CN1609689A - Reflective and semi-transmission type liquid crystal display device and producing method thereof - Google Patents

Reflective and semi-transmission type liquid crystal display device and producing method thereof Download PDF

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CN1609689A
CN1609689A CNA2004100841709A CN200410084170A CN1609689A CN 1609689 A CN1609689 A CN 1609689A CN A2004100841709 A CNA2004100841709 A CN A2004100841709A CN 200410084170 A CN200410084170 A CN 200410084170A CN 1609689 A CN1609689 A CN 1609689A
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film
forming
alnd
thin film
liquid crystal
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CN100421014C (en
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宮本贤一
松井泰志
日野辉重
石贺展昭
吉田卓司
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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    • 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
    • G02F1/136286—Wiring, e.g. gate line, drain line
    • 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
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133553—Reflecting elements
    • 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
    • G02F1/136227—Through-hole connection of the pixel electrode to the active element through an insulation layer
    • 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
    • G02F1/136286—Wiring, e.g. gate line, drain line
    • G02F1/136295—Materials; Compositions; Manufacture processes

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Liquid Crystal (AREA)

Abstract

To improve manufacturing yield of reflection-type and semi-transparent liquid crystal display panels, having low resistance of wiring and superior display characteristics by superior reflective characteristics, and to provide a manufacturing method which can simplify the process. The method for manufacturing the reflective liquid crystal display includes at least a first step for forming gate wiring consisting of a first metal thin film and a gate electrode on a transparent insulation substrate; a second step for forming a semiconductor layer; a third step for forming source wiring consisting of a second metal thin film, a source electrode, a drain electrode, and a channel part of a thin film transistor; a fourth step for forming an interlayer insulation film, and for forming a recessed and protruded configuration on the surface of a pixel electrode part and a contact hole; and a fifth step for depositing a third metal thin film and for forming a pixel electrode. The first metal thin film is a dual-layer film, consisting of an AlNd film and another AlNd film formed on the upper layer of the AlNd film, wherein at least one element among nitrogen, carbon, and oxygen is added thereto.

Description

Reflection-type and semi-transmission-type liquid crystal display device and method for manufacturing the same
Technical Field
The present invention relates to a method for manufacturing a thin film transistor array substrate for a liquid crystal display device, which can be used as a reflective type or a transflective type that can be used as both a reflective type and a transmissive type.
Background
Liquid crystal display panels have the advantages of being thin and low in power consumption, and thus are widely used in OA devices such as word processors and personal computers, portable information devices such as electronic notebooks, camera-integrated VTRs including liquid crystal monitors, and the like.
In contrast to CRT (cathode ray tube) or EL (electroluminescence) display, a liquid crystal display panel mounted on the liquid crystal display panel is often a so-called transmissive liquid crystal display panel in which an image is displayed by controlling the amount of transmission of a backlight by using a liquid crystal display panel, because the liquid crystal display panel does not emit light by itself and is provided with a fluorescent tube called a backlight on the back surface or side surface.
However, in the transmissive liquid crystal display panel, the backlight normally occupies 50% or more of the total power consumption of the liquid crystal display panel, and therefore the power consumption is increased by the provision of the backlight.
In contrast to the reflective liquid crystal display panel, the transmissive liquid crystal display panel emits dark display light compared to ambient light when the ambient light is very bright, and thus the display is difficult to recognize.
Therefore, unlike the transmissive liquid crystal display panel, in portable information devices which are frequently used outdoors or carried in many cases, a reflective liquid crystal display panel is used in which a reflective plate is provided on one substrate instead of a backlight and ambient light is reflected by the surface of the reflective plate to perform display, and is disclosed in, for example, japanese unexamined patent application publication No. h 6-175126, fig. 1 and fig. 2.
However, the reflective liquid crystal display panel using the reflected light of the ambient light has a disadvantage that visibility is greatly reduced when the ambient light is dark.
In order to solve such a problem of the reflective liquid crystal display panel, a structure for realizing both of the transmissive display and the reflective display by one liquid crystal display panel by using a transflective film which transmits a part of the backlight and reflects a part of the ambient light is disclosed in, for example, fig. 1 and 2 of japanese unexamined patent application publication No. h 11-101992.
In conventional reflective and transflective liquid crystal display panels, a material having a high reflectance such as silver or aluminum is used as areflective electrode, and Al is often used because of its superiority in terms of cost, corrosion, and other processing properties.
In the transflective liquid crystal display panel, a transparent conductive film such as ITO made of indium oxide, tin oxide, or the like is generally used as a transmissive electrode. On the other hand, although the reflective liquid crystal display panel does not have a transmissive electrode, for example, in a wiring for transmitting a scanning signal, a video signal, or the like and a connection terminal portion of a liquid crystal driving driver IC, a transparent electrode pad such as ITO is used in order to prevent high resistance due to oxidation of the connection portion caused by a post process, a working environment, or the like.
When Al as a reflective electrode is formed and patterned in a liquid crystal display panel having such a transparent electrode pattern and terminal pad pattern made of ITO, as disclosed in, for example, Japanese patent laid-open Nos. 11-281993 and 2003-50389, a cell reaction occurs between ITO and Al as electrodes in an organic alkali developer used for resist patterning at the time of Al film patterning, and there is a problem that oxidation corrosion of Al and reduction corrosion of ITO occur, and a defect such as disconnection defect and reduction of transmittance of a transmissive electrode portion occurs.
For the purpose of suppressing the cell reaction between ITO and Al, for example, the following methods can be used if the inventions disclosed in JP-A-4-293021 and JP-A-8-62628 are referred to: chromium or molybdenum is formed in an upper layer of an Al metal of the reflective electrode to suppress a cell reaction in a developer during resist patterning, and Cr or Mo of the upper layer is entirely removed after the reflective electrode pattern is formed to form the Al reflective electrode. However, this method has a problem that the Al surface is damaged and the reflectance is lowered when a known cerium ammonium nitrate + perchloric acid-based etching solution is used to remove Cr over the entire surface. On the other hand, in a known phosphoric acid + nitric acid + acetic acid-based etching solution used for removing Mo from the entire surface, Al itself in the lower layer is also etched, and there is a problem that it is difficult to form a reflective electrode. Therefore, it is necessary to devise a new method for suppressing the battery reaction without forming Cr or Mo in the composition of the Al metal used for the reflective electrode or in the upper layer of the Al surface.
In the case of using Al having low resistance as a wiring material of conventional reflective and transflective liquid crystal display panels, there is a problem that the ITO/Al interface contact resistance is increased and the signal current in the terminal portion is substantially cut off due to the diffusion of Al and ITO interface in the terminal connection portion to form an Al oxide layer in addition to the above-described cell reaction.
For example, Mo is considered as a material for improving contact resistance with ITO and reducing resistance of wiring, but Mo is insufficient in moisture resistance and chemical resistance, and is likely to cause corrosion in a terminal portion, for example, and thus has a problem in reliability. On the other hand, when a wiring terminal portion is formed by forming a contact hole in an insulating film made of silicon nitride (SiN) by known dry etching using fluorine gas, Mo is simultaneously etched during the dry etching, and thus there is a problem that the wiring terminal portion cannot be formed, and there is a need for devising the composition of Mo metal, and the like.
