Abstract:
A method and structure for reducing the resistivity of a repair line in an active panel includes a repair line made of a gate material and a method for manufacturing the same. All parts of the repair line comprise low resistivity metal such as aluminum or copper so that a detoured data signal is not delayed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a thin film transistor panel (or TFT panel) of a liquid crystal display device (or LCD), and more specifically, to a method for reducing the resistivity of a repair line in the TFT panel (or active panel). 
     2. Description of the Background Art 
     A conventional liquid crystal display device comprises an active panel and a driving circuit. The active panel, as shown in FIG. 1, comprises an upper panel  2  and a lower panel  1  which are arranged to face each other and to be joined together with a liquid crystal material  25  located therebetween. The upper panel  2  comprises a polarizing panel  20 , a transparent substrate  22 , a color filter  23  and a common electrode  24  all of which are disposed on the transparent substrate  22 . The lower panel  1  comprises a polarizing panel  20 , a transparent substrate  21 , a plurality of gate lines  14  disposed on the transparent substrate  21 , a plurality of data lines  15  which are perpendicularly crossed with the gate lines  14  and a pixel electrode  26  and a thin film transistor  16  which are disposed at the intersection portion of the gate lines  14  and the data lines  15 . Pads (not shown in FIG. 1) are formed at the ends of the gate lines  14  and the data lines  15  and have a width that is larger than a width of the respective gate and data lines. The lower panel  1  is divided into a displaying area in which the pixel electrode  26  and the thin film transistor  16  are formed and a pad area in which pads connected to the ends of the gate lines  14  and the data lines  15  are formed. 
     The thin film transistor comprises a gate electrode  31  connected to the gate line  14 , a source electrode  32  connected to the data line  15  and a drain electrode  33  connected to the pixel electrode  26 . Generally, the gate electrode  31  and the gate line  14  are formed during the same processing step. Also, the data line  15 , the source electrode  32  and the drain electrode  33  are formed during the same processing step. 
     The manufacturing process of the TFT is described with reference to FIGS. 2 a - 2   c . At first, the gate electrode  31  is formed on the transparent substrate  21  of the lower panel  1 . An oxidation layer  37  is then formed on the gate electrode  31 . Then, an insulating layer  30  is formed so as to cover the gate electrode  31  and the oxidation layer  37 . A semiconductor layer  35  is formed on the insulating layer  30  so as to cover the gate electrode  31 . An impurity doped semiconductor layer  34  is formed on the semiconductor layer  35 . After that, the source electrode  32  and the drain electrode  33  are formed on the doped semiconductor layer  34  and the insulating layer  30 . The doped semiconductor layer  34  is patterned by using the source electrode  32  and the drain electrode  33  as a mask. Therefore, the portion of the doped semiconductor layer  34  disposed between the source electrode  32  and the drain electrode  33  is removed. Finally, a passivation layer  36  covering the resulting substrate  21  is formed so that the TFT is completed. The gate line  14  and the gate pad (not shown) are formed at the same time that the gate electrode  31  is formed. The data line  15  and the data pad  40  are formed at the same time that the source electrode  32  and the drain electrode  33  are formed. 
     In order to increase the resolution of the LCD, many data lines are required. If one data line is broken, then the whole panel can not be used. So, it is necessary prepare an additional line, called a repair line, for repairing a broken line and preventing a broken line from rendering the whole panel unusable. Generally, the repair line is disposed around a periphery of the active panel. The horizontal portion of the repair line is disposed at a location where the gate lines intersect the gate pads and the vertical portion of the repair line is disposed at a location where the data lines intersect the data pads. 
     FIG. 3 a  shows the active panel having the data pads  40 , data lines  15  and the repair line  60  in detail. FIG. 3 b  shows another diagram of the active panel according to the conventional art. The repair line  60  comprises a gate line crossing portion  60   a  and a data line crossing portion  60   b . The data line crossing portion  60   b  of the repair line  60  is formed at the same time that the gate line  14  is formed and the gate line crossing portion  60   a  of the repair line  60  is formed at the same time that the data line  15  is formed. These two portions of the repair line  60  are connected to each other through a contact hole  51 . Referring to the FIG. 3 c  showing a cross section along the cutting line A—A of FIG. 3 a , the manufacturing process of making and connecting the two portions of the repair line  60  in the conventional art is explained. 
