Patent Abstract:
A liquid crystal display using horizontal electric field and a method of fabricating the liquid crystal display device that are capable of reducing the number of mask processes are provided.  
     The liquid crystal display of horizontal electric field applying type according to the present invention includes: a thin film transistor array substrate, wherein the thin film transistor array substrate includes an effective display area having a gate line, a common line parallel to the gate line, a data line intersected and isolated with the gate line and the common line with a gate insulating film therebetween to define a pixel area, a thin film transistor formed on each intersection of the gate line and the data line, a passivasion film for protecting the thin film transistor, a common electrode formed in the pixel area and connected to the common line and a pixel electrode connected to the thin film transistor and formed to produce horizontal electric field along with the common electrode in the pixel area, and a pad area having a gate pad formed with at least one conductive layer included in the gate line, a data pad formed with at least one conductive layer included in the data line, a common pad formed with at least one conductive layer included in the common line, which are formed on a lower substrate to form the thin film transistor array substrate; a color filter array substrate combined with the thin film transistor array substrate as facing each other; a driving integrated circuit mounted on the substrate in order to directly connect to any one of the gate pad and the data pad; and a package mold the driving integrated circuit.

Full Description:
[0001]    This application claims the benefit of the Korea Patent Application No. P03-21117 filed on Apr. 3, 2003, which is hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a liquid crystal display using horizontal electric field, and more particularly to a liquid crystal display and a fabricating method thereof that are capable of reducing the number of mask processes.  
           [0004]    2. Description of the Related Art  
           [0005]    Generally, liquid crystal displays (LCDs) control light transmittance of liquid crystal material using an electric field to thereby display a picture. The liquid crystal displays are classified into a vertical electric field type and a horizontal electric field type in accordance with a direction of the electric field driving the liquid crystal.  
           [0006]    The liquid crystal display of vertical electric field type, in which a common electrode formed on an upper substrate and a pixel electrode formed on a lower substrate are arranged as facing each other, drives a liquid crystal of a twisted nematic mode (TN) by a vertical electric field formed between the common electrode and the pixel electrode. The liquid crystal display of vertical electric field type has an advantage of a large aperture ratio, while it has a defect of a narrow viewing angle about 90°.  
           [0007]    The liquid crystal display of horizontal electric field type drives a liquid crystal of in plane switch (hereinafter referred to as “IPS”) mode by a horizontal electric field between the pixel electrode and the common electrode disposed in parallel on the lower substrate. The liquid crystal display of horizontal electric field type has an advantage of an wide viewing angle about 160°. Hereinafter, the liquid crystal display of horizontal electric field type will be described in detail.  
           [0008]    The liquid crystal display of the horizontal electric field type comprises a thin film transistor array substrate (a lower substrate) and a color filter array substrate (an upper substrate) as faced and joined each other, a spacer for uniformly maintaining a cell gap between two substrates and a liquid crystal injected into a space provided by the spacer.  
           [0009]    The thin film transistor array substrate includes a plurality of signal lines for forming a horizontal electric field on a basis of a pixel, a plurality of thin film transistors, and an alignment film applied for a liquid crystal alignment thereon. The color filter array substrate includes a color filter for representing a color, a black matrix for preventing a light leakage and an alignment film applied for a liquid crystal alignment thereon.  
           [0010]    In such a liquid crystal display, since the thin film transistor array substrate involves a semiconductor process and requires a plurality of mask processes, the manufacturing process is complicate to be a major rise factor in the manufacturing cost of the liquid crystal display panel. In order to solve this, the thin film transistor array substrate has been developed toward a reduction in the number of mask processes. This is because one mask process includes a lot of processes such as thin film deposition, cleaning, photolithography, etching, photo-resist stripping and inspection processes, etc. Recently, there has been highlighted a four-round mask process in which one mask process is reduced from the existent five-round mask process that is employed as a standard mask process.  
           [0011]    [0011]FIG. 1 is a plan view illustrating a related art thin film transistor substrate of horizontal electric type using the four-round mask process, and FIG. 2 is a sectional view of the thin film transistor array substrate taken along the I-I′ and II-II′ line in FIG. 1.  
           [0012]    Referring to FIGS. 1 and 2, the related art thin film transistor array substrate of horizontal electric type comprises a gate line  2  and a data line  4  formed on a lower substrate  45  in such a manner to intersect each other, a thin film transistor  6  formed at each intersection, a pixel electrode  14  and a common electrode  18  formed in order to apply the horizontal electric field in a pixel regions defined by the intersection and a common line  16  connected to the common electrode  18 . Moreover, the related art thin film transistor array substrate further comprises a storage capacitor  20  formed at an overlapped portion between the pixel electrode  14  and the common line  16 , a gate pad  24  connected to the gate line  2 , and a data pad  30  connected to the data line  4  and a common pad  36  connected to the common line  16 .  
           [0013]    The gate line  2  supplies a gate signal to the gate electrode  8  of the thin film transistor  6 . The data line  4  supplies a pixel signal to the pixel electrode  14  via a drain electrode  12  of the thin film transistor  6 . The gate line  2  and the data line  4  are formed in an intersection structure to thereby define the pixel region  5 .  
           [0014]    The common line  16  is formed in parallel with the gate line  2  with the pixel region  5  positioned between the common line  16  and the gate line  2  to supply a reference voltage for driving the liquid crystal to the common electrode  18 .  
           [0015]    The thin film transistor  6  responds to the gate signal of the gate line  2  so that the pixel signal of the data line  4  is charged to the pixel electrode  14 . To this end, the thin film transistor  6  comprises a gate electrode  8  connected to the gate line  2 , a source electrode  10  connected to the data line  4  and a drain electrode  12  connected to the pixel electrode  14 . Further, the thin film transistor  6  includes an active layer  48  overlapping with the gate electrode  8  with a gate insulating film  46  positioned between the thin film transistor  6  and the gate electrode  8  and defining a channel between the source electrode  10  and the drain electrode  12 . The active layer  48  is formed to overlap with the data line  4 , a data pad lower electrode  32  and a storage electrode  22 . On the active layer  48 , an ohmic contact layer  50  for making an ohmic contact with the data line  4 , the source electrode  10 , the drain electrode  12 , the data pad lower electrode  32  and the storage electrode  22  is further formed.  