Disclosure of Invention
The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a manufacturing method capable of improving the manufacturing yield of a reflective type and a transflective type liquid crystal display panel having good display characteristics due to low resistance wiring and excellent reflection characteristics, and simplifying the process.
The method of manufacturing a reflective liquid crystal display device according to claim 1 of the present invention at least includes: a first step of forming a first metal thin film on a transparent insulating substrate and forming a gate wiring and a gate electrode by using a first photolithography process; a second step of forming a gate insulating film, a semiconductor active film, and an ohmic contact film in this order and forming a semiconductor layer by a second photolithography process; a third step of forming a second metal thin film and forming a source wiring, a source electrode, a drain electrode, and a channel portion of the thin film transistor by using a third photolithography process; a fourth step of forming an interlayer insulating film and forming a concave-convex shape on the surface of the pixel electrode portion and contact holes reaching the gate wiring terminal portion, the source wiring terminal portion, and the drain electrode by using a fourth photolithography process; and a fifth step of forming a third metal thin film and forming a pixel electrode by using a fifth photolithography process, wherein the first metal thin film is a double-layer film including an AlNd film and an AlNd film formed on the AlNd film and to which at least one element selected from nitrogen, carbon, and oxygen is added.
The first metal thin film is preferably an alloy in which Mo is added with Nb.
The second metal film is preferably a MoNb or MoNb/AlNd/MoNb three-layer film.
Preferably, the third metal thin film is formed by forming and patterning a three-layer film of Cr/AlNd/Cr, and then removing the upper Cr layer.
The third metal film is preferably a double-layer film of AlCu/MoNb or AlNd/MoNb.
The method of manufacturing a transflective liquid crystal display device according to claim 2 of the present invention at least includes: a first step of forming a first metal thin film on a transparent insulating substrate, and forming a gate wiring and a gate electrode by using a first photolithography process; a second step of forming a gate insulating film, a semiconductor active film, and an ohmic contact film in this order and forming a semiconductor layer by a second photolithography process; a third step of forming a second metal thin film and forming a source wiring, a source electrode, a drain electrode, and a channel portion of the thin film transistor by using a third photolithography process; a fourth step of forming an interlayer insulating film and forming a concave-convex shape on the surface of the pixel electrode portion, an opening portion of the pixel transmission electrode portion, and contact holes reaching the gate wiring terminal portion, the source wiring terminal portion, and the drain electrode by using a fourth photolithography process; a fifth step of forming a transparent conductive film and forming a transmissive pixel electrode and a terminal pad by using a fifth photolithography process; and a sixth step of forming a third metal thin film and forming a reflective pixel electrode by using a sixth photolithography process, wherein the first metal thin film is a double-layer film including an AlNd film and an AlNd film formed on the AlNd film and to which at least one element selected from nitrogen, carbon, and oxygen is added.
The first metal thin film is preferably an alloy in which Mo is added with Nb.
The second metal film is preferably a MoNb or MoNb/AlNd/MoNb three-layer film.
Preferably, the third metal thin film is formed by forming and patterning a three-layer film of Cr/AlNd/Cr, and then removing the upper Cr layer.
The third metal film is preferably a double-layer film of AlCu/MoNb or AlNd/MoNb.
According to the present invention, since the gate wiring resistance and the source wiring resistance can be reduced, the contact resistance between the terminal pad ITO film and the pixel ITO film and the gate wiring, the source wiring, and the drain electrode can be reduced, and the pixel reflective film having a good reflective characteristic with little process damage can be formed, a reflective type and a transflective type liquid crystal display device having a bright and high-quality display characteristic without causing display defects such as dot defect defects and display irregularities can be manufactured with high productivity.
Drawings
FIG. 1 is a plan view showing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
FIG. 2 is a cross-sectional view showing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
Fig. 3 is a view showing a process for manufacturing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
Fig. 4 is a view showing a process for manufacturing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
Fig. 5 is a view showing a process for manufacturing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
Fig. 6 is a view showing a process for manufacturing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
Fig. 7 is a view showing a process for manufacturing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
Fig. 8 is a view showing a process for manufacturing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
Fig. 9 is a view showing a process for manufacturing a TFT array substrate for a reflective liquid crystal display device according to embodiments 1 to 5 of the present invention.
FIG. 10 is a graph showing reflectance characteristics in the case of using an Al-0.2 wt% Cu reflective film as a comparative example of the reflective type and transflective type liquid crystal display devices according to embodiments 1 to 6 of the present invention.
Fig. 11 is a graph showing reflectance characteristics in the case of using an Al-1.0 wt% Nd reflective film as an embodiment of the reflective type and transflective type liquid crystal display devices according to embodiments 1 to 6 of the present invention.
Fig. 12 is a plan view showing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 13 is a sectional view showing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 14 is a view showing a process for manufacturing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 15 is a view showing a process for manufacturing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 16 is a diagram showing a process for manufacturing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 17 is a diagram showing a process for manufacturing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 18 is a view showing a process for manufacturing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 19 is a diagram showing a process for manufacturing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 20 is a view showing a process for manufacturing a TFT array substrate for a transflective liquid crystal display device according to embodiment 6 of the present invention.
Fig. 21 is a graph showing reflectance characteristics in the case where a polyimide film for controlling liquid crystal alignment is formed on a pure Al reflective film in the reflective type and transflective type liquid crystal display devices according to embodiments 1 to 6 of the present invention.
Fig. 22 is a graph showing reflectance characteristics in the case where a polyimide film for controlling liquid crystal alignment is formed on an Al-0.2 wt% Cu reflective film in the reflective type and transflective type liquid crystal display devices according to embodiments 1 to 6 of the present invention.
Fig. 23 is a graph showing reflectance characteristics in the case where a polyimide film for controlling liquid crystal alignment is formed on an Al-1 wt% Nd reflective film in the reflective and transflective liquid crystal display devices according to embodiments 1 to 6 of the present invention.
Fig. 24 is an explanatory diagram conceptually showing a reduction mechanism of ITO in the case of an upper Al/lower Cr bilayer film with respect to an electrochemical reaction (cell reaction) of an Al film and an ITO film.
Fig. 25 is an explanatory diagram conceptually showing a reduction mechanism of ITO in the case of an upper Al/lower Mo bilayer film with respect to an electrochemical reaction (cell reaction) of an Al film and an ITO film.
Detailed Description
Embodiment mode 1
A method for manufacturing a reflective liquid crystal display device according to embodiment 1 of the present invention will be described below with reference to the drawings. Fig. 1 is a plan view showing a reflective liquid crystal display device according to embodiment 1 of the present invention, fig. 2 is a cross-sectional view, and fig. 3 to 9 are process diagrams. In fig. 1, a plurality of concave portions 35a of the reflective pixel electrode are provided in the area of the reflective pixel electrode 35, and a concave-convex shape is formed.
First, a first metal thin film is formed on a transparent insulating substrate 1 such as a glass substrate, and a gate electrode 2, an auxiliary capacitor electrode 3, a gate wiring 4, and a gateterminal portion 5 are formed in a first photolithography step (see fig. 3).
