`
`2
`Generally, a metal filmれhinmetal film) is used for forming
`the leading wires in the frame region, and the drain and the
`gate wires provided in the display region for suppressing
`increase in the wiring load. The thin metal film exhibits low
`5 corrosion resistance, and accordingly, the material for form-
`ing the wiring layer to be provided at the position that is likely
`to be corroded has been demanded. It is therefore preferable
`to use the light transmitting conductive film such as ITO
`(Indium Tin Oxide) with corrosion resistance. However, the
`10 sheet resistance of the light-transmitting conductive film such
`as ITO is strong. Ifit is used for forming the wiring, the wiring
`resistance may be increased, causing the risk of increase in
`百1epresent invention relates to a display device and a the wiring load.
`manufacturing method thereof, and particularly, to a display
`When using the ITO with large sheet resistance as wiring,
`device using a light-transmitting conductive film.
`15 the wiring width may be increased. Such structure makes it
`Generally, a liquid crystal display device has a microfab- difficult to realize the na汀 owframe. Meanwhile, the film
`ricated electronic circuit formed on a surface at a liquid crys- thickness of ITO may also be considered. Generally, etching
`tal side of one of paired substrates oppositely provided having solution of oxalic acid is used after forming the light-trans-
`the liquid crystal interposed therebetw民 n.A display region mitting conductive film as ITO so as to be processed into a
`( display portion) having a plurality of pixels arranged in 20 desired pa壮 ぽn.In the process, the crystalline state of the
`matrix, and a peripheral circuit region (peripheral circuit por- light-transmitting conductive film needs to be non-crystalline
`tion) as a peripheral part of the display portion are formed on (amorphous). If the light-transmitting conductive film is crys-
`a surface of the other substrate at the liquid crystal side. The tallized, it camiot be etched by the etching solution of the
`electronic circuits are provided in the display portion and the aforementioned type. When forming the light-transmi壮ing
`peripheral circuit portion.
`25 conductive film with large film thickness, the resultant reac-
`百1eelectronic circuit in the display portion includes at tion heat allows easy crystallization. Tl山 iswhy the film
`least a thin-film transistor for selecting a group of pixels thickness of the light-transmitting conductive自lmis limited,
`a汀 angedin rows, and a pixel electrode to which a video signal resulting in difficulty in formation of the light-transmitting
`is supplied through the thin-film transistor. The electronic conductive film with the film thickness larger than the prede-
`circuit in the peripheral circuit portion includes a large num- 30 termined value.百1ewiring formed using the light-transmit-
`ber of the thin-film transistors for generating a signal ( scan ting conductive film generally tends to exhibit relatively large
`signal) that drives the thin-film transistor of the display por- electric resistance.
`tion, and the video signal.
`Each of the electronic circuits in the display portion and the
`peripheral circuit portion is configured by laminating a pat- 35
`The present invention provides the display device which
`terned conductive film, a semiconductor film, and an insulat-
`ing film in this order.百1eelectronic circuit in the display includes wirings and electrodes each formed of the light-
`portion is connected to a drain wire and a gate wire provided transmitting conductive film for ensuring the reduced resis-
`in the display region having pixels formed. The electronic tance.
`circuit in the peripheral circuit portion is connected to leading 40 The present invention白rtherprovides the manufacturing
`wires which extend from the drain wire and the gate wire in method of the display device provided with wirings and elec-
`the display region so as to output the video signal and the scan trodes each formed of the light-transmi壮ingconductive film
`signal to the drain wire and the gate wire via the leading wire. with reduced electric resistance without increasing process
`The electronic circuit in the peripheral circuit portion is con- steps.
`figured to receive input of the data for displaying from an 45 (1) The present invention provides a display device in which
`external device via a terminal portion. The terminal portion is
`a plurality of gate wires and a plurality of drain wires which
`int郎 氏tthe gate wires are formed on a substrate, pixel
`connected to the peripheral circuit via a wiring (terminal
`wiring), through which the display data is input to the elec-
`regions are defined by the gate wires and the drain wires,
`tror廿ccircuit as disclosed in Japanese Unexamined Patent
`and a thin film transistor connected to the gate wire and the
`so drain wire is formed for each of the pixel regions. At least
`Publication Nos. 2006-39509 and 2009-157200.
`The liquid crystal display device installed in the portable
`one of the gate wires, the drain wires, and a leading wire
`information terminal such as a cell phone has been demanded
`extending from the gate wire or the drain wire is formed of
`to achieve wide display region relative to the limited size of
`a light-transmitting patterned conductive film. The light-
`the casing, high-de白1itionperformance, and high-resolution
`transmitting patterned conductive film is formed of at least
`property. For this, in the generally employed liquid crystal 55 a first light-transmitting patterned conductive film, and a
`second light-transmitting pa壮ernedconductive film lami-
`display device, the display region is widened by reducing the
`space occupied by a frame region that is not related to the
`nated on the first light-transmitting patterned conductive
`image display (that is, narrow企組問）.Especially in the case
`film.百1esecond light-transmitting patterned conductive
`自lmis formed of a conductive film for coating a surface of
`where the electronic circuit in the peripheral circuit portion is
`not provided in the frame region, that is, the electronic circuit 60 the first light-transmitting patterned conductive film
`in the peripheral circuit portion is formed on the semiconduc-
`including its side wall surface.
`tor chip installed in the terminal portion, the technique is (2) The preset invention provides a manufacturing method of
`employed for bringing the leading wire in the frame region
`a display device having a thin film transistors in matrix
`into a multi-layer configuration to achieve the narrow frame,
`formed on a substrate, including a first film forming step of
`aiming at l首位−definitionand high image quality as disclosed 65 forming a first light transmi壮ingconductive film on a sub-
`in Japanese Unexamined Patent Publication Nos. 2006-
`strate, a first pattern step of providing a first light transmit-
`39509 and 2009-157200.
`ting patterned conductive film in patterned crystallized
`
`8
`
`

`

`US 8,409,891 B2
`
`3
`4
`state by subjecting the first light-transmitting conductive description are designated with the same reference numerals,
`film to selective etching through a photolithography tech- and explanations thereof, thus will not be repeatedly
`nique, a second film forming step of forming a second described.
`light-transmi壮ingconductive film on the substrate, which General Structure
`coats the first light-transmitting pa恥 medconductive film, 5 FIG. 1 is a plan view schematically illustrating a liquid
`and a second pattern step of providing a second light trans-
`crystal display device according to an embodiment of the
`mitting patterned conductive film on the first light-trans-
`mitting patterned conductive film in self-alignment by sub- present invention. In the following description, the present
`jecting at least the second light-transmitting conductive invention is applied to the liquid crystal display device. How-
`film to wet etching.
`. .
`10 ever, it may be applied to other display devices such as an
`The present invention provides the light-transm1ttmg con- organic EL display device without limitation. Codes X and Y
`ductive film with reduced electric resistance without increas- denote X-axis and下二axis,respectively.
`ing process steps.
`Referring to FIG. 1, a liquid crystal (not shown) is inter-
`Other advantages of the prese1_1t invention will clearly posed between a first substrate SUBl and a second substrate
`appear from the following descriptmn.
`15 SUB2, which are oppositely arranged. The second substrate
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`SUB2 is designed to face the user. A backlight (not shown) is
`provided on a back surface of the first substrate SUBl. The
`FIG. 1 is a plan view schematically illustrating a structure second substrate SUB2 has an area smaller than that of the
`of a liquid crystal display device according to an embodiment first substrate SUBl so that a lower peripheral portion SD of
`of the present invention;
`20 the first substrate SUBl is exposed. A semiconductor device
`FIG. 2 is a view illustrating a structure of a pixel in a liquid (chip) SEC is built in the lower peripheral portion SD of the
`crystal display device according to an embodiment of the first substrate SUBl. The semiconductor device SEC serves
`present invention;
`as a control circuit for driving respective pixels in a display
`FIG. 3 is a sectional view taken along line B-B shown in region AR to be described later.A seal member SL is provided
`FIG. 2;
`25 around the second substrate SUB2, which is bonded to the
`FIG. 4 is an explanatory view showing a manufacturing first substrate SUBl. The seal member SL functions in seal-
`method of a liquid crystal display device according to an ing the liquid crystal.