           [0016]    The pixel electrode  14 , which is connected to the drain electrode  12  of the thin film transistor  6  via a first contact hole  13  passing through a passivation film  52 , is formed in the pixel region  5 . Particularly, the pixel electrode  14  comprises a first horizontal part  14 A connected to the drain electrode  12  and formed in parallel with adjacent gate line  2  and a second horizontal part  14 B formed to overlap with the common line  16  and a finger part  14 C formed in parallel with the common electrode  18 .  
           [0017]    The common electrode  18  is connected to the common line  16  and is formed in the pixel region  5 . In addition, the common electrode  18  is formed in parallel with the finger part  14 C of the pixel electrode  14  in the pixel region  5 .  
           [0018]    Accordingly, a horizontal electric field is formed between the pixel electrode  14  to which the pixel signal is supplied via the thin film transistor  6  and the common electrode  18  to which the reference voltage is supplied via the common line  16 . Moreover, the horizontal electric field is formed between the finger part  14 C of the pixel electrode  14  and the common electrode  18 . The liquid crystal molecules arranged in the horizontal direction between the thin film transistor array substrate and the color filter array substrate by the horizontal electric field becomes to rotate due to a dielectric anisotropy. The light transmittance transmitting the pixel region  5  differs in accordance with a rotation amount of the liquid crystal molecules and thereby the pictures can be represented.  
           [0019]    The storage capacitor  20  consists of the common line  16 , a storage electrode  22  overlapping with the common line  16  with the gate insulating film  46 , the active layer  48  and the ohmic contact layer  50  positioned therebetween, and a pixel electrode  14  connected via a second contact hole  21  passing through the storage electrode  22  and the passivation film  52 . The storage capacitor  20  allows a pixel signal charged in the pixel electrode  14  to be maintained stably until the next pixel signal is charged.  
           [0020]    The gate line  2  is connected, via the gate pad  24 , to a gate driver (not shown). The gate pad  24  consists of a gate pad lower electrode  26  extended from the gate line  2 , and a gate pad upper electrode  28  connected, via a third contact hole  27  passing through the gate insulating film  46  and the passivation film  52 , to the gate pad lower electrode  26 .  
           [0021]    The data line  4  is connected, via the data pad  30 , to the data driver (not shown). The data pad  30  consists of a data pad lower electrode  32  extended from the data line  4 , and a data pad upper electrode  34  connected, via a fourth contact hole  33  passing through the passivation film  52 , to the data pad lower electrode  32 .  
           [0022]    The common line  16  supplied with the reference voltage from the reference voltage source of exterior (not shown) via the common pad  36 . The common pad  36  consists of a common pad lower electrode  38  extended from the common line  16 , and a common pad upper electrode  40  connected, via a fifth contact hole  39  passing through the gate insulating film  46  and the passivation film  52 , to the common pad lower electrode  38 .  
           [0023]    A method of fabricating the thin film transistor substrate having the above-mentioned structure using the four-round mask process will be described in detail with reference to FIGS. 3A to  3 D.  
           [0024]    Referring to FIG. 3A, a first conductive pattern group including the gate line  2 , the gate electrode  8  and the gate pad lower electrode  26  is formed on the lower substrate  45  using the first mask process.  
           [0025]    More specifically, a first metal layer  42  and a second metal layer  44  are sequentially formed on the upper substrate  45  by a deposition technique such as a sputtering to form a gate metal layer of double-structure. Then, the gate metal layer is patterned by the photolithography and the etching process using a first mask to thereby form the first conductive pattern group including the gate line  2 , the gate electrode  8 , the gate pad lower electrode  26 , the common line  16 , common electrode  18  and the common pad lower electrode  38 . Herein, the first metal layer  42  is formed with an aluminum system metal and the second metal layer  44  is formed with a chrome (Cr) or a molybdenum (Mo).  
           [0026]    Referring to FIG. 3B, the gate insulating film  46  is formed on the lower substrate  45  provided with the first conductive pattern group. Further, a semiconductor pattern group including the active layer  48  and the ohmic contact layer  50  and a second conductive pattern group including the data line  4 , the source electrode  10 , the drain electrode  12 , the data pad lower electrode  32  and the storage electrode  22  are formed on the gate insulating film  46  using the second mask process.  
           [0027]    More specifically, the gate insulating film  46 , a first semiconductor layer, a second semiconductor layer and a data metal layer are sequentially formed on the lower substrate  45  provided with the first conductive pattern group by deposition techniques such as the plasma enhanced chemical vapor deposition (PECVD) and the sputtering, etc. Herein, the gate insulating film  46  is made of an inorganic insulating material such as silicon oxide (SiO x ) or silicon nitride (SiN x ). The first semiconductor layer is made of amorphous silicon that an impurity is not doped and the second conductor layer is made of amorphous silicon that an impurity of a N type or P type is doped. The data metal layer is made of a molybdenum (Mo), a titanium (Ti), tantalum (Ta) or a molybdenum alloy, etc.  
           [0028]    Then, a photo-resist pattern is formed on the data metal layer by the photolithography using a second mask. In this case, a diffractive exposure mask having a diffractive exposing part at a channel portion of the thin film transistor is used as a second mask, thereby allowing a photo-resist pattern of the channel portion to have a lower height than other photo-resist patterns of region portions.  
           [0029]    Subsequently, the data metal layer is patterned by a wet etching process using the other photo-resist patterns to thereby provide the data pattern including the data line  4 , the source electrode  10 , the drain electrode  12  being integral to the source electrode  10  and the storage electrode  22 .  
           [0030]    Next, the first semiconductor layer and the second semiconductor layer are patterned at the same time by a dry etching process using the same photo-resist pattern to thereby provide the ohmic contact layer  50  and the active layer  48 .  
           [0031]    The photo-resist pattern having a relatively low height is removed from the channel portion by the ashing process and thereafter the source electrode, the drain electrode and the ohmic contact layer  50  of the channel portion are etched by the dry etching process. Thus, the active layer  48  of the channel portion is exposed to separate the source electrode  10  from the drain electrode  12 .  
           [0032]    Thereafter, a remainder of the photo-resist pattern on the second conductive pattern group is removed using the stripping process.  
           [0033]    Referring to FIG. 3C, the passivation film  52  including first to fifth contact holes  13 ,  21 ,  27 ,  33  and  39  are formed on the gate insulating film  46  provided with the second conductive pattern group using the third mask process.  