In the present embodiment, an AlNd alloy in which 0.8 to 5 wt% of Nd is added to Al and which has a thickness of 200nm is formed by a known sputtering method using Ar gas. The sputtering condition is that the film-forming power density is 3W/cm under the DC magnetron sputtering mode2And the flow rate of Ar gas is 40 sccm. Then, N was mixed with Ar gas in accordance with a known method2A reactive sputtering method using a gaseous atmosphere was used to form an AlNd-N film to which nitrogen atoms were added in a thickness of 50 nm. The sputtering condition is that the film forming power density is 3W/cm2Ar gas flow rate 40sccm, N2The gas flow rate was 20 sccm. Through the above, a two-layer film having an AlNd film with a thickness of 200nm and an AlNd — N film with a thickness of 50nm as an upper layer thereof was formed. In this case, the composition of the N element in the AlNd — N film was about 18 wt%. Then, the double-layer film is collectively etched with a known solution containing phosphoric acid + nitric acid + acetic acid, and then the resist pattern is removed, thereby forming patterns of 2 to 5 such as the gate electrode.
Next, the first insulating film 6, the semiconductor film 7, and the ohmic contact film 8 are sequentially formed, and a semiconductor pattern including the semiconductor film 7 and the ohmic contact film 8 is formed in the 2 nd photolithography step (see fig. 4).
In this embodiment mode, 400nm SiN as the first insulating film 6, 150nm a-Si as the semiconductor film 7, and 30nm n are sequentially formed by a Chemical Vapor Deposition (CVD) method+a-Si is used as the ohmic contact film 8, and a semiconductor pattern is formed by a dry etching method using a fluorine-based gas.
Next, a second metal thin film is formed,and a source electrode 9, a drain electrode 10, a source wiring 11, and a source terminal portion 12 are formed in a third photolithography step (see fig. 5).
In the present embodiment, a MoNb alloy in which 2.5 to 20 wt% of Nb is added to Mo is formed into a film with a thickness of 200nm by a sputtering method, and etched with a known solution containing phosphoric acid + nitric acid + acetic acid to form 9 to 12 patterns of the source electrode and the like.
Next, the second insulating film 13 is formed, and then the interlayer insulating film 14 made of a photosensitive organic resin film is applied and formed, and in the fourth photolithography step, the uneven shape 15, the first contact hole 17 penetrating the terminal surface of the drain electrode 10 made of the second metal film, the contact hole 18 penetrating the terminal surface of the gate terminal portion 5 made of the first metal film, and the contact hole 19 penetrating the terminal surface of the source terminal portion 12 made of the second metal film are formed on the pixel reflection portion of the interlayer insulating film (see fig. 6).
In this embodiment, 100nm of SiN is formed as the second insulating film 13, and subsequently, a JSR PC335 is coated by spin coating to a film thickness of 3.2 to 3.9 μm to form the photosensitive organic resin film 14. Then, a first exposure is performed using a photomask having the contact holes 17, 18, 19, a second exposure is performed using a photomask having the concave-convex reflective portion pattern 15 at an exposure amount of 20 to 40% of the first exposure amount, and then the concave-convex reflective portion pattern 15 and the contact holes 17, 18, 19 are formed by developing with an organic alkali developer.
Next, a transparent conductive film is formed, and in the fifth photoengraving step, a gate terminal pad 21 connected to the gate terminal portion 5 is formed through the contact hole 18, and a source terminal pad 22 connected to the source terminal portion 12 is formed through the contact hole 19 (see fig. 7).
In this embodiment, ITO is formed as a transparent conductive film in a thickness of 100nm by a sputtering method, and etching is performed using a solution containing hydrochloric acid + nitric acid to form the gate terminal pad 21 and the source terminal pad 22.
Next, a third metal thin film having high reflection characteristics is formed, and the reflective pixel electrode 35 is formed in a sixth photolithography step. After the lowermost layer film 23, the reflective film 24, and the uppermost layer film 25 are formed, the uppermost layer film 25 is etched away to form the reflective pixel electrode 35 (see fig. 8 and 9).
In this embodiment, a Cr/AlNd/Cr triple layer film is formed by forming Cr23 as a third metal thin film with a thickness of 100nm by sputtering, then forming an AlNd alloy 24 with 0.5 to 3 wt% of Nd added to Al as an upper layer with a thickness of 300nm, and then forming Cr25 with a thickness of 100 nm. Next, after patterning the resist by the sixth photolithography step, Cr25 in the uppermost layer was etched using a known solution containing cerium ammonium nitrate + perchloric acid, the AlNd alloy 24 in the second layer was etched using a known solution containing phosphoric acid + nitric acid + acetic acid, and Cr23 in the lowermost layer was etched again using a solution containing cerium ammonium nitrate + perchloric acid (see fig. 8).
In the present embodiment, the lowermost Cr23 layer of the third metal thin film is formed as a barrier layer for preventing a step disconnection defect of the AlNd film 24 on the bottom surface of the pixel drain contact hole 17 and preventing the AlNd film 24 from being directly formed on the ITO films of the gate terminal pad 21 and the source terminal pad 22. If the AlNd film 24 is directly formed on the ITO film without forming the lowermost Cr23 layer, an AlOx reaction layer is formed on the ITO/AlNd interface, and therefore, even after the third metal thin film is removed by etching, damage remains on the surfaces of the terminal pads ITO21 and 22, and the terminal resistance increases, which causes display defects. On the other hand, the uppermost layer Cr25 is a barrier layer for preventing corrosion of the terminal pads 21 and 22 due to a battery reaction between Al and the underlying ITO in a developer during resist patterning in a photolithography step.
Finally, after etching the Cr/AlNd/Cr triple-layer film as the third metal thin film, and removing the resist pattern, Cr25 as the uppermost layer was etched all over using a solution containing ammonium cerium nitrate and perchloric acid to expose the surface of the AlNd film 24, thereby forming reflective pixel electrode patterns 35(23, 24) (see fig. 9).
An alignment control film for aligning liquid crystal is formed on the TFT array substrate for a liquid crystal display device manufactured through the above steps by using a known technique, a color filter for performing color display, a black matrix (black matrix), and a counter substrate on which a counter electrode and an alignment control film are formed are bonded by using a known technique, and liquid crystal is injected between the TFT array substrate and the counter substrate, thereby completing the reflective liquid crystal display device according to embodiment 1 of the present invention.
In the reflective liquid crystal display device thus completed, an AlNd alloy in which 0.8 to 5 wt% of Nd is added to Al is used as the first metal thin film, so that it is possible to prevent the surface roughness of protrusions and recesses, which is generally called hillocks (hillocks), from occurring on the thin film surface, and to suppress the wiring resistance of the gate electrode to be lower than that in the case of using a conventional Cr thin film, as shown in table 1.