`己mbodimentof the present invention;
`The region surrounded by the seal member SL is defined as
`FIG. 5 is an explanatory view showing the manufacturing the display region AR. On the surface of the display region
`method of a liquid crystal display device according to the 30 AR of the first substrate SUB 1 at the liquid crystal side, gate
`embodiment of the present invention;
`wires GL each extending along X direction are aligned in Y
`FIG. 6 is an explanatory view showing the manufacturing direction, and drain wires DL each extending along Y direc-
`method of a liquid crystal display device according to the tion are aligned inX direction. The region de自nedby adjacent
`embodiment of the present invention;
`paired gate wires GL and adjacent paired drain wires DL
`FIG. 7 is an explanatory view showing the manufacturing 35 becomes a pixel region. The display region AR includes a
`method of a liquid crystal display device according to the large number of pixels arranged in matrix therein.
`embodiment of the present invention;
`Referring to an enlarged part A indicating an equivalent
`FIG. 8 is an explanatory view representing a manufacturing circuit shown in a dotted elliptical frame, each pixel region
`method of the liquid crystal display device according to an includes a thin-film transistor TFT which is turned ON by a
`embodiment of the present invention having a wiring layer 40 signal (scan signal) from the gate wire GL, a pixel electrode
`formed of a transparent conductive film;
`PX to which a signal (video signal) is supplied from the drain
`FIG. 9 is an explanatory view representing the manufac- wire DL via the thin-film transistor TFT, and an opposite
`印 ringmethodoftheliquidcrystaldisplaydeviceaccordingto electrode CT for generating electric field between the oppo-
`the embodiment of the present invention having a wiring layer site electrode CT and the pixel electrode PX.百1eelectric field
`formed of a transparent conductive film;
`45 has a component parallel to the surface of the first substrate
`FIG. 10 is an explanatory view representing the manufac- SUBl, and the liquid crystal molecules are designed to have
`turing method of the liquid crystal display device according to the orientational state changed while being kept horizontal to
`theembodimentofthepresentinventionhavingawiringlayer the surface of the first substrate SUBl. The liquid crystal
`formed of a transparent conductive film;
`display device is referred to as transverse field type (IPS
`FIG. 11 is an explanatory view representing the manufac- so type). The opposite electrode CT is designed to receive a
`turing method of the liquid crystal display device according to reference signal with respect to the video signal via the com-
`the embodiment of the present invention having a wiring layer mon wire CL which extends parallel to the gate wires GL.
`formed of a transparent conductive film;
`The gate wires GL, the drain wires DL and the common
`FIG. 12 is an explanatory view representing the manufac- wires CL are connected to the semiconductor device SEC via
`turingmethodoftheliquidcrystaldisplaydeviceaccordingto 55 corresponding leading wires (not shown) so that the gate
`theembodimentofthepresentinventionhavingawiringlayer wires GL receive the scan signals, the drain signals DL
`formed of a transparent conductive film; and
`receive the video signals, and the common wires CL receive
`FIG. 13 is a view illustrating an electric field distribution the reference signals, respectively.
`The aforementioned struc印 reis shown by taking the liquid
`for driving the liquid crystal between a pixel electrode and an
`opposite electrode of the liquid crystal display device accord- 60 crystal display device of so called transverse field type as the
`ing to the embodiment of the present invention.
`example. However, the present invention may be applied to
`the liquid crystal display device of longitudinal type, for
`example, TN (Twisted Nematic), VA (Vertical Alignment)
`and the like.
`65 Pixel Structure
`FIG. 2 illustrates the pixel structure of the liquid crystal
`An embodiment of the present invention will be described
`referring to the drawings. The same components in the display device according to an embodiment of the present
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`9
`
`

`

`US 8,409,891 B2
`
`5
`6
`invention as a plan view co汀 espondingto the part A shown in nating the protective film formed of an inorganic insulating
`FIG. 1. FIG. 3 is a sectional view taken along line B-B shown film and a protective film (planarized film) formed of an
`in FIG. 2.
`organic insulating film.
`Referring to FIG. 2, a surface of the first substrate SUBl at
`A first light-transmission patterned conductive film PXl
`the liquid crystal side, that is, a main surface of the first s formed by pa恥 m etching the light-transmitting conductive
`substrate SUBl (see FIG. 3) has a base layer GRL (see FIG. film through selective etching with a known photo lithography
`3) formed thereon.百1egate wires GL each extending along technique is formed on the surface of the protective film PAS.
`the X direction are aligned in Y direction on the upper surface A second light-transmitting patterned conductive film PX2
`of the base layer. Rectangular regions each as the pixel region which coats the liquid crystal side surface (upper surface) and
`are defined by those gate wires GL and the drain wires DL 10 the side surface of the first light-transmitting pa壮emedcon-
`each extending along the Y direction which are aligned in the ductive film PXl is formed. The pixel electrode PX is formed
`X direction. The gate wire GL is provided with a gate elec- of the first light-transmitting patterned conductive film PXl
`trade GT formed as a protrusion projecting toward the pixel and the second light-transmitting patterned conductive film
`region. The gate electrode GT serves as a gate electrode for PX2. The second light-transmitting pa壮ernedconductive film
`the thin-film transistor TFT.
`15 PX2 is configured to coat the exposed surface of the first
`Referring to FIG. 3, an insulating film GI which coats the light-transmitting patterned conductive film PXl including
`gate wire GL (gate electrode GT) is formed on the surface of its side wall surface. Each of the first light-transmitting pat-
`the first substrate SUBl on which the gate wires GL are terned conductive film PXl and the second light-transmitting
`formed. The insulating film GT functions as a gate insulating patterned conductive film PX2 is formed of a crystallized
`film in the region for forming the thin-film transistor TFT. 20 light-transmitting conductive film as d脱 出edbelow.
`The semiconductor layer (i layer) PS provided while super-
`In the embodiment, the opposite electrode CT is formed of
`imposed with the gate electrode GT in the region for forming the light-transmitting conductive film such as ITO (Indium
`the thin-film transistor TFT on the surface of the insulating Tin Oxide) ovぽ anentire area of the display region AR. A
`film GI is formed of a low temperature polysilicon (poly-Si) signal肘ferencesignal) as a reference with respect to the
`material. Low concentration impurity layers (LDD layer, 25 video signal is supplied to the opposite electrode CT so that
`n layer) LDD doped with n-type impurity at low concentra- the signals are commonly supplied to the respective pixels.
`tion are provided at the side of the drain electrode DT and the The opposite electrode CT is formed by directly laminating
`source electrode ST of the semiconductor layer PS while the common signal wires CL each formed of metal with low
`interposing the semiconductor layer PS. The low concentra- electric resistance so that the reference signal is supplied to
`tion impurity layer LDD provides the effect of mitigating 30 the opposite electrode CT via the common signal wire CL.
`field focusing between the semiconductor layer PS and the The common signal wire CL is formed adjacent or partially
`gate electrode GT. Contact layers CNL connected to the superimposed to the gate signal wire GL along the running
`source electrode ST or the drain electrode DT are provided at direction thereof while avoiding substantial pixel region. The
`the side of the drain electrode DT and the source electrode ST present invention is also applicable to the liquid crystal dis-
`of the low concentration impurity layer LDD. The contact 35 play device ofVA type or TN type having the opposite elec-
`layer CNL is a high concentration impurity layer (n+ layer) trode CT formed on the second substrate SUB2.
`doped with high concentration n-type impurity.百1econtact Pixel Producing Method 1
`layer CNL provides the effect of reducing the connection
`FIGS. 4 to 7 are explanatory views with respect to the
`resistance between the source electrode ST or the drain elec- manufacturing method of the liquid crystal display device
`trode DT, and the channel region. The thin-film transistor TFT 40 according to the embodiment of the present invention. The
`does not need to be limited to the coplanar type, but may be of method for producing the pixel electrode using the light-
`staggered type. The gate electrode does not need to be limited transmitting patterned conductive film according to the
`present invention will be described. The present invention is
`to bo壮omtype, but may be of top gate type.