           [0034]    More specifically, the passivation film  52  is entirely formed on the gate insulating film  46  provided with the data pattern by a deposition technique such as the plasma enhanced chemical vapor deposition (PECVD). The passivation film  52  is patterned by the photolithography and the etching process using the third mask to thereby form first to fifth contact holes  13 ,  21 ,  27 ,  33  and  39 . The first contact hole  13  is formed in such a manner to pass through the passivation film  52  and exposes the drain electrode  12 , whereas the second contact hole  21  is formed in such a manner to pass through the passivation film  52  and exposes the storage electrode  22 . The third contact hole  27  is formed in such a manner to pass through the passivation film  52  and the gate insulating film  46  and exposes the gate pad lower electrode  26 , whereas the fourth contact hole  33  is formed in such a manner to pass through the passsivation film  52  and exposes the data pad lower electrode  32 , and the fifth contact hole  39  is formed in such a manner to pass through the passivation film  52  and the gate insulating film  46  and exposes the common pad lower electrode  38 . Herein, when a metal which has high ratio of dry etching like a molybdenum (Mo) is used for the data metal, the first contact hole  13 , the second contact hole  21  and the forth contact hole  33  are formed in such a manner to pass through to the drain electrode  12 , the storage electrode  22  and the data pad lower electrode  32 , respectively, to thereby expose their side.  
           [0035]    The passivaion film  52  is made of an inorganic insulating material such as the gate insulating film  46  or an organic insulating material having a small dielectric constant such as an acrylic organic compound, BCB (benzocyclobutene) or PFCB (perfluorocyclobutane), etc.  
           [0036]    Referring to FIG. 3D, a third conductive pattern group including the pixel electrode  14 , the gate pad upper electrode  28 , the data pad upper electrode  34  and the common pad upper electrode  40  is formed on the passivation film  52  using the fourth mask process.  
           [0037]    More specifically, a transparent conductive film is coated onto the passivation film  52  by a deposition technique such as the sputtering, etc. Then, the transparent conductive film is patterned by the photolithography and the etching process using a fourth mask, to thereby provide the third conductive pattern group including the pixel electrode  14 , the gate pad upper electrode  28 , the data pad upper electrode  34  and the common pad upper electrode  40 . The pixel electrode  14  is electrically connected, via the first contact hole  13 , to the drain electrode  12  while being electrically connected, via the second contact hole  21 , to the storage electrode  22 . The gate pad upper electrode  28  is electrically connected, via the third contact hole  37 , to the gate pad lower electrode  26 . The data pad upper electrode  34  is electrically connected, via the fourth contact hole  33 , to the data pad lower electrode  32 . The common pad upper electrode  40  is electrically connected, via the fifth contact hole  39 , to the common pad lower electrode  38 .  
           [0038]    In this connection, the transparent conductive film may be made of an indium-tin-oxide (ITO), a tin-oxide (TO), an indium-zinc-oxide (IZO) or an indium tin zinc oxide (ITZO).  
           [0039]    As described above, the related art thin film transistor array substrate of horizontal electric field type and the manufacturing method thereof adopts a four-round mask process, thereby reducing the number of manufacturing processes in comparison to the five-round mask process and hence reducing a manufacturing cost to that extent. However, since the four-round mask process also still has a complex manufacturing process and a limit in reducing a cost, there has been required an approach that is capable of more simplifying the manufacturing process and more reducing the manufacturing cost.  
         SUMMARY OF THE INVENTION  
         [0040]    Accordingly, it is an object of the present invention to provide a liquid crystal display using horizontal electric field and a method of fabricating a liquid crystal display device that are capable of reducing the number of mask processes.  
           [0041]    In order to achieve these and other objects of the invention, the liquid crystal display of horizontal electric field applying type according to the present invention comprises: a thin film transistor array substrate, wherein the thin film transistor array substrate includes an effective display area having a gate line, a common line parallel to the gate line, a data line intersected and isolated with the gate line and the common line with a gate insulating film therebetween to define a pixel area, a thin film transistor formed on each intersection of the gate line and the data line, a passivasion film for protecting the thin film transistor, a common electrode formed in the pixel area and connected to the common line and a pixel electrode connected to the thin film transistor and formed to produce horizontal electric field along with the common electrode in the pixel area, and a pad area having a gate pad formed with at least one conductive layer included in the gate line, a data pad formed with at least one conductive layer included in the data line, a common pad formed with at least one conductive layer included in the common line, which are formed on a lower substrate to form the thin film transistor array substrate; a color filter array substrate combined with the thin film transistor array substrate as facing each other; a driving integrated circuit mounted on the substrate in order to directly connect to any one of the gate pad and the data pad; and a package mold material for capsulating the pads and the driving integrated circuit.  
           [0042]    The passivation film is formed on the effective display area except for the pad region.  
           [0043]    The gate insulating film is formed on the gate pad, a lower portion of the data pad, the common pad and the effective display area.  
           [0044]    The driving integrated circuit includes a gate driving integrated circuit connected to the gate pad.  
           [0045]    The driving integrated circuit further includes a data driving integrated circuit connected to the data pad.  
           [0046]    The liquid crystal display of horizontal electric field applying type further comprises a plurality of signal supplying lines for supplying a driving signal to the driving integrated circuit.  
           [0047]    The liquid crystal display of horizontal electric field applying type further comprises a connector to which a conductive film for supplying a driving signal to the signal supplying line is attached.  
           [0048]    The liquid crystal display of horizontal electric field applying type further comprises a second package mold material for capsulating a boundary portion of the connector and the conductive film and a boundary portion of the lower substrate and the conductive film.  
           [0049]    Each of the gate line and the common line includes a main conductive layer and a subsidiary conductive layer for providing against an opening of the main conductive layer.  
           [0050]    Each of the gate pad and the common pad includes the main conductive layer and the subsidiary conductive layer, and wherein the subsidiary conductive layer has an exposed structure.  
           [0051]    Each of the gate pad and the common pad includes the subsidiary conductive layer.  
           [0052]    The main conductive layer includes at least one of an aluminum system metal, a copper, a molybdenum, a chrome and a tungsten which are a low resistance metal; and wherein the subsidiary conductive layer includes a titanium.  