Table 1 device structures and electrical characteristics of embodiment and comparative examples
Comparative example 1 Comparative example 2 Embodiment mode 1 Embodiment mode 2 Embodiment 3 Embodiment 4 Embodiment 5
Device for cleaning the skin Piece Knot Structure of the organization First metal film (grid cloth)Wire) Second metal film (Source wiring) Through pixel electrode/terminal pad film Cr Cr ITO Al Cr ITO AlNdN/AlNd MoNb ITO MoNb MoNd ITO AlNdN/AlNd MoNb/AlNd /MoNb ITO MoNb MoNb/AlNd /MoNb ITO MoNb/AlNd MoNb/AlNd /MoNb ITO
Electric power Specially for treating diabetes Property of (2) Grid wiring resistance (to Cr) 1 0.2 0.2 0.6 0.2 0.6 0.2
Source wiring resistance (to Cr) 1 1 0.6 0.6 0.2 0.2 0.2
ITO/grid wiring contact resistance (to Cr) 1 1000000 1 0.4 1 0.4 0.4
ITO/source wiring contact resistance (to Cr) 1 1 0.4 0.4 0.4 0.4 0.4
In this case, if the Nd component added to Al is less than 0.8 wt%, the hillock suppressing effect is reduced, which is not desirable. On the other hand, if it exceeds 5% by weight, it is not preferable because it is difficult to control the wiring width with high accuracy due to an increase in wiring resistance and an increase in the amount of edge corrosion of the wiring pattern during wet etching. In the present embodiment, by forming an AlNd — N film to which N atoms are added on the upper layer of the AlNd film, the contact resistance values of the gate terminal ITO pad 21 of the gate terminal portion and the gate terminal portion 5 can be reduced as compared with the conventional case of only an AlNd thin film, and etching can be performed in one wet etching, so that the process can be simplified. Therefore, compared with the case of using Cr wiring in the conventional example, the margin against display unevenness due to signal delay caused by an increase in wiring resistance can be increased, and a reflective liquid crystal display device having high display quality can be obtained.
The content of N in the AlNd — N film used in the present embodiment is about 18 wt%, but the present invention is not limited thereto, and the effect of the present invention can be obtained if the content of N is in the range of 5 wt% to 25 wt%. Further, not limited to nitrogen, an AlNd-C film or an AlNd-O film to which carbon or oxygen is added may be used.
Further, since the second metal thin film is made of a MoNb alloy in which 2.5 to 20 wt% of Nb is added to Mo, as shown in table 1, the contact resistance with the source terminal ITO pad 22 of the source terminal portion can be reduced while the wiring resistance of the source is suppressed to be low as compared with the conventional case of using a Cr thin film, and thus, high-performance display characteristics without unevenness in display can be obtained. In this case, if the same etching solution as that for the Al — Mo thin film is used in the wet etching, the pure Mo film is etched drastically, and therefore, it is necessary to prepare a new etching solution dedicated to pure Mo. However, as in the present embodiment, since the etching rate is decreased by adding 2.5 to 20 wt% of Nb to Mo and approaches the etching rate of the AlNd thin film, the MoNb thin film can be etched at the same etching rate as the AlNd thin film, thereby avoiding the complexity of the process.
Further, since the AlNd alloy 24 in which 0.5 to 3 wt% of Nd is added to Al is used as the high-reflectance metal of the third metal thin film, it is possible to minimize a decrease in reflectance after the formation of the uppermost Cr25 layer and the removal of corrosion, as compared with a conventional Al alloy, and to obtain a reflective liquid crystal display device having bright display characteristics.
That is, as a comparative example for comparison with the present invention, as shown in fig. 10, in the case of using a conventional Al-0.2 wt% Cu alloy, the reflectance was reduced by 10% or more depending on the wavelength, compared to the case of using an Al-1.0 wt% Nd alloy in which Nd was added to Al, as shown in fig. 11 of the present embodiment, and it was found that the reflectance was not substantially reduced after both the formation and removal of Cr, when the Cr layer was formed and the blanket etching was removed. Here, although a Cr film is used as the uppermost layer, any alloy may be used instead of the Cr film as long as it can suppress a cell reaction with ITO in a resist developer and selectively corrode an Al — Nd film, and for example, Ta, W, Ti, or the like can be used.
Embodiment mode 2
Instead of the AlNd — N/AlNd double layer film as the first metal thin film in embodiment 1, a MoNb alloy film to which 2.5 to 20 weight of Nb is added is used. In the preferred embodiment, in the step of fig. 3, a MoNb alloy in which 5 wt% of Nb is added to Mo is formed as a first metal thin film in a thickness of 200nm by a known sputtering method using Ar gas, and the first metal thin film is etched by a known solution containingphosphoric acid + nitric acid + acetic acid to form the gate electrode 2, the storage capacitor electrode 3, the gate wiring 4, and the gate terminal portion 5. As the known solution containing phosphoric acid + nitric acid + acetic acid, the same solution as in the case of the AlNd — N/AlNd bilayer film of embodiment 1 can be used. Then, similarly to embodiment 1, the reflection type liquid crystal display device of embodiment 2 of the present invention is completed through the steps of fig. 4 to 9.
As shown in table 1, in the case of embodiment 2, although the gate wiring resistance is higher than that of embodiment 1, the contact resistance with the ITO film of the terminal pad is lower than that of embodiment 1, and therefore, the process margin for the display defect can be increased.
Embodiment 3
Instead of the MoNb alloy film as the second metal thin film in embodiment 1, a MoNb/AlNd/MoNb three-layer film is used. When a MoNb alloy film in which 2.5 to 20 wt% of Nb is added to Mo is used for the lowermost layer and the uppermost layer, and an AlNd alloy film in which 0.8 to 5.0 wt% of Al is added is used for the intermediate layer, a MoNb/AlNd/MoNb three-layer film can be etched together in one etching using a chemical solution containing phosphoric acid + nitric acid + acetic acid, which has been conventionally known as an Al etchant (etching solution). In this case, the three-layer film can be etched without steps between layers and with a smooth cross-sectional shape. As a preferable example, in the present embodiment, after the steps of fig. 3 to 4 are performed, as in embodiment 1, in the step of fig. 5, a MoNb alloy in which 5 wt% of Nb is added to Mo, an AlNd alloy in which 2 wt% of Nd is added to Al, and a MoNb alloy in which 5 wt% of Nb is further added to Mo are successively formed in the thickness of 50nm, 200nm, and 50nm in this order as the second metal thin film by aknown sputtering method using Ar gas, thereby forming a MoNb/AlNd/MoNb three-layer film. Then, etching is performed using a known solution containing phosphoric acid + nitric acid + acetic acid, thereby forming a source electrode 9, a drain electrode 10, a source wiring 11, and a drain wiring 12. In this case, the etched cross section of the three-layer film has a smooth shape without steps. The intermediate layer is not limited to AlNd alloy, and for example, AlCu alloy in which 0.1 to 1 wt% of Cu is added to Al may be used.
Then, the same steps as those in embodiment 1 as in fig. 6 to 9 are performed, thereby completing a reflective liquid crystal display device according to embodiment 3 of the present invention. In the case of embodiment 3, as shown in table 1, since the source wiring resistance can be reduced as compared with embodiment 1, the process margin against the display defect can be further improved.
Embodiment 4
Instead of the AlNd — N/AlNd double layer film still serving as the first metal thin film in embodiment 3, a single layer film of a MoNb alloy having a thickness of 200nm, in which 2.5 to 20 wt% of Nb is added to Mo, is used. In this case, as shown in table 1, although the gate wiring resistance is higher than that of embodiment 3, the contact resistance with the ITO film of the terminal pad is lower than that of embodiment 3, and therefore, the process margin against the display defect can be improved.
Embodiment 5
Instead of the AlNd — N/AlNd double layer film as the first metal thin film in embodiment 3, a MoNb/AlNd double layer film is used in which a MoNb containing 2.5 to 20 wt% of Nb added to Mo is laminated on an upper layer of an AlNd alloy containing 0.8 to 5 wt% of Nd added to Al. In a preferred embodiment, in the step of FIG. 3, an AlNd alloy in which 2 wt% of Nd is added to Al with a thickness of 200nm and then a MoNb alloy in which 5 wt% of Nb is added to Mo with a thickness of 50nm are successively formed by a known sputtering method using Ar gas, thereby forming a MoNb/AlNd bilayer film. Then, the MoNb/AlNd double-layer film is collectively etched using a chemical solution containing phosphoric acid + nitric acid + acetic acid, which is a known Al etchant, to form the gate electrode 2, the storage capacitor electrode 3, the gate wiring 4, and the gate terminal portion 5. As the known solution containing phosphoric acid + nitric acid + acetic acid, the same solution as in the case of the AlNd — N/AlNd bilayer film of embodiment 1 can be used. Then, the same steps as those in embodiment 1 as in fig. 4 to 9 are performed, thereby completing a reflective liquid crystal display device according to embodiment 5 of the present invention.
In this case, as shown in table 1, as compared with embodiment 1, the source wiring resistance can be reduced, and the contact resistance between the ITO film of the gate terminal pad and the gate terminal can be reduced, so that the process margin against the display defect can be increased.
Embodiment 6
A method for manufacturing a transflective liquid crystal display device according to embodiment 6 of the present invention will be described with reference to the drawings. Fig. 12 is a plan view showing a transflective liquid crystal display device according to embodiment 6 of the present invention, fig. 13 is a sectional view, and fig. 14 to 20 are process views.
First, a first metal thin film is formed on a transparent insulating substrate 1 such as a glass substrate, and a gate electrode 2, an auxiliary capacitor electrode 3, a gate wiring 4, and a gate terminal portion 5 are formed in a first photolithography step (see fig. 14).
In the present embodiment, an AlNd alloy in which 0.8 to 5 wt% of Nd is added to Al is first deposited in a thickness of 200nm by a known sputtering method using Ar gas. Under the DC magnetron sputtering mode, the sputtering condition is that the film forming power density is 3W/cm2And the flow rate of Ar gas is 40 sccm. Next, N was mixed with Ar gas as known2The gas reactive sputtering method of (2) is a method of forming an AlNd-N film to which nitrogen atoms are added in a thickness of 50 nm. The sputtering condition is that the film forming power density is 3W/cm2Ar gas flow rate 40sccm, N2The gas flow rate was 20 sccm. Through the above, a two-layer film of AlNd of 200nm thickness and an AlNd — N film having a thickness of 50nm on the upper layer thereof was formed. In this case, the N element composition of the upper AlNd — N film was about 18 wt%. Then, the double-layer film is collectively etched with a known solution containing phosphoric acid + nitric acid + acetic acid, and then the resist pattern is removed, thereby forming the patterns 2 to 5.
Next, the first insulating film 6, the semiconductor film 7, and the ohmic contact film 8 are sequentially formed, and a semiconductor pattern including the semiconductor film 7 and the ohmic contact film is formed in the second photolithography step (see fig. 15).
In this embodiment mode, 40nm SiN as the first insulating film 6, 150nm a-Si as the semiconductor film 7, and 30nm a-Si are sequentially formed by a Chemical Vapor Deposition (CVD) methodn+a-Si is used as the ohmic contact film 8, and a semiconductor pattern is formed by a dry etching method using a fluorine-based gas.
Next, a second metal thin film is formed, and the source electrode 9, the drain electrode 10, the source wiring 11, and the source terminal portion 12 are formed in a third photolithography step (see fig. 16).
In the present embodiment, a MoNb alloy in which 2.5 to 20 wt% of Nb is added to Mo of 200nm thickness is formed as a second metal thin film by sputtering, and etching is performed using a known solution containing phosphoric acid + nitric acid + acetic acid to form the patterns of 9 to 12.
Next, after the second insulating film 13 is formed, an interlayer insulating film 14 made of a photosensitive organic resin film is applied and formed, and in the fourth photolithography step, a concave-convex shape 15 and a concave pattern 16 of a pixel transmission portion, a first contact hole 17 penetrating to the terminal surface of the drain electrode 10 made of the second metal film, a contact hole 18 penetrating to the terminal surface of the gate terminal portion 5 made of the first metal film, and a contact hole 19 penetrating to the terminal surface of the source terminal portion 12 made of the second metal film are formed in the pixel reflection portion of the interlayer insulating film (see fig. 17).
In this embodiment, after 100nm of SiN is formed as a second insulating film, a JSR PC335 is coated by spin coating to a film thickness of 3.2 to 3.9 μm to form a photosensitive organic resin film. Then, the reflective portion concave-convex pattern 15, the transmissive portion concave pattern 16, and the contact holes 17, 18, and 19 are formed by performing a first exposure using a photomask having the transmissive portion pattern 16 and the contact holes 17, 18, and 19, performing a second exposure using a photomask having the reflective portion concave-convex pattern 15 at an exposure amount of 20 to 40%, and developing with an organic alkali developer.
Next, a transparent conductive film is formed, and in a fifth photoengraving step, a pixel drain contact portion 20a extending from the pixel electrode pattern 20 and connected to the drain electrode 10 via the contact hole 17, a gate terminal pad 21 connected to the gate terminalportion 5 via the contact hole 18, and a source terminal pad 22 connected to the source terminal portion 12 via the contact hole 19 are formed (see fig. 18).
In this embodiment, ITO is formed as a transparent conductive film with a thickness of 100nm by a sputtering method, and etching is performed using a solution containing hydrochloric acid + nitric acid.
Next, a third metal thin film having high reflection characteristics is formed as a second pixel electrode, and reflective pixel electrodes 35(23, 24) are formed in a sixth photolithography step (see fig. 19 and 20).
In this embodiment, Cr23 is formed as a third metal thin film of the second pixel electrode with a thickness of 100nm by sputtering, then an AlNd alloy 24 in which 0.5 to 3 wt% of Nd is added to Al is formed as an upper layer, and then Cr25 is formed with a thickness of 100nm to form a Cr/AlNd/Cr triple layer film. Next, after patterning the resist in the sixth photolithography step, Cr25 in the uppermost layer was etched using a known solution containing cerium ammonium nitrate + perchloric acid, the AlNd alloy 24 in the second layer was etched using a known solution containing phosphoric acid + nitric acid + acetic acid, and Cr23 in the lowermost layer was etched again using a solution containing cerium ammonium nitrate + perchloric acid (see fig. 19).
In the present embodiment, the lowermost Cr23 layer of the third metal thin film is a barrier layer formed to prevent a segment disconnection defect of the AlNd film 24 in the bottom surface of the pixel drain contact hole 17 and to prevent the AlNd24 from being directly formed on the ITO films of the gate terminal pad 21 and the source terminal pad 22. If AlNd24 is directly formed on the ITO surface without forming the lowermost Cr23 layer, an AlOx reaction layer is generated at the ITO/AlNd interface, and therefore, even after the third metal thin film is removed by etching, damage remains on the surfaces of the terminal pads ITO21 and 22, and the terminal resistance increases, which causes display defects. The uppermost Cr25 layer is a barrier layer for preventing corrosion of the ITO film of the first transparent pixel electrode 20 and the terminal pads 21 and 22 due to a battery reaction between Al and the underlying ITO in a developer during resist patterning in a photolithography step.
Finally, after etching the third metal thin film Cr/AlNd/Cr trilayer film and further removing the resist pattern, the uppermost Cr25 was etched entirely using a cerium ammonium nitrate + perchloric acid solution to expose the surface of the AlNd film 24, thereby forming reflective pixel electrode patterns 35(23, 24) (see fig. 20).
On the TFT array substrate for a transmissive liquid crystal display device manufactured through the above steps, an alignment control film for aligning liquid crystal is formed by using a known technique, a counter substrate on which a color filter, a black matrix, a counter electrode, and an alignment control film for color display are formed is bonded by using a known technique, and liquid crystal is injected between the TFT array substrate and the counter substrate, thereby completing the transmissive liquid crystal display device according to embodiment 6 of the present invention.
Thus, the completed transmissive liquid crystal display device uses an AlNd alloy in which 0.8 to 5 wt% of Nd is added to Al as the first metal thin film, and therefore, it is possible to prevent the surface roughness of the film surface from being raised, which is generally called hillock, and to suppress the wiring resistance of the gate electrode to be lower than that in the case of using a conventional Cr thin film, as shown in table 1. In this case, if the Nd composition added to Al is less than 0.8 wt%, the hillocksuppressing effect is reduced, which is not preferable. On the other hand, if the amount exceeds 5% by weight, it is not preferable because it is difficult to control the wiring width with high accuracy due to an increase in wiring resistance and an increase in the amount of edge corrosion of the wiring pattern during wet etching. In this embodiment, on the other hand, by forming an AlNd — N film to which N atoms are added on the upper layer of the AlNd film, the contact resistance values of the gate terminal ITO pad 21 and the gate terminal portion 5 of the gate terminal portion can be reduced as compared with the case of only the conventional AlNd thin film, and etching can be performed in one wet etching, so that the process can be simplified. Therefore, compared with the case of using Cr wiring in the conventional example, the margin of defect for display unevenness due to signal delay caused by an increase in wiring resistance can be increased, and a transmissive liquid crystal display device having high display quality can be obtained.
The content of N in the AlNd — N film used in the present embodiment is about 18 wt%, but the present invention is not limited thereto, and the effect of the present invention can be obtained if the content of N is in the range of 5 wt% to 25 wt%. Further, not limited to nitrogen, an AlNd-C film or an AlNd-O film to which carbon or oxygen is added may be used.
Further, since the second metal thin film is made of a MoNb alloy in which 2.5 to 20 wt% of Nb is added to Mo, as shown in table 1, the contact resistance with the source terminal ITO pad 22 of the source terminal portion can be reduced while the wiring resistance of the source is suppressed to be low as compared with the conventional case of using a Cr thin film, and thus, high-performance display characteristics without unevenness in display can be obtained. In this case, if the same etching solution as that for the Al — Mo thin film is used in the wet etching, the pure Mo film is etched drastically, and therefore, it is necessary to prepare a new etching solution dedicated to pure Mo. However, as in the present embodiment, since the corrosion rate is reduced by adding 2.5 to 20 wt% of Nb to Mo and approaches the corrosion rate of the AlNd thin film, the MoNb thin film can be corroded at the same corrosion rate as the AlNd thin film, which has an advantage of avoiding the complexity of the process.
Further, since the high-reflectance metal 24 of the third metal thin film is made of AlNd alloy in which 0.5 to 3 wt% of Nd is added to Al, it is possible to minimize the decrease in reflectance after the formation of the uppermost Cr25 layer and the removal of corrosion, compared to the conventional Al alloy, and to obtain a transmissive liquid crystal display device having bright display characteristics. That is, as shown in fig. 10, in the case of using the conventional Al-0.2 wt% Cu alloy, the reflectance R is reduced by 10% or more depending on the wavelength λ compared to the case of using the Al-1.0 wt% Nd alloy in which Nd is added to Al, as shown in fig. 11 of the present embodiment, and it is found that the reflectance R is not substantially reduced after the formation and removal of Cr, compared to the case of using the conventional Al-0.2 wt% Cu alloy in which the Cr layer is formed and then the blanket etching is removed. Here, although a Cr film is used as the uppermost layer, any alloy may be used instead of the Cr film as long as it can suppress a cell reaction with ITO in a resist developer and selectively corrode an Al — Nd film, and for example, Ta, W, Ti, or the like can be used.
In addition to embodiment 6, the transmissive liquid crystal display device according to the embodiment of the present invention can have the same effects as those shown in table 1 by changing the configurations of the first and second metal thin films according to the purpose, as in embodiments 2 to 5 of the reflective liquid crystal display device.
In embodiments 1 to 6, as the reflective pixel electrode forming step, as shown in fig. 8 or fig. 19, a three-layer Cr/AlNd/Cr film is formed, reflective pixel patterns 23 and 24 are formed by etching, and then the uppermost Cr film 25 is entirely etched away by etching to expose the surface of the AlNd film in the intermediate layer, thereby forming reflective pixel electrodes 23 and 24, but a MoNb alloy in which 2.5 to 20 wt% of Nb is added to Mo may be used as the lowermost layer 23, and an Al/MoNb two-layer Al alloy film of an Al alloy film may be formed as the reflective film 24 on the uppermost layer. In this case, the lowermost MoNb film 23 is a barrier layer formed to prevent a step disconnection defect of the Al film 24 in the bottom surface of the pixel drain contact hole 17 and to prevent the Al film 24 from being directly formed on the ITO films of the gate terminal pad 21 and the source terminal pad 22, similarly to the Cr films 23 of embodiments 1 to 6. If AlNd24 is directly formed on the ITO surface without forming the lowermost Cr23 layer, an AlOx reaction layer is generated at the ITO/AlNd interface, and therefore, even after the third metal thin film is removed by etching, damage remains on the surfaces of the terminal pads ITO21 and 22, and the terminal resistance increases, which causes display defects.