`A first insulating layer INl for coating the semiconductor not limited to the pixel electrode, but may be applied to the
`layer PS, the low concentration impurity layers LDD and the 45 drain wire DL and the gate wire GL each formed of the metal
`contact layers CNL is formed on the upper surface of the first thin film to cope with high sheet resistance of the generally
`substrate SUBl. A second insulating film IN2 is further employed liquid crystal display device, the leading wiring for
`formed on the upper surface of the first insulating film INl. connecting those drain wire DL and gate wire GL to outputs
`Through holes ( contact holes) which reach the contact layers of the semiconductor device SEC, and further to the electrode
`CNL for interposing the semiconductor layer PS are formed so of the thin film transistor for forming the peripheral circuit.
`in the first insulating film INl and the second insulating film The manufacturing method according to the present invention
`IN2. The drain electrode DT and the source electrode ST are is the same as that for manufacturing the generally employed
`formed in the through hole for providing the thin-film tran- display device except the process of producing the pixel elec-
`sistor TFT. The drain wire DL (not shown) formed of, for trode formed of the light-transmitting patterned conductive
`example an aluminum thin film, is provided on the upper 55 白lm.So the method for producing the pixel electrode formed
`surface of the second insulating film IN2. The drain wire DL of the light-transmi壮ingpa社emedconductive film will be
`is electrically coupled with the drain electrode DT. The drain described in detail.
`wire DL, the gate wire GL and the gate electrode GT may be
`In the process of forming the pixel electrode PX according
`formed ofITO film to be described later.
`to the embodiment, the ITO for forming the pixel electrode
`A protective film PAS which coats the drain electrode DT, 60 PX is subjected to pa壮emetching using the known photoli-
`the source electrode ST and the drain wires DL, and pla- thography technique to obtain the first light-transmitting pat-
`narizes the surface of the first substrate SUB 1 is formed on the terned conductive film PXl, as shown in FIG. 4. In the process
`upper layer of the second insulating film IN2.百1eprotective of forming the first light-transmitting patterned conductive
`film PAS serves to avoid direct contact with the thin-film filmPXl, theITOfilmITOisformedonthesurfaceofthefirst
`transistor TFT, and prevents deterioration in characteristic of 65 substrate SUBl at the liquid crystal side, that is, the upper
`the thin-film transistor TFT. The protective film PAS has, for layer of the protective film PAS, and then the etching pa壮em
`example a double layer structure, as a body formed by lami- is formed on the upper surface of the ITO film ITO. For
`
`10
`
`

`

`US 8,409,891 B2
`
`7
`8
`example, the first light-transmitting patterned conductive film 12. In the following description, the wiring layer is formed on
`PXl along the shape of the pixel electrode PX is formed the upper surface of the first substrate SUBl. However, the
`through wet etching using chemical solution of oxalic acid. wiring layer may be formed on the upper layer of the second
`After the etching, the first light-transmitting patterned con- insulating film as the other insulating layer likewise produc-
`ductivefilmPXlisinnon-crystalline(amorphous)state.Itis 5 tion of the pixel electrode PX. In the explanation to be
`then subjected to the heat treatment such as the known anneal- described below, a three-layer light-transmitting patterned
`ing treatment to crystallize the etched first light-transmitting conductive film is formed to significantly reduce the electric
`patterned conductive film PXl.
`resistance of the wiring layer. Like the pixel electrode PX, the
`Referring to FIG. 5, the ITO film ITO as the light-trans- light-transmitting pa壮ernedconductive film is not limited to
`mi壮ingconductive film is formed on the liquid-crystal side 10 the three-layer configuration so long as two or more layers are
`surface of the first substrate SUBl, that is, the upper layer of used.
`the protective film PAS including the upper layer of the first
`After forming the ITO film on the upper surface (liquid
`light-transmitting patterned conductive film PXl. If the ITO crystal side) of the first substrate SUBl, and the wiring mask
`film ITO is formed to have the thickness equal to or larger than pattern is formed so that the ITO film is wet etched using the
`the predetermined value, the ITO film in contact with both the 15 chemical solution of oxalic acid. The ITO film IT02 in non-
`upper and side surfaces of the first light-transmitting pat- crystallized state is formed through the etching as shown in
`terned conductive film PXl, that is, the exposed surface of the FIG. 8. Therea武er,the ITO film IT02 in the non-crystallized
`first light-transmitting patterned conductive film PXl is state is subjected to the heat treatment such as annealing
`brought into the ITO film ITOl under the reaction heat in the tr回 tmentto form a first light-transmitting patterned conduc-
`crystallized state.