           [0053]    The data line includes a main conductive layer and a subsidiary conductive layer for providing against the opening of the main conductive layer.  
           [0054]    The data pad includes the main conductive layer and the subsidiary conductive layer, and wherein the subsidiary conductive layer has an exposed structure.  
           [0055]    The data pad includes the subsidiary conductive layer.  
           [0056]    The main conductive layer includes at least one of an aluminum system metal, a copper, a molybdenum, a chrome and a tungsten which are a low resistance metal; and wherein the subsidiary conductive layer includes a titanium.  
           [0057]    The thin film transistor comprises: a gate electrode connected to the gate line; a source electrode connected to the data line; a drain electrode facing with the source electrode; and a semiconductor layer overlapped with the gate electrode with the gate insulating film therebetween to form a channel portion between the source electrode and the drain electrode.  
           [0058]    The drain electrode and the pixel electrode are made of an identical conductive layer.  
           [0059]    The semiconductor layer is formed on the gate insulating film along the data line, the source electrode, the drain electrode and the pixel electrode.  
           [0060]    In order to achieve these and other objects of the invention, a method for fabricating a liquid crystal display of horizontal electric field applying type includes: preparing a thin film transistor array substrate having an effective display area and a pad area formed on a lower substrate, wherein the effective display area includes a gate line, a common line parallel to the gate line, a data line intersected with the gate line and the common line with a gate insulating film therebetween to define a pixel area, a thin film transistor formed on each intersection of the gate line and the data line, a passivasion for protecting the thin film transistor, a common electrode formed in the pixel area and connected to the common line and a pixel electrode connected to the thin film transistor and formed to produce horizontal electric field along with the common electrode in the pixel area, and the pad area includes a gate pad formed with at least one conductive layer included in the gate line, a data pad formed with at least one conductive layer included in the data line, a common pad formed with at least one conductive layer included in the common line; preparing a color filter array substrate combined with the thin film transistor array substrate as facing each other; combining the thin film transistor array substrate and the color filter array substrate to expose the pad region; exposing the common pad, the gate pad and the data pad; mounting a driving integrated circuit on the substrate in order to directly connect to any one of the gate pad and the data pad; and capsulating a pad connected with the driving integrated circuit with a package mold material.  
           [0061]    The step of mounting the driving integrated circuit includes connecting the gate pad and the gate driving integrated circuit.  
           [0062]    The step of mounting the driving integrated circuit further includes connecting the data pad and data driving integrated circuit.  
           [0063]    The method according to claim  20 , further comprising the step of forming a plurality of signal supplying lines for supplying a driving signal to the driving integrated circuit.  
           [0064]    The method for fabricating a liquid crystal display of horizontal electric field applying type further comprises the step of attaching a connector connected to the signal supplying lines with a conductive film for supplying a driving signal to the signal supplying lines.  
           [0065]    The method for fabricating a liquid crystal display of horizontal electric field applying type further comprises the step of capsulating a boundary portion of the connector and the conductive film and a boundary portion of the lower substrate and the conductive film a second package mold material.  
           [0066]    The step of preparing a thin film transistor array substrate includes: forming, on the lower substrate, a first conductive pattern group including the gate line, a gate electrode connected to the gate line, the common line parallel to the gate line, the common electrode, the gate pad and the common pad; forming a gate insulating film on the substrate having the first conductive pattern group thereon; forming a semiconductor layer at a predetermined area on the gate insulating film and a second conductive pattern group having the date line, a source electrode of the thin film transistor connected with the data line, a drain electrode of the thin film transistor being opposite to the source electrode, a pixel electrode connected with the drain electrode and paralleled to the common electrode and the data pad; and forming a passivation film for covering the second conductive pattern group.  
           [0067]    The step of exposing the gate pad and the data pad includes etching the gate insulating film and the passivaion film using the color filter array substrate as the mask.  
           [0068]    At least one of the first and the second conductive pattern group is formed to have a double-layer structure having a main conductive layer and a subsidiary conductive layer for providing against the opening of the main conductive layer.  
           [0069]    The step of exposing the gate pad and the data pad includes exposing the subsidiary conductive layers of the gate pad and the common pad and the subsidiary conductive layer of the data pad.  
           [0070]    The main conductive layer includes at least one of an aluminum system metal, a copper, a molybdenum, a chrome and a tungsten which are a low resistance metal, and wherein the subsidiary conductive layer includes a titanium. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0071]    These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which:  
         [0072]    [0072]FIG. 1 is a plan view showing the related art thin film transistor array substrate of liquid crystal display of horizontal electric applying type;  
         [0073]    [0073]FIG. 2 is a sectional view of the thin film transistor array substrate taken along the lines I-I′ and II-II′ in FIG. 1;  
         [0074]    [0074]FIGS. 3A to  3 D are sectional sequentially views illustrating a method of manufacturing the thin film transistor array substrate shown in FIG. 2;  
         [0075]    [0075]FIG. 4 is a plan view showing a liquid crystal display of horizontal electric field applying type according to an embodiment of the present invention;  
         [0076]    [0076]FIG. 5 is a plan view showing the liquid crystal display panel shown in FIG. 4;  
         [0077]    [0077]FIG. 6 is a sectional view of the liquid crystal display panel taken along the lines III′-III′ and IV-IV′ in FIG. 4;  
         [0078]    [0078]FIG. 7A and FIG. 7B are a plan view and a sectional view for explaining a first mask process among a manufacturing method of a thin film transistor array substrate according to the embodiment of the present invention, respectively;  
         [0079]    [0079]FIGS. 8A to  8 C are sectional views for concretely explaining the first mask process among the manufacturing method of the thin film transistor array substrate according to the embodiment of the present invention;  
         [0080]    [0080]FIGS. 9A and 9B are a plan view and a sectional view for explaining a second mask process among the manufacturing method of a thin film transistor array substrate according to the embodiment of the present invention, respectively;  
         [0081]    [0081]FIGS. 10A to  10 F are sectional views for concretely explaining the second mask process among the manufacturing method of the thin film transistor array substrate according to the embodiment of the present invention;  
         [0082]    [0082]FIGS. 11A and 11B are a plan view and a sectional view for explaining a pad opening process according to the embodiment of the present invention, respectively;  
         [0083]    [0083]FIGS. 12A to  12 B are sectional views for concretely explaining the pad opening process according to the embodiment of the present invention;  
         [0084]    [0084]FIG. 13 is a sectional view showing pads of a first structure in the thin film transistor substrate according to the embodiment of the present invention;  
         [0085]    [0085]FIG. 14 is a sectional view showing pads of a second structure in the thin film transistor substrate according to the embodiment of the present invention;  
         [0086]    [0086]FIGS. 15A and 15B are a plan view and a sectional view for representing the drive IC mounted to the pads shown in FIGS. 13 and 14, respectively;  
         [0087]    [0087]FIGS. 16A and 16B are a plan view and a sectional view for representing a first package mold material formed at pad region on the thin film transistor array substrate;  
         [0088]    [0088]FIGS. 17A and 17B are a plan view and a sectional view for representing a flexible printed circuit supplying a driving signal to the drive IC formed at pad region of the thin film transistor array substrate according to the embodiment of the present invention in detail; and  
         [0089]    [0089]FIGS. 18A and 18B are a plan view and a sectional view for representing a second package mold material formed at pad region on the thin film transistor array substrate. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0090]    Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to FIGS.  4  to  18 B.  