In embodiments 1 to 6, the uppermost Cr layer of the third metal thin film Cr/AlNd/Cr trilayer film is a barrier layer for preventing corrosion of the terminal pads 21, 22 due to a battery reaction between Al and the underlying ITO in a developer during resist patterning in a photolithography step, but when MoNb is used as the lowermost layer, corrosion of the terminal pads 21, 22 due to a battery reaction between Al and the underlying ITO in a resist developer in a photolithography step can be prevented without formingthe Cr film 25 on the upper layer of the Al film. Therefore, the entire surface etching removal step of the uppermost Cr film 25 in fig. 9 or 20 after patterning the reflective electrode can be omitted, and the Al/MoNb double-layer film can be etched at once using a known chemical solution containing phosphoric acid + nitric acid + acetic acid, so that the reflective pixel electrode forming step can be greatly simplified.
In the preferred embodiment, in the step of fig. 8 or fig. 19, a MoNb alloy film 23 in which 2.5 to 20 wt% of Nb is added to Mo at 100nm is formed as the third metal thin film of the reflective electrode by a known sputtering method using Ar gas, and then an AlNd alloy 24 in which 0.5 to 3 wt% of Nd is added to Al at 300nm in thickness is formed to form an AlNd/MoNb double layer film. Then, the reflective pixel electrodes 23 and 24 are collectively etched using a known chemical solution containing phosphoric acid + nitric acid + acetic acid as an Al etchant. The known solution containing phosphoric acid + nitric acid + acetic acid can be the same as the AlNd — N/AlNd bilayer film of embodiment 1. Then, the resist pattern is removed, thereby completing the reflective liquid crystal display devices of embodiments 1 to 5 and the transmissive liquid crystal display device of embodiment 6.
Since the step of forming and removing Cr on the upper layer of the Al film 24 is omitted, it is not necessary to consider deterioration of the reflection characteristics of the Al film, and the Al film 24 may be made of, for example, an AlNd alloy, pure Al, or an AlCu alloy in which 0.1 to 1 wt% of Cu is added to Al.
Fig. 21 to 23 show the change characteristics of the reflectance R when an alignment control film for liquid crystal alignment is formed on a film of pure Al, Al-0.2 wt% Cu, or Al-1 wt% Nd as an example of the reflective pixel electrode material. Here, table 2 shows the reflectance (with respectto a white floor) of each material film when the measurement wavelength was changed. The measurement apparatus used was a spectrophotometer U-3000 (trade name) manufactured by Hitachi, Ltd.
TABLE 2 reflectance characteristics of the materials
Measuring wavelength (nm) Pure Al Pure Al + is taken Oriented film Al-0.2 weight The content of -0.2% by weight Cu + Alignment film Al-1.0 weight Amount% Nd Al-1.0 weight % Nd + oriented film
800 85.4 77.4 85.4 77.4 86.7 75.7
775 86.2 78.6 86.6 79.5 87.5 76.2
750 87.7 79.9 88.8 82.3 89 77.3
725 87.7 80.4 88.7 83.1 88.8 77.6
700 88.5 81.3 89.2 84.2 89.5 78.7
675 89 81.7 89.8 84.4 89.8 80.3
650 89.6 82.1 90.4 84.2 90.4 82.2
625 90 82.3 91 83.6 90.8 84.7
600 90.1 81.9 91.6 82.6 91.6 86.8
575 90.3 81.8 91.7 82.7 91.3 87.8
550 91 81.3 92.1 83.2 92.1 88.8
525 91.6 81.1 92.7 84.7 92.9 88.2
500 91.4 79.9 92.8 85.2 92.7 86.6
475 92 79.8 93.4 86.2 93.5 86.7
450 92.5 77.6 93.9 84.9 94 87.1
425 92.5 75.9 94.2 83.5 94.4 86.7
400 92.2 74 94.4 82.5 94.5 86.9
375 92 72.3 94.5 82 94.7 87.1
350 92.1 71.1 95.9 79.3 96 88.6
325 91.4 68.6 95.3 75.4 96.1 86.7
300 89.1 59.4 94.8 60.5 96 67.8
275 88.9 23.2 96 18.5 98.7 30.4
250 88 11.3 96 10.5 100 9.1
225 79 10.8 83.3 10.1 90 10.2
200 71.6 11.4 71.3 11.7 69.6 11.8
The alignment control film was formed by coating a polyimide film with a film thickness of 100nm by spin coating and drying the film. The reflectance R decreased as a whole if the orientation control film was formed on the Al film, but in the case of the Al-0.2 wt% Cu alloy film (see fig. 22) and the Al-1 wt% Nd alloy film (see fig. 23), the reflectance R decreased less than that of the pure Al film (see fig. 21), and a good reflectance could be maintained. Particularly in the case of a pure Al film, the reflectance R on the short wavelength side where the wavelength λ is 450nm or less has a large rate of decrease, so that there is a possibility that the chromaticity as a whole may be changed to yellowish or reddish. Therefore, it is more preferable to use an AlNd alloy film in which 0.5 to 3 wt% of Nd is added to Al or an AlCu alloy film in which 0.1 to 1 wt% of Cu is added to Al as the Al film 24.
In the reflective liquid crystal display device and the transflective liquid crystal display device thus completed, although the reflective electrode has a double-layer structure of AlNd/MoNb, corrosion of the terminal pad ITO films 21 and 22 due to a cell reaction in a resist developer is not observed at all. Further, the present inventors have conducted various studies and found that the Al — ITO cell reaction suppressing effect in the AlNd/MoNb double-layer structure can be explained as follows.
That is, it is known that the MoNb alloy is a metal which is easily hydrogen-foamed (has a low hydrogen foaming potential), and a part of the MoNb alloy causes a hydrogen foaming reaction by contacting a developing solution through a substrate peripheral portion, a pinhole, or the like The effect of making the oxidation-reduction potential of the entire substrate noble is strong, and the effect of reducing or preventing the reduction corrosion of ITO is large. The oxidation-reduction potentials of AlNd, Cr, and Mo-5% Nb in a common developer (2.38 wt% aqueous TMAH solution) are shown in Table 3.
TABLE 3 Oxidation-reduction potential in developing solution
Sample (I) Oxidation reduction potential (mV：vsAg/AgCl)
Al-1.0 wt.% Nd -1900
Cr -100
Mo-5 wt% Nd -580
Impregnating AlNd and Cr according to the area ratio of 1: 1 -1740
Impregnating AlNd and MoNb according to the area ratio of 1: 1 -1430
Substrate with 300nm AlNd continuously formed on 50nm MoNb film -300
The oxidation-reduction potential when each metal was immersed in the developer in a monomeric manner was Al: 1900mV (vsAg/AgCl: same below), Cr: -100mV, Mo: as compared with Mo, Cr is more noble in potential than Mo. Since ITO has a potential of about-1000 mV or less at which ITO starts to be corroded in a developer, ITO is immersed in Al after Al is formed on an ITO patternIn the developing solution, it is expected that the ITO will be corroded drastically when it comes into contact with the developing solution through a pinhole or the like. Next, the redox potentials when AlNd and Cr or MoNb were immersed in the developer simultaneously in an area of 1: 1 were compared. Compared with AlNd and Cr, the silver-based composite material is-1740 mV, and-1430 mV when AlNd and MoNb are immersed in a developing solution at the same time, which is more expensive than the case of AlNd and Cr. While foaming that did not occur in Cr was observed from the surface of MoNb, AlNd was completely dissolved in about 2 minutes. The reason why MoNb, which is a base material having a lower redox potential, makes the potential of AlNd noble is more powerful than Cr when used alone, is that it foams with hydrogen Consuming electrons in the substrate. The concept of this mechanism is shown in fig. 24 to 25. As shown in fig. 24, when the Cr film 27 is used as the lower layer of the Al layer 26, Al26 is dissolved ( ) The electrons 30 generated in (c) facilitate the reduction of the ITO28 (particularly inthe vicinity of the pinholes 31). On the other hand, as shown in fig. 25, in the case of using the Mo film 29 as the lower layer of the Al layer 26, Al26 is dissolved ( ) The electrons 30 produced in (c) reduce hydrogen ions 32 (b ) Therefore, it is difficult to cause reduction of ITO 28. Further, the oxidation-reduction potential of the laminated substrate on which AlNd was continuously formed on MoNb was measured when the substrate was immersed in a developer, and it was confirmed that-300 mV was obtained and the level of ITO corrosion was not reached, which was expensive. In comparison with the above results, the following facts can be explained: even if the Al alloy film having MoNb as the lower layer does not have an upper layer film for preventing the battery reaction, ITO reduction corrosion due to the battery reaction of Al and ITO during development does not occur.
However, in embodiments 1 to 6, although the transparent conductive film of the pixel electrode 20 of the transflective pixel portion or the terminal pads 21 and 22 is etched in a solution containing hydrochloric acid + acetic acid using an ITO (indium oxide + tin oxide) film, if there is a defect or the like in the interlayer insulating films 6, 13, and 14, the chemical solution containing hydrochloric acid + acetic acid penetrates, and the first and second metal thin films of the lower layer made of AlNd alloy or MoNb alloy are etched, thereby causing a disconnection defect in the wiring or the electrode. In such a case, it is preferable to form the transparent conductive film in an amorphous state. Since the amorphous transparent conductive film is chemically unstable and can be etched with a weak acid such as oxalic acid, it is possible to prevent the disconnection corrosion of the lower AlNd film or MoNb film due to the penetration of the chemical solution. On the other hand, in the amorphous transparent conductive film, when the third metal thin film Cr/AlNd/Cr, AlCu/MoNb, or AlNd/MoNb laminated film is etched in the subsequent reflective pixel electrode forming step, the terminal pads 21 and 22 and the transmissive pixel electrode 20 formed of the amorphous transparent conductive film are etched. Therefore, the transparent conductive film after oxalic acid etching processing of the terminal pads 21 and 22 in an amorphous state and the pixel electrode 20 needs to be in a chemically stable crystalline state.
As a preferable example of such a transparent conductive film, a ternary transparent conductive film in which zinc oxide is added to ITO (indium oxide + tin oxide) or a conventionally known ITO target is used, and Ar gas and O are used2Gas is added with H2The mixed gas of O gas is used as a sputtering gas to form a film, so that an amorphous ITO film can be used. The amorphous transparent conductive film according to these embodiments can be brought into a chemically stable crystalline state by a heating treatment at about 170 to 230 ℃. Therefore, the transparent conductive films 20, 21, and 22 can be brought into a chemically stable crystalline state by performing an annealing treatment at about 200 ℃ after the step of fig. 7 or 18, or by performing a substrate heating step in the sputtering deposition of the third metal thin film of fig. 8 or 19.

Claims (10)

1. A method of manufacturing a reflective liquid crystal display device, comprising:
a first step of forming a first metal thin film on a transparent insulating substrate and forming a gate wiring and a gate electrode by using a first photolithography process;
a second step of forming a gate insulating film, a semiconductor activefilm, and an ohmic contact film in this order and forming a semiconductor layer by a second photolithography process;
a third step of forming a second metal thin film and forming a source wiring, a source electrode, a drain electrode, and a channel portion of the thin film transistor by using a third photolithography process;
a fourth step of forming an interlayer insulating film and forming a concave-convex shape on the surface of the pixel electrode portion and contact holes reaching the gate wiring terminal portion, the source wiring terminal portion, and the drain electrode by using a fourth photolithography process; and
a fifth step of forming a third metal thin film and forming a pixel electrode by using a fifth photolithography process,
the first metal thin film is a double-layer film including an AlNd film and an AlNd film formed on the AlNd film and to which at least one element selected from nitrogen, carbon, and oxygen is added.
2. The method of manufacturing a reflective liquid crystal display device according to claim 1, wherein the first metal thin film is an alloy in which Nb is added to Mo.
3. The method of manufacturing a reflective liquid crystal display device according to claim 1, wherein the second metal thin film is a three-layer film of MoNb or MoNb/AlNd/MoNb.
4. The method of manufacturing a reflective liquid crystal display device according to claim 1, wherein the third metal thin film is formed by forming a three-layer film of Cr/AlNd/Cr, patterning the three-layer film, and removing an upper Cr layer.
5. The method of manufacturing a reflective liquid crystal display device according to claim 1, wherein the third metal thin film is a double-layer film of AlCu/MoNb or AlNd/MoNb.
6. A method for manufacturing a transflective liquid crystal display device, the method comprising:
a first step of forming a first metal thin film on a transparent insulating substrate, and forming a gate wiring and a gate electrode by using a first photolithography process;
a second step of forming a gate insulating film, a semiconductor active film, and an ohmic contact film in this order and forming a semiconductor layer by a second photolithography process;
a third step of forming a second metal thin film and forming a source wiring, a source electrode, a drain electrode, and a channel portion of the thin film transistor by using a third photolithography process;
a fourth step of forming an interlayer insulating film and forming a concave-convex shape on the surface of the pixel electrode portion, an opening portion of the pixel transmission electrode portion, and contact holes reaching the gate wiring terminal portion, the source wiring terminal portion, and the drain electrode by using a fourth photolithography process;
a fifth step of forming a transparent conductive film and forming a transmissive pixel electrode and a terminal pad by using a fifth photolithography process; and
a sixth step of forming a third metal thin film and forming a reflective pixel electrode by a sixth photolithography process,
the first metal thin film is a double-layer film including an AlNd film and an AlNd film formed on the AlNd film and to which at least one element selected from nitrogen, carbon, and oxygen is added.
7. The method of manufacturing a transflective liquid crystal display device according to claim 6, wherein the first metal thin film is an alloy in which Mo is added with Nb.
8. The method of manufacturing a transflective liquid crystal display device according to claim 6, wherein the second metal thin film is a MoNb or a MoNb/AlNd/MoNb three-layer film.
9. The method of manufacturing a transflective liquid crystal display device according to claim 6, wherein the third metal thin film is formed by forming a three-layer film of Cr/AlNd/Cr, patterning the three-layer film, and removing the upper Cr layer.
10. The method of manufacturing a transflective liquid crystal display device according to claim 6, wherein the third metal thin film is a bilayer film of AlCu/MoNb or AlNd/MoNb.
CNB2004100841709A 2003-10-16 2004-10-15 Reflective and semi-transmission type liquid crystal display device and producing method thereof Expired - Fee Related CN100421014C (en)

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