Abstract:
A liquid crystal display (LCD) device has improved adhesion between a tape carrier package and a liquid crystal panel and the LCD device includes an organic insulating layer for increasing the aperture ratio. The LCD includes electrode pads provided on a substrate, semiconductor patterns for preventing etching of the portions of the gate insulating layer that are in contact with the electrode pads, and transparent electrodes for protecting the electrode pads and in contact with the semiconductor patterns. The LCD eliminates the organic protective layer positioned around the pads, thereby strengthening the adhesion between the liquid crystal panel and the TCP.

Description:
This application claims the benefit of Korean Patent Application No. P99-18569, filed on May 21, 1999, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a liquid crystal display (LCD) and more particularly, to an LCD that has stronger adhesion between a tape carrier package (TCP) and an LCD panel having an organic insulating layer, and a method for manufacturing the same. 
     2. Description of the Related Art 
     Generally, an LCD controls the light transmissivity of liquid crystal cells in response to a video signal, thereby displaying a picture that reflects the video signal that is transmitted to the liquid crystal panel in which liquid crystal cells are arranged in a matrix pattern. To achieve this result, the LCD includes drive integrated circuits (ICs) for driving the liquid crystal cells that are arranged in the matrix pattern on the liquid crystal panel. The drive ICs are manufactured in chip form. The drive IC chips are loaded onto the TCP when the LCD is implemented in a Tape Automated Bonding (TAB) system. Alternatively, if the LCD is implemented in a Chips On Glass (COG) system, the drive IC chips are mounted on the liquid crystal panel. The drive IC chips that are implemented in the COG system are electrically connected to a pad portion on the liquid crystal panel by the TCP. 
     FIG. 1 shows a surface of a conventional liquid crystal panel. The liquid crystal panel  2  has a structure that includes a lower substrate  4  and an upper too, substrate  6 , which are bonded so as to oppose each other. The liquid crystal panel  2  also includes a display portion  8  that is provided with liquid crystal cells arranged in a matrix, and a gate pad portion  12  and a data pad portion  14  arranged such that each is connected between the drive IC chips (not shown) and the display portion  8 . The display portion  8  includes gate lines and data lines arranged on the lower substrate  4  such that they intersect each other, thin film transistors for switching the liquid crystal cells located at the intersections of the gate and data lines, and pixel electrodes that are each connected to the thin film transistors for driving the liquid crystal cells. Also, the display portion  8  has color filters separated by a black matrix on the upper substrate  6  that are the size of a cell region, and a transparent common electrode coated on the surface of the color filters. The lower substrate  4  and the upper substrate  6  are separated from each other by spacers to define a cell gap so that the cell gap. can be filled with liquid crystal material. Also, the lower substrate  4  and the upper substrate  6  are bonded to each other by a sealing material  10  that surrounds the display portion  8 . The gate pad portion  12  and the data pad portion  14  are provided at the edges of the lower substrate  4  which are not overlapped with the upper substrate  6 . The gate pad portion  12  applies a gate driving signal from the gate drive IC chips, which are included in the drive IC chips, to the gate lines of the display portion  8 . The data pad portion  14  transmits a video signal from the data drive IC chips, which are included in the drive IC chips, to the data lines of the display portion  8 . 
     The liquid crystal panel  2  having the above-described structure uses a protective layer which is disposed on the entire surface of the lower substrate  4  to protect the pixel electrodes and the thin film transistors. The conventional protective layer is an inorganic layer made from SiNx, SiOx and other similar materials. In order to minimize the coupling effect caused by parasitic capacitance, the pixel electrodes and the data lines that are opposite each other have the inorganic protective layer as their center, and must be apart from each other by a constant distance, for example, about 3 to 5 μm. This is required because the inorganic protective layer has a high dielectric constant. Due to this, the pixel electrode, which determines the aperture ratio, must be small in size. 
     Conventionally, to make the pixel electrode bigger so that the aperture ratio is greater, an organic material such as benzocyclobutene (BCB), which has a low dielectric constant, is used as the protective layer. For exarmple, in U.S. Pat. No. 5,798,812, there is provided an organic insulating film that covers the pixel area. and the pad area portions of the LCD. Because the organic protective layer has a dielectric constant lower than that of the inorganic protective layer by about 2.7, the pixel electrode can be overlapped with the data line. Thus, the pixel electrode can be enlarged by the amount of overlap between the pixel electrode and the data line so that the aperture ratio of the liquid crystal cell is increased. 