         [0091]    [0091]FIG. 4 is a plan view representing a liquid crystal display of horizontal electric field applying type according to the present invention.  
         [0092]    Referring to FIG. 4, a liquid crystal display of horizontal electric field applying type according to the present invention comprises a gate drive integrated circuit (IC)  350  and a data drive IC  354  formed on a liquid crystal panel, and a flexible printed circuit (FPC)  354  supplying a driving signal to drive ICs  350  and  356 .  
         [0093]    The data drive ICs  356  are mounted by a chip on glass (COG) system on the lower substrate  145  and are connected to data lines  104  via the data pad. Therefore, the data drive ICs  356  supply data signals to the data lines  104 .  
         [0094]    For the sake of it, data control signals and data signals from a timing controller and a power source portion (not shown) on a PCB (Printed Circuit Board)  352  are supplied to a signal supplying line  208  via the FPC  354  and a COG connector  358 . A signal supplying line  208  is connected to an input terminal of each of the data drive ICs  356  through an input bump to thereby supply the data control signals and the data signals to the data drive IC  356 . The data drive IC  356  generates data driving signals using the data control signals and the data signals. The data driving signals are supplied to the data pad  130  through an output bump  286  connected to output terminals  284  of the data drive IC  356 .  
         [0095]    The gate drive ICs  350  are mounted by a COG system on the lower substrate  145  and are connected to gate lines  102  via the gate pad  124 . The gate drive ICs  350  supplies a gate signal to the gate line  102 .  
         [0096]    To this end, gate control signals and power source signals from a timing controller and a power source (not shown) on PCB (Printed Circuit Board)  352  are supplied to the signal supplying line  208  via the FPC  354  and the COG connector  358 . The signal supplying line  208  is connected to an input terminal of each of the gate drive ICs  350  through an input bump to thereby supply the gate control signals and the power source signals to the gate drive IC  350 . The gate drive IC  350  generates a gate-driving signal using the gate control signals and the power source signals. The gate driving signals are supplied to the gate pad  124  through an output bump  260  connected to output terminals  262  of the gate drive IC  350 .  
         [0097]    The FPC  354  supplies control signals and power source signals from a timing controller and a power source (not shown) on the PCB  352  to the gate drive IC  350  and the data drive IC  356  corresponding thereto. That is, an input pad of the FPC  354  is connected to the PCB  352  and an output pad of the FPC  354  is connected to the COG connector  358 . Further, any one of output pads  282  of the FPC  354  is connected to the common pad  130  using the ACF  182  including the conductive ball  184  as shown in FIGS. 5 and 6.  
         [0098]    On the hand, the signal supplying  208 , the pads, gate drive IC  350  and the data drive IC  356  connected on the lower substrate  145  are protected by a package mold material  252  as shown in FIG. 6. Further, the package mold material  252  is formed to capsulate a boundary portion of the FPC  354  and the COG connector  358  which are connected each other. The package mold material  252  is made of, for example, a sealing resin.  
         [0099]    As shown in FIGS. 5 and 6, a liquid crystal panel  360  is fabricated by combining, using a sealant  204 , a thin film transistor array substrate in which a thin film transistor array is formed on the lower substrate  145  and a color filter array substrate in which a color filter array  202  is formed on an upper substrate  200 .  
         [0100]    The thin film transistor array substrate comprises a gate line  102  and a data line  104 , which have a gate insulating film  146  therebetween, formed on a lower substrate  145  in such a manner to intersect each other, a thin film transistor  106  formed at each intersection of the gate line  102  and the data line  104 , a pixel electrode  114  and a common electrode  118  formed in order to apply the horizontal electric field in a pixel region defined by the interconnection and a common line  116  connected to the common electrode  118 . Moreover, the thin film transistor array substrate further comprises a storage capacitor  120  formed at an overlapped portion between a storage electrode  122  and the common line  116 , a gate pad  124  extended from the gate line  102 , and a data pad  130  extended form data line  104  and a common pad  136  extended from the common line  116 .  
         [0101]    The gate line  102  for supplying a gate signal and the data line  104  for supplying a data signal are formed in an intersection structure to thereby define a pixel region  105 .  
         [0102]    The common line  116  supplying a reference voltage used to drive the liquid crystal is formed in parallel with the gate line  102  with the pixel region  105  positioned between the common line  116  and the gate line  102 .  
         [0103]    The thin film transistor  106  responds to the gate signal of the gate line  102  so that the pixel signal of the data line  104  is charged and maintained in the pixel electrode  114 . To this end, the thin film transistor  106  comprises a gate electrode  108  connected to the gate line  102 , a source electrode included in the data line  104  and a drain electrode  112  connected to the pixel electrode  114 . In addition, the thin film transistor  106  further includes an active layer  148  overlapping with the gate electrode  108  with a gate insulating film  146  positioned therebetween and defining a channel between the source electrode and the drain electrode  112 .  
         [0104]    The active layer  148  is formed to overlap with the data line  104 , the data pad  130  and the storage electrode  122 . On the active layer  148 , an ohmic contact layer  150  for making an ohmic contact with the data line  104 , the drain electrode  112 , the data pad  130  and the storage electrode  122  is further provided.  