`20 tive film IT03 as the crystallized ITO film.
`Intheembodiment,theITOfilmITOissubjectedtothewet
`Referring to FIG. 9, the ITO film ITO is formed on the
`etching again using the chemical solution of oxalic acid. The surface of the first substrate SUBl so that the film thickness
`chemical solution of oxalic acid serves to etch only the ITO becomes equal to or larger than the predetermined value.
`film ITO in the non-crystallized state. As a result, the ITO film Under the reaction heat generated in the自lm-forming process
`ITOl in the crystallized state is kept un-etched as illustrated 25 step, the ITO film ITO around the crystallized first light-
`in FIG. 7. As clearly shown in FIG. 7, the second light- transmitting patterned conductive film IT03 is brought into
`transmitting patterned conductive film PX2 along the shape the crystallized ITO film ITOl as shown in FIG. 10.
`of the upper and side surfaces of the first light-transmitting
`The ITO film ITO is subjected to the wet etching using the
`patterned conductive film PXl is formed in self-aligmnent, chemical solution of oxalic acid so that a second li悼t-trans-
`thus defining the pixel electrode PX. The pixel electrode PX 30 mitting patterned conductive film IT04 as the crystallized
`is formed by laminating the second light-transmitting pat- ITO film is formed. The second light-transmitting patterned
`terned conductive film PX2 on the first light-transmitting conductive film ITO 4 is the light-transmitting patterned con-
`patterned conductive film PXl, and the resultant thickness is ductive自lmhaving only the crystallized ITO film ITOl kept
`larger than that of the generally employed pixel electrode PX. un-etched as shown in FIG. 10. The second light-transmi壮ing
`This makes it possible to reduce the electric resistance of the 35 patterned conductive film IT04 may be formed in self-align-
`transparent conductive film for forming the pixel electrode ment along the shape of the upper and side surfaces of the first
`PX. Reduction of the electric resistance of the pixel electrode light-transmitting patterned conductive film IT03 without
`PX makes the field distribution within the pixel electrode PX using the photo lithography technique.
`uniform, thus further making distribution of electric field E
`The ITO film is formed on the upper surface of the first
`for driving the liquid crystal between the pixel electrode PX 40 substrate SUBl that contains the second light-transmitting
`and the opposite electrode CT uniform as shown in FIG. 13. patterned conductive film IT04 again so that the upper and
`As a result, brightness difference in the same pixel may be the side surfaces of the second light-transmi壮ingpatterned
`significantly reduced. Reduction of the brightness difference conductive film IT04 are crystallized under the reaction heat
`in the same pixel is especially effective for the reduced gap as described above. The ITO film is subjected to the wet
`between electrodes accompanied with hi以1-definitionof the 45 etching using the chemical solution of oxalic acid to etch the
`liquid crystal display device. Tl山 isusable as the electrode of non-crystallized ITO film ITO. This makes it possible to form
`isotropic crystal demanded by the transverse electric field a third light-transmitting pa壮ernedconductive film ITOS in
`type.
`crystallized state in self-alignment. In this way, the wiring
`In the case where the ITO film ITO formed on the upper layer is formed of a three-layer light-transmitting patterned
`layer of the first light-transmitting patterned conductive film so conductive film including IT03, IT04 and ITOS. The result-
`PXl has the thickness equal to or smaller than the predeter- ant wiring layer is capable of reducing the electric resistance
`mined value, crystallization under the reaction heat resulting to the degree greater than the wiring layer formed of a single
`from the film-forming proc出 doesnot occur.百1eITO film layer of the light-tr出1smi壮ingpatterned conductive film.
`ITOl is thus kept non-crystallized. In this case, the crystal-
`As described above, in the liquid crystal display device
`lized ITO film ITO may be formed through annealing treat- 55 accordingtotheembodimentofthepresentinvention, the first
`ment using a laser beam, for example. The wet etching using light-transmitting patterned conductive film is