     At first, the data line crossing portion  60   b  of the repair line  60  is formed at the same time that the gate electrode  31 , the gate line  14 , the gate pad (not shown) and a common line  70  are formed. Here, the common line  70  which preferably comprises an anti-electrostatic ground line, prevents an electrostatic capacitance from being formed when the gate lines are separated from each other. Then, a gate insulation layer  30  is deposited thereon. The gate insulation layer  30  has a contact hole  51  exposing an end portion of the data line crossing portion  60   b  of the repair line  60 . Then the gate line crossing portion  60   a  of the repair line  60  is formed at the same time that the source electrode  32 , the drain electrode  33 , the data line  15  and the data pad  40  are formed. The gate line crossing portion  60   a  of the repair line  60  is connected to the exposed portion of the data line crossing portion  60   b  of the repair line  60  through the contact hole  51 . 
     If a data line  15  is broken by a defect  43 , then the intersection point  45  of the data line  15  and the repair line  60  is connected. So, the data signal applied to the data line  15  having a defect  43  is detoured through the repair line  60 . Hence the broken data line  15  appears to be repaired. 
     The data line crossing portion  60   b  of the repair line  60  comprises the same material of the gate electrode  31  and the gate line crossing portion  60   a  of the repair line  60  comprises the same material as that of the source electrode  32  and the drain electrode  33 . So, the data line crossing portion  6   b  comprises a low resistance metal such as aluminum or copper. On the other hand, the gate line crossing portion  60   a  comprises a high resistance conductive material such as chromium or indium-tin-oxide (or ITO). Therefore, the resistance of the repair line  60  is related to the sum of the resistance of the two contacts, i.e., the gate material and source material, R G +2R c +R S/D , where R G  is the resistivity of the gate material, R c  is a contact resistance at the data line crossing portion  60   b  and the gate line crossing portion  60   a  of the repair line  60  and R S/D  is the resistivity of the source material. Hence, the resistance of the repair line  60  is higher than any other part of the active panel. 
     In this structure, if a data line  15  which is located far from the repair line  60  has a defect  43 , then the data line signal traveling the detoured course is significantly delayed by the high resistance of the repair line  60  so that the repair line  60  does not properly work as a repair line. As a result, a repairing area provided by the repair line  60  is limited to only an area located very near to the repair line  60 . 
     SUMMARY OF THE INVENTION 
     To overcome the problems described above, the preferred embodiments of the present invention provide a repair line having a low resistance and having an unlimited or maximum repairing area provided by the low resistance repair line. 
     According to a preferred embodiment of the present invention, an active panel includes a repair line made of a gate material and a method for manufacturing the same. In the preferred embodiments of the present invention, all parts of the repair line are formed when the gate electrode is formed. Therefore, the repair line comprises low resistance metal such as Al, AlNd, Mo and Cu so that any signal delay occurring at the detoured data line is significantly reduced. 
     According to preferred embodiments of the present invention, an active panel comprises a display area having a common line and a gate line, a repair line surrounding the display area and crossing the common line, a pad area including a data pad and a gate pad which are located at an area outside of the repair line, wherein the repair line includes a material used to form the gate line. 
     Other features and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention which refers to the accompanying drawings, wherein like reference numerals indicate like elements to avoid duplicative description. 
    
    
     BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS 
     FIG. 1 is a perspective view illustrating a conventional active panel; 
     FIGS. 2 a - 2   c  are cross-sectional views illustrating a conventional method for manufacturing a thin film transistor in an active panel; 
     FIGS. 3 a  and  3   b  are plan views showing the conventional active panel having a repair line, a gate line and a gate pad. 
     FIG. 3 c  provides cross sectional views showing the conventional method for manufacturing the repair line. 
     FIGS. 4 a  and  4   b  are plan views showing an active panel having a repair line, a gate line and a gate pad according to a first preferred embodiment of the present invention. 
     FIG. 4 c  provides cross sectional views showing a method for manufacturing the repair line according to the first preferred embodiment of the present invention. 
     FIGS. 5 a  and  5   b  are plan views showing an active panel having a repair line, a gate line and a gate pad according to the second preferred embodiment of the present invention. 
     FIG. 5 c  provides cross-sectional views illustrating a method of manufacturing a repair line according to the second preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 4 a  showing a plan view of an active panel, FIG. 4 b  showing another diagram of FIG. 4 a  and FIG. 4 c  showing a cross sectional view along the section line B—B in FIG. 4 a , the first preferred embodiment of the present invention will be explained in detail. 
     A repair line  110  is preferably formed at the same time that a gate electrode (not shown), a gate line  114  and a gate pad (not shown) are formed using a low resistance metal such as Al, AlNd, Mo and Cu. The repair line  110  comprises a horizontal portion  110   b  and a vertical portion  110   a . The horizontal portion  110   b  is disposed at a location at which the data line  115  is connected to the data pad  100 . The vertical portion  110   a  is disposed at an area outside of a common line (anti-electrostatic ground line)  120  of the gate line  114  and gate pad (not shown). The gate line  114  is connected to the common line  120  through an anti-electrostatic circuit  220 , as shown in FIG. 4 a.    
     Thus, all portions of the repair lines  110  comprise the low resistance material and all repair lines  110  are made completely of the same low resistance material. Therefore, if a data line  115  is broken by a defect  143 , an intersection point  145  of the data line  115  and the repair line  110  is connected. Generally, a preferred connection method is to weld the intersection point  145  using a laser beam. So, the data signal applied to the data line  115  having a defect  143  is detoured through the repair line  110 . As a result, the broken data line  115  is repaired, as shown in FIG. 4 b.    
     Because the repair line  110  is formed at the same time that the gate line  114  and the common line  120  are formed, and the repair line  110  is disposed outside of the common line  120 , it is important how the repair line  110  is insulated with the common line  120 . As is shown in FIG. 4 a , the portions  110   a  and  110   b  of the repair line are divided into two parts and connected with a connector  160  through contact holes  151  and  153 . In this preferred embodiment, it is preferable that the repair line  110  is divided into a horizontal portion  110   b  and a vertical portion  110   a  in the same layer. After the gate insulating layer  210  is deposited, contact holes  151  and  153  exposing some of the two portions  110   b  and  110   a  of the repair line  110 , respectively, are formed and as a result, the two portions of the repair line are connected by a connector  160  comprising a source material, as shown in FIG. 4 c.    
     In a second preferred embodiment shown in FIGS. 5 a - 5   c , a repair line  110  is preferably formed at the same time that a gate electrode (not shown), a gate line  114  and a gate pad (not shown) are formed using a low resistance metal such s Al, AlNd, Mo and Cu. The repair line  110  comprises a horizontal portion  110   b  and a vertical portion  110   a . The horizontal portion  110   b  is disposed at a location at which the data line  115  is connected to the data pad  100 . The vertical portion  110   a  is disposed at an area outside of a common line (anti-electrostatic ground line)  120  of the gate line  114  and gate pad (not shown). The repair line  110  is formed as a single integral body, instead of two separate bodies, so that the common line  120  is divided into two portions and connected with a connector  160  through contact holes  151  and  153 , as shown in FIG. 5 a.    
     Thus, all portions of the repair lines  110  comprise the low resistance material and all repair lines  110  are made completely of the same low resistance material. Therefore, if a data line  115  is broken by a defect  143 , then an intersection point  145  of the data line  115  and the repair line  110  is connected. Generally, a preferred connection method is to weld the cross point  145  using a laser beam. So, the data signal applied to the data line  115  having the defect  143  is detoured through the repair line  110 . As a result, the broken data line is repaired, as shown in FIG. 5 b.    
     In this preferred embodiment, it is suggested that the common line  120  is divided into two parts and formed at the same layer of the repair line  110 . In that case, the repair line  110  comprises a horizontal portion  110   b  and a vertical portion  110   a  which are formed as an integral single body in the same layer. After the gate insulating layer  210  is deposited, contact holes  151  and  153  exposing some of the two portions of the common line  120 , respectively, are formed and as a result, the two portions of the common line  120  are connected by a connector  160  comprising a source material, as shown in FIG. 5 c.    
     The preferred embodiments of the present invention provide a repair line including a low resistance material used for a gate electrode, a gate line and a gate pad. Therefore, any delay in transmitting signals caused by the repair line replacing the broken data line is greatly reduced. Hence, the active panel including such a repair line has no limit on a repairing area as opposed to the conventional art in which the repair line comprises source material such as chromium or ITO having a higher resistance than a gate material. 
     Although the present invention has been explained with reference to preferred 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 preferred embodiments described herein, 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.