         [0105]    The pixel electrode  114  being integral to the drain electrode  112  of the thin film transistor  106  and the storage electrode  122  is formed in the pixel region  105 . Particularly, the pixel electrode  114  comprises a horizontal part  114 A extended in parallel with adjacent gate line  102  from the drain electrode  112  and a finger part  114 B extended from the horizontal part  114 A in vertical direction.  
         [0106]    The common electrode  118  is connected to the common line  116  and is formed in the pixel region  105 . Specially, the common electrode  118  is formed in parallel with the finger part  114 B of the pixel electrode  114  in the pixel region  105 .  
         [0107]    Accordingly, a horizontal electric field is formed between the pixel electrode  114  to which the pixel signal is supplied via the thin film transistor  106  and the common electrode  118  to which the reference voltage is supplied via the common line  116 . In practically, the horizontal electric field is formed between the finger part  14 B of the pixel electrode  114  and the common electrode  118 . The liquid crystal molecules arranged in the horizontal direction between the thin film transistor array substrate and the color filter array substrate by the horizontal electric field becomes to rotate due to a dielectric anisotropy. Further, the light transmittance transmitting the pixel region  105  differs in accordance with a rotation amount of the liquid crystal molecules and thereby the pictures can be represented.  
         [0108]    The storage capacitor  120  is comprised of the common line  116  and the storage electrode  122  overlapping with the common line  116 , wherein the storage electrode  122  has the gate insulating film  146 , the active layer  148  and the ohmic contact layer  150  between the storage capacitor  120  and the common line  116 , and being integral with the pixel electrode  114 . The storage capacitor  120  allows a pixel signal charged in the pixel electrode  114  to be maintained stably until the next pixel signal is charged.  
         [0109]    The gate line  102  is connected, via the gate pad  124 , to a gate driver IC  350  mounted on the lower substrate. The gate pad  124  is extended from the gate line  102  to thereby form structure in which a titanium Ti included to the gate line  102  is exposed. The gate drive IC  350  and the gate pad  124  are packaged for the protection thereof by the package mold material  252 .  
         [0110]    The common line  116  is connected to the FPC  354  for supplying the reference voltage from the power source of exterior (not shown) via the common pad  136 . The common pad  136  is extended from the common line  116  and has structure in which a titanium (Ti) included in the common line  116  is exposed.  
         [0111]    More specifically, the gate line  102 , the gate electrode  108 , the common line  116  and common electrode  118  have a double-layer structure of metal layers of a first and a second metal layers  142  and  144  as stacked. Any one of the metal layers is made of any metal that has a relatively high strength and corrosion resistance such as a titanium (Ti) and a tungsten (W). Whereas, another metal layer is made of a low resistance metal such as an aluminum (Al) system metal, a molybdenum (Mo) and a copper (Cu) that are conventionally employed as a gate metal.  
         [0112]    In this connection, in case where the first metal layer  142  is made of any metal that has a high strength and corrosion resistance, the gate pad  124  and the common pad  138  have structure in which the second metal layer  144  of an upper portion is removed and the first metal layer  142  of the lower portion is exposed. On the other hand, in case where the second metal layer  144  is made of any metal that has a high strength and corrosion resistance, the gate pad  124  and the common pad  138  have structure in which the second metal layer  144  of an upper portion is exposed.  
         [0113]    The data line  104  is connected to the data driver IC  356  via the data pad  130 . The data pad  130  is extended from the data line  104  to thereby get structure in which a titanium Ti and a tungsten (W) included to the data line are exposed. The data drive IC  356  and the data pad  130  are packaged for protection thereof by the package mold material  252 .  
         [0114]    In particular, the data line  104 , the drain electrode  112 , the pixel electrode  114  and the storage electrode  122  have a double-layer structure of metal layers stacked with a first and a second metal layers  154  and  156 . One metal layer of the metal layers is made of any metal that has a relatively high strength and corrosion resistance such as a titanium (Ti) and a tungsten (W). Whereas, another metal layer is made of a low resistance metal such as an aluminum (Al) system metal, a molybdenum (Mo) and a copper (Cu) that are generally employed as a gate metal.  
         [0115]    In this connection, in case where the first metal layer  154  is made of any metal having a high strength and corrosion resistance, the data pad  130  has structure in which the second metal layer  156  of an upper portion is removed and the first metal layer  154  of a lower portion is exposed. On the other hand, in case where the second metal layer  156  is made of any metal having a high strength and corrosion resistance, the data pad  130  has structure in which the second metal layer  156  of an upper portion is exposed.  
         [0116]    [0116]FIGS. 7A and 7B are a plan view and a sectional view for explaining a first mask process employed in a manufacturing method of the thin film transistor array substrate of horizontal electric applying type shown in FIGS. 4 and 5, respectively.  
         [0117]    As shown in FIGS. 7A and 7B, a first conductive pattern group including the gate line  102 , the gate electrode  108  and the gate pad  124 , the common line  116 , the common electrode  118  and the common pad  136  is formed on the lower substrate  145  using the first mask process.  
         [0118]    There will be explained the first mask process in detail with reference to FIGS. 8A to  8 C.  
         [0119]    As shown in FIG. 8A a first gate metal layer  142  and a second gate metal layer  144  are sequentially formed on the upper substrate  145  by a deposition method such as a sputtering, to thereby form a gate metal layer of double-layer structure. Herein, any one of the first gate metal layer  142  and the second gate metal layer  144  is made of any metal that has a relatively high strength and corrosion resistance such as a titanium (Ti) and a tungsten (W), whereas another metal layer is made of a metal such as an aluminum (Al) system metal, a molybdenum (Mo) and a copper (Cu). Subsequently, a photo-resist film is entirely formed on the second gate metal layer  144  and then a first mask  300  is arranged on the lower substrate  145  as shown in FIG. 8B. The first mask  300  comprises a mask substrate  304  which is a transparent material and a cut-off part formed on a cut-off region P 2  of the mask substrate  304 . Herein, region in which the mask substrate  304  is exposed becomes an exposure region P 1 . The photo-resist film is exposed using the first mask  300  as set forth above and developed, to thereby form the photo-resist pattern  306  in the cut-off region P 2  corresponding to the cut-off part  302  of the first mask  300 . The first and the second gate metal layer  142  and  144  are patterned by an etching process using the photo-resist pattern  306 , to thereby form the first conductive pattern group including the gate line, the gate electrode  108 , the gate pad  124 , the common line  116 , the common electrode  118  and the common pad  136  as shown in FIG. 8C.  
         [0120]    [0120]FIGS. 9A and 9B are a plan view and a sectional view for explaining a second mask process employed in the manufacturing method of the thin film transistor array substrate of horizontal electric applying type according to the embodiment of the present invention, respectively.  
         [0121]    At first, a gate insulating film  146  is formed on the lower substrate  145  provided with the first conductive pattern group by deposition method such as the plasma enhanced chemical vapor deposition (PECVD) or sputtering. The gate insulating film  146  is made of an inorganic insulating material such as silicon oxide (SiO x ) or silicon nitride (SiN x ).  
         [0122]    Further, as shown in FIGS. 9A and 9B, a semiconductor pattern group including an active layer  148  and the ohmic contact layer  150 , and a second conductive pattern group including the data line  104 , the drain electrode  112 , the pixel electrode  114 , the data pad  130  and the storage electrode  122  are formed on the gate insulating film  146  using the second mask process.  
         [0123]    There will be explained the second mask process in detail with reference to FIGS. 10A to  10 F.  
         [0124]    As shown in FIG. 10A, on the gate insulating film  146 , a first semiconductor layer  147 , a second semiconductor layer  149 , a first and a second source/drain metal layer  154  and  156  are sequentially provided by deposition techniques such as the plasma enhanced chemical vapor deposition (PECVD) and the sputtering, etc. Herein, the first semiconductor layer  147  is made of an amorphous silicon that an impurity is not doped and the second conductor layer  149  is made of amorphous silicon that an impurity of a N type or P type is doped. Any one of the first and the second source/drain metal layers  154  and  156  is made of any metal that has a relatively high strength and corrosion resistance such as a titanium (Ti) and a tungsten (W), whereas another metal layer is made of any metal such as an aluminum (Al) system metal, a molybdenum (Mo) and a copper (Cu).  
         [0125]    Thereafter, a photo-resist film is formed on the second source/drain metal layer  156  and then a second mask  160  used for a partial exposure is arranged on the lower substrate  145  as shown in FIG. 10B. The second mask  160  comprises a mask substrate  162  which is of a transparent material, a cut-off part  164  formed on a cut-off region P 2  of the mask substrate  162  and a diffractive exposure part  166  (or a semi-transmitting part) formed on a partial exposure region P 3  of the mask substrate  162 . Herein, a region in which the mask substrate  162  is exposed becomes an exposure region P 1 . The photo-resist film is exposed using the second mask  160  as set forth above and then developed, to thereby form the photo-resist pattern  168  which has a stepped part in the cut-off region P 2  and the partial exposure region P 3  corresponding to the diffractive exposure part  166  and cut-off part  164  of the second mask  160 . That is, the photo-resist pattern  168  formed in the partial exposure region P 3  has a second height H 2  that is lower than a first height H 1  of the photo-resist pattern  168  formed in the cut-off region P 2 .  
         [0126]    Subsequently, the first and the second source/drain metal layer  154  and  156  are patterned by a wet etching process using, as a mask, the photo-resist pattern  168 , so that the second conductive pattern group including the data line  104 , the drain electrode  112  connected to the data line  104 , the pixel data  114 , the storage electrode  122  and the data pad  130  is formed as shown in FIG. 10C.  
         [0127]    Thereafter, the first semiconductor layer  147  and the second semiconductor layer  149  are patterned by a dry etching process using the photo-resist pattern  168  as a mask to thereby provide the ohmic contact layer  150  and the active layer  148  along the second conductive pattern group as shown in FIG. 10D. Next, the photo-resist pattern  168  formed with the second height H 2  in the partial exposure region P 3  is removed by the ashing process using an oxygen (O 2 ) plasma, whereby the photo-resist pattern  168  formed with the first height H 1  in the cut-off region P 2  has a lowered height. The partial exposure region P 3 , that is, the first and the second source/drain metal layers  154  and  156  formed at channel portion of the thin film transistor are removed by etching process using the photo-resist pattern  168 . For instance, in case where the second source/drain metal layer  156  is made of a molybdenum Mo and the first source/drain metal layer  154  is made of a titanium Ti, the second source/drain metal layer  156  is removed in the channel portion by a dry etching process and the first source/drain metal layer  154  is removed by a wet etching process in the channel portion. On the contrary, in case where the second source/drain metal layer  156  is made of a titanium Ti and the first source/drain metal layer  154  is made of a molybdenum Mo, the second source/drain metal layer  156  is removed by a wet etching process in the channel portion and the first source/drain metal layer  154  is removed by a dry etching process in the channel portion. Accordingly, the drain electrode  112  is separated from the data line  104  including the source electrode. Thereafter, the ohmic contact layer  150  is removed by a dry etching process using the photo-resist pattern  168  to thereby expose the active layer  148 .  
         [0128]    Further, a remainder of the photo-resist pattern  168  left on the second conductive pattern group is removed by a stripping process as shown in FIG. 10E.  
         [0129]    Thereafter, a passivation film  152  is formed on the gate insulating film  146  having the second conductive pattern group thereon. The passivaion film  152  is made of an inorganic insulating material such as the gate insulating film  146  or an organic insulating material having a small dielectric constant such as an acrylic organic compound, BCB (benzocyclobutene) or PFCB (perfluorocyclobutane), etc.  
         [0130]    Subsequently, an aliment film (not shown) is formed on the passivation film  152  in a display area except for a pad region in which the gate pad  124 , the data pad  130  and the common pad  136  are located on the thin film transistor having the passivation film  152 .  
         [0131]    [0131]FIGS. 11A and 11B are a plan view and a sectional view for representing a pad opening process exposing a pad using a color filter array substrate as a mask, respectively.  
         [0132]    As shown in FIG. 11A and FIG. 11B, the gate pad  124 , the common pad  136  and data pad  130  is exposed using the pad opening process.  
         [0133]    The pad opening process will be described in detail with reference to FIGS. 12A to  12 B.  
         [0134]    On the lower substrate  145 , the thin film transistor array substrate having the thin film transistor array thereon formed using the first and the second mask process and the color filter array substrate formed using a separate process are prepared, and combined and then the thin film transistor array substrate and the color filter array substrate  212  are combined using a sealant  250  as shown in FIG. 12A. In this case, the color filter array substrate  212  is combined with the thin film transistor array substrate so as to expose a pad region where the gate pad  124 , the data pad  130  and the common pad  136  are formed on the thin film transistor array substrate.  
         [0135]    Subsequently, the passivation film  152  and the gate insulating film  146  are patterned in the way of an etching process using the color filter array substrate as a mask such that the gate pad  124 , the common pad  130  and the data pad  130  are exposed as shown in FIG. 12B.  
         [0136]    The gate pad  124 , the data pad  130  and the common pad  136  have structure in which a metal layer with a high strength and corrosion resistance. In this case, the gate pad  124 , the data pad  130  and the common pad  136  have two structures as shown in FIGS. 13 and 14.  
         [0137]    For instance, in case where the first gate metal layer  142  of a lower portion is made of a titanium Ti and the second gate metal layer  144  of an upper portion is made of a molybdenum Mo, the gate pad  124  and the common pad  136  are consisted of only the first gate metal layer  142  of the lower portion as shown in FIG. 13. This is because the second gate metal layer  144  of the upper portion is removed during the pad opening process.  
         [0138]    On the contrary, in case where the first gate metal layer  142  of the lower portion is made of a molybdenum Mo and the second gate metal layer  144  of the upper portion is made of a titanium Ti, the gate pad  124  and the common pad  136  have a double-layer structure of metal layers in which the first and the second gate metal layers  142  and  144  are stacked as shown in FIG. 14. Also, the gate pad  124  and the common pad  136  have structure in which the gate metal layer  144  of the upper portion is exposed through the use of the pad opening process.  
         [0139]    Further, in case where the first source/drain metal layer  154  of the lower portion is made of a titanium Ti and the second source/drain metal layer  156  of the upper portion is made of a molybdenum Mo, the data pad  130  is consisted of only the first source/drain metal layer  154  of the lower portion as shown in FIG. 13. This is because the second source/drain metal layer  156  is removed during the pad opening process.  
         [0140]    On the contrary, in case where the first source/drain metal layer  154  of the lower portion is made of a molybdenum Mo and the second source/drain metal layer  156  is made of a titanium Ti, the data pad  130  has a double-layer structure of metal layers in which the first and the second source/drain metal layers  154  and  156  are stacked as shown in FIG. 14. Also, the data pad  130  has structure in which the source/drain metal layer  156  of the upper portion is exposed through the use of the pad opening process.  
         [0141]    As shown in FIG. 15A and FIG. 15B, the exposed pads  124  and  130  of the pad region on the lower substrate  145  are directly contacted with the drive ICs  350  and  356  via the bump  260  and  286 . That is, the output terminal  262  of the gate drive IC  350  is contacted with the gate pad  124  via the output bump  260  and the output terminal  284  of the data drive IC  356  is contacted with the data pad  130  via the output bump  268 . In this case, the gate pad  124  and the data pad  130  have the exposed structure of metal layer that has a relatively high strength and corrosion resistance are directly contacted with their corresponding drive ICs  350  and  356  such that corrosion of the exposed metal layer is prevented.  
         [0142]    On an area except for a COG connector  358  of the lower substrate  145  on which the gate drive IC  350  and the data drive IC  356  are mounted, a first package mold material  252  is formed as shown in FIG. 16A and FIG. 16B. The first package mold material  252  is formed to partially capsulate the signal supplying line  208 , the gate drive IC  350 , the gate pad  124 , the data drive IC  356  and the data pad  130  as exposed. Otherwise the first package mole material is formed to capsulate, an entirely exposed area on lower substrate  145  not being overlapped with the upper substrate  200 , that is, the signal supplying line  208 , the gate drive IC  350  and the data drive IC  356 .  
         [0143]    Subsequently, the COG connector  358  connected to the signal supplying line  208  is connected with the FPC  354  using the TAB process as shown in FIG. 17A and FIG. 17B. That is, an input pad of the FPC  354  is connected to the PCB  352  and an output pad of the FPC  354  is connected to the COG connector  288 . Further, any one of output pads  282  of the FPC  354  is connected to the common pad  136  using the ACF  182  including the conductive ball  184  to thereby supply the reference voltage for driving the liquid crystal to the common line  116 . The FPC  354  supplies gate control signals and power source signals from timing controller and a power source portion on the PCB  352  to the corresponding drive ICs  350  and  356 .  
         [0144]    Next, a second package mold material  372  is formed at a boundary portion of the COG connector  358  and the FPC  354  and a boundary of the lower substrate  145  and the FPC  354  as shown in FIG. 18A and FIG. 18B. The second package mold material  372  is packaged for protecting the boundary portion of the COG connector  358  and the FPC  354  as shown in FIG. 18A and the boundary of the lower substrate  145  and the FPC  354  as shown in FIG. 18B.  
         [0145]    As described above, according to the thin film transistor array substrate of horizontal electric field applying type and the manufacturing method of the present invention, the pixel electrode is formed as an identical metal to the drain electrode, and the pads have the structure wherein a metal layer having a high strength and corrosion resistance is exposed in order to prevent the defect caused by the opening.  
         [0146]    Further, the thin film transistor array substrate of horizontal electric field applying type and the fabricating method of the present invention combine the thin film transistor array substrate formed using the two-round mask process and the color filter array substrate and then expose the pad to contact with the drive IC using the pad opening process. Accordingly, according to the thin film transistor array substrate of horizontal electric field applying type and the fabricating method thereof according to the present invention, it is possible to manufacture the thin film transistor array substrate using the two-round mask process and therefore to simplify the structure and process of the thin film transistor array substrate, to thereby reduce the manufacturing cost and improve the manufacture yield.  
         [0147]    Moreover, according to the liquid crystal display of horizontal electric applying type and the manufacturing method the present invention, a drive IC mounted on a substrate by a COG system directly is directly connected to a pad, the drive IC and the pad as connected are packaged using a mold material. Accordingly, it is possible to protect the drive IC and the pad from exterior substances and to prevent a corrosion of an entirely exposed signal supplying line and a side exposed pad.  
         [0148]    Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.

Technology Classification (CPC): 6