     The LCD of the TAB system allows the TCP that mounts the drive IC chips to contact the gate and data pad portions. The TAB process forces the TCP to be repeatedly bonded to and then separated from the data and gate pad portions of the liquid crystal panel. In order to prevent the metallic electrodes that are used as the data pads from being damaged due to the repeated bonding and separation between the TCP and the data pad portion of the liquid crystal panel, the data pads that are included in the data pad portion and defined by metallic electrodes are connected to the TCP via transparent electrodes. However, the organic protective layer is weakly bonded with the gate insulating layer and therefore separates easily from the gate insulating layer. As a result, the transparent electrode on the organic protective layer is also easily separated. This problem will be described hereinbelow with reference to FIGS. 2 to  5 B. 
     FIG. 2 is a detailed view of a part of the gate pad portion  12  of FIG.  1 . FIG. 3A is a cross-sectional view representing the gate pad portion taken along the IIIA-IIIA′ line as shown in FIG.  2 . FIG. 3B is a cross-sectional view of the gate pad portion  12  taken along the IIIB-IIIB′ line as shown in FIG.  2 . Referring to FIGS. 2,  3 A and  3 B, the gate pads  16  are provided on a lower glass substrate  22  together with the gate lines that are included in the display portion all at the same time. A gate insulating layer  24  and an organic protective layer  26  are sequentially disposed on the entire surface of the lower glass substrate  22  having the gate pads  16  thereon. The gate insulating layer  24  and the organic protective layer  26  are patterned so as to form holes  18  at each of the gate pads  16 . The holes  18  that are located at each gate pad  16  allow the gate pads  16  to be exposed. Transparent electrode patterns  20  are then formed on the organic protective layer  26  such that the transparent electrode patterns  20  are each connected to the corresponding gate pad  16  through the corresponding hole  18 . 
     Note that the organic protective layer  26  is weakly bonded with the gate insulating layer  24  and so is separated easily from the gate insulating layer  24  when the TCP is separated from the gate pad portion  12  on the liquid crystal panel. Also, the adhesion between the organic protective layer  26  and the gate insulating layer  24  is further weakened by the holes  18  that are defined in the organic protective layer  26  and the gate insulating layer  24  so that almost all of the organic protective layer  26  becomes separated when the TCP is separated from the gate pad portion  12 . 
     Therefore, the gate pad portion  12  does not have a uniform surface due to the separation of the organic protective layer  26 . Because of this, the TCP becomes weakly bonded with the gate pad portion  12  when it is re-bonded with the gate pad portion  12  so as to decrease the connection area causing increased resistance. Further, the transparent electrode  20  is also separated from the gate pad portion  12  when the organic protective layer  26  becomes separated and exposes the gate pads  16 . Thus, the gate pads  16  are easily damaged or oxidized. 
     FIG. 4 is a detail view of a part of the data pad portion  14  of FIG.  1 . FIG. 5A is a cross-sectional view representing the data pad portion  14  taken along the VA-VA′ line of FIG. 4, and FIG. 5B is a cross-sectional view of the data pad portion  14  taken along the VB-VB′ line of FIG.  4 . Data pads  28 , as shown in FIGS. 4,  5 A and  5 B, are provided on the gate insulating layer  24  of a lower glass substrate  22  together with the data lines (not shown) all at the same time. A semiconductor layer  30  under the data pad  28  is extended to the data line. The organic protective layer  26  is disposed on the entire surface of the gate insulating layer  24  having the data pads thereon. The organic protective layer  26  is patterned so as to define holes  18  at each of the data pads  28 . The holes  18  defined at each of the data pads  28  allow the data pads  28  to be exposed. Transparent electrode patterns  20  are defined on the organic protective layer  26  such that the electrode patterns  20  are each connected to the corresponding data pad  28  through the corresponding hole  18 . 
     Note that the organic protective layer  26  is weakly bonded with the gate insulating layer  24  and therefore separates easily from the gate insulating layer  24  when the TCP is separated from the data pad portion  14  on the liquid crystal panel. Also, the adhesion between the organic protective layer  26  and gate insulating layer  24  is further weakened by the holes  18  that are defined on the organic protective layer  26  so that almost all of organic protective layer  26  becomes removed during this process. 
     Therefore, the data pad portion  14  has a surface that is non-uniform due to the separation of the organic protective layer  26 . Because of this, the TCP becomes weakly bonded with the data pad portion  14  when it is re-bonded with the data pad portion  14  so as to decrease the connection area causing increased resistance. Further, the transparent electrode  20  is also separated from the data pad portion  14  along with the organic protective layer  26  so that the data pads  28  become exposed. Thus, the data pads  28  are easily damaged or oxidized. 
     SUMMARY OF THE INVENTION 
     To overcome the problems described above, preferred embodiments of the present invention provide an LCD that has stronger adhesion between the TCP and a liquid crystal panel while providing a high aperture ratio by using an organic insulating layer. 
     A preferred embodiment of the present invention includes a substrate, electrode pads on the substrate, transparent electrodes arranged on the electrode pads, and a semiconductor layer disposed between the substrate and the transparent electrodes, wherein the semiconductor layer is in contact with the transparent electrodes. 
     Another preferred embodiment of the present invention includes a glass substrate, a gate insulating layer on the glass substrate, electrode pads on the glass substrate, transparent electrodes on the electrode pads for protecting the electrode pads, a semiconductor layer on the gate insulating layer for preventing an etching of a gate insulating layer that is in contact with the electrode pads, and wherein the semiconductor layer is in contact with the transparent electrodes. 
     According to another preferred embodiment of the present invention a method for manufacturing an LCD includes the steps of providing a glass substrate, forming gate pads on the glass substrate, overlaying a gate insulating layer on the entire surface of the glass substrate and forming holes exposing the gate pads, forming data pads on the gate insulating layer, disposing a semiconductor layer on the gate insulating layer, wherein the semiconductor layer is at least partially beneath the data pads, and wherein the semiconductor layer is at least partially overlapped with the the gate pads, coating an organic protective layer on the entire surface of the glass substrate, sequentially etching the organic protective layer and the gate insulating layer in an area of the gate pads and the data pads, wherein the organic protective layer is removed from the area of the gate and data pads, and forming transparent electrodes on the data and gate pads for protecting the data and gate pads. 
     Thus, the present invention described herein makes possible the advantages of having stronger adhesion between the TCP and the pad portions of a liquid crystal panel while improving the aperture ratio of the LCD. 
     Other features, elements and advantages will be described in detail below with reference to preferred embodiments of the present invention and the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS 
     The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus do not limit the present invention and wherein: 
     FIG. 1 is a plan view of a conventional LCD; 
     FIG. 2 is a plan view representing in detail a part of the gate pad portion as shown in FIG. 1; 
     FIG. 3A is a cross-sectional view showing the gate pad portion taken along the IIIA-IIIA′ line of FIG. 2; 
     FIG. 3B is a cross-sectional view showing the gate pad portion taken along the IIIB-IIIB′ line of FIG. 2; 
     FIG. 4 is a plan view representing in detail a part of the data pad portion as shown in FIG. 1; 
     FIG. 5A is a cross-sectional view showing the data pad portion taken along the VA-VA′ line of FIG. 4; 
     FIG. 5B is a cross-sectional view showing the data pad portion taken along the VB-VB′ line of FIG. 4; 
     FIG. 6 is a plan view representing in detail a part of gate pad portion included in a LCD according to a preferred embodiment of the present invention; 
     FIG. 7A is a cross-sectional view showing the gate pad portion taken along the VIIA-VIIA′ line of FIG. 6; 
     FIG. 7B is a cross-sectional view showing the gate pad portion taken along the VIIB-VIIB′ line of FIG. 6; 
     FIG. 8 is a plan view representing in detail a part of data pad portion included in a LCD according to another preferred embodiment of the present invention; 
     FIG. 9A is a cross-sectional view showing the data pad portion taken along the IXA-IXA′ line of FIG. 8; and 
     FIG. 9B is a cross-sectional view showing the data pad portion taken along the IXB-IXB′ line of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention for strengthening the adhesion between a TCP and pad portions of a liquid crystal panel will be described in detail with reference to FIGS. 6 to  9 B. 
     FIG. 6 is a detailed plan view representing a part of the gate pad portion that is included in an LCD according to a preferred embodiment of the present invention. FIG. 7A is a cross-sectional view showing the gate pad portion taken along the VIIA-VIIA′ line of FIG. 6, and FIG. 7B is a cross-sectional view showing the gate pad portion taken along the VIIB-VIIB′ line of FIG.  6 . 
     Gate pads  16 , as shown in FIGS. 6,  7 A, and  7 B, are provided on a lower glass substrate  22  together with the gate lines of a display portion (not shown) preferably all at the same time. A gate insulating layer  24  is disposed on the entire surface of the lower glass substrate  22  so as to mount the gate pads  16  thereon. The gate insulating layer  24  is patterned so as to define holes  18  which are positioned at each of the gate pads  16 . The holes  18 . allow the gate pads  16  to be exposed. Then, a semiconductor pattern  32 , preferably made of amorphous silicon, is disposed on the gate insulating layer  24  and around each of the holes  18 . The semiconductor pattern  32  preferably has a substantially ring shaped configuration arranged such that an edge of the gate pad  16  is overlapped by the semiconductor pattern  32  and the gate insulating layer  24 . Next, an organic protective layer is coated on the entire surface of the gate insulating layer  24  so as to locate the semiconductor pattern  32  thereon. The organic protective layer is then removed from the gate pad portion of the liquid crystal panel via patterning. The gate insulating layer  24  is also patterned via an etching process. 
     When the gate insulating layer  24  is etched, the semiconductor pattern  32  functions as an etching prevention layer to prevent the undercutting of the gate insulating layer  24 . Note that if the width of the semiconductor pattern  32  is too narrow, the gate insulating layer  24  will be undercut at the etched area. If this occurs, the gate pad will be damaged in the TAB process and the transparent electrode that is to be formed after the etching process may be opened due to a step that is created by the semiconductor pattern  32  and the etched gate insulating layer  24 . Thus, the width of the semiconductor pattern  32  must be set appropriately to prevent undercutting of the gate insulating layer  24 . Finally, the transparent electrode  20  is formed on each semiconductor pattern  32 . The transparent electrodes  20  protect the gate pads  16 . The gate pad portion with the above-described structure eliminates the need for the organic protective layer and the gate insulating layer  24  around the gate pads  16 , and partially exposes the surface of the lower glass substrate  22 , as shown in FIG.  7 B. 
     Accordingly, the gate pad portion prevents separation of the transparent electrode  20  due to weak adhesion between the organic protective layer and the gate insulating layer  24  when the TAB process is repeated. Also, an Anisotropic Conductive Film (ACF) (not shown) to bind the TCP to the gate pad portion is in contact directly with the lower glass substrate  22 . Thus, the adhesion between the gate pad portion and the TCP remains very strong. 
     FIG. 8 is a detailed plan view representing a part of data pad portion that is included in an LCD according to another preferred embodiment of the present invention. FIG. 9A is a cross-sectional view showing the data pad portion taken along the IXA-IXA′ line of FIG. 8, and FIG. 9B is a cross-sectional view showing the data pad portion taken along the IXB-IXB′ line of FIG.  8 . Referring to FIGS. 8,  9 A, and  9 B, the data pad portion includes a semiconductor pattern  32 , preferably made of amorphous silicon, on the gate insulating layer  24  and disposed on the lower glass substrate  22 . Each semiconductor pattern  32  preferably has a substantially ring shaped configuration similar to that of the gate pad portion. Also, the semiconductor pattern  32  that is provided on the gate insulating layer  24  extends to the data line (not shown). Consequently, the semiconductor pattern  32  has substantially the same shape as that of the conventional data pad portion. Further, the data pad portion has data pads  28  that are filled at the holes associated with the semiconductor pattern  32  and is also overlapped with the inner circumference of each semiconductor pattern  32 . Each data pad  28  is in contact with the gate insulating layer  24  around the hole defined by the semiconductor pattern  32  having the substantially ring shaped configuration. Then, an organic protective layer is disposed on the entire surface of the gate insulating layer  24  that is provided with the semiconductor pattern  32  and the data pads  28 . The organic protective layer is patterned so that it is eliminated from the data pad portion. 
     The gate insulating layer  24  is also patterned by the etching process. When the gate insulating layer  24  is etched, the semiconductor pattern  32  functions as an etching prevention member to prevent the undercutting of the gate insulating layer  24 . Consequently, the gate insulating layer  24  remains only under the data pads  28  and the semiconductor patterns  32 . Note that if the width of the semiconductor pattern  32  is too narrow, the gate insulating layer  24  will be undercut. If this occurs, the data pad can be damaged by the TAB process, and the transparent electrode that is to be formed after the etching process may become opened due to a step that is caused by the semiconductor pattern  32  and the undercut gate insulating layer  24 . Thus, the width of the semiconductor pattern  32  must be set appropriately to prevent undercutting of the gate insulating layer  24 . Finally, the transparent electrodes  20  are formed on the semiconductor patterns  32  and the data pads  28 . The transparent electrodes  20  protect the data pads  28 . The data pad portion with the above-described structure eliminates the need for an organic protective layer and the gate insulating layer  24  that is around the data pads  28 , and partially exposes the surface of the lower glass substrate  22 , as shown in FIG.  9 B. 
     Accordingly, the data pad portion prevents separation of the transparent electrode  20  due to the weak adhesive force between the organic protective layer and the gate insulating layer  24  when the TAB process is repeated. Also, an ACF (not shown) to bind the TCP to the data pad portion is in contact directly with the surface of the lower glass substrate  22 . As a result, the adhesion between the data pad portion and the TCP remains strong. 
     As described above, preferred embodiments of the present invention eliminate the need for the organic protective layer and the gate insulating layer that is conventionally positioned around the pads. Accordingly, preferred embodiments of the present invention prevent separation of the transparent electrode when the TAB process is repeated. Further, preferred embodiments of the present invention allow for an ACF to bind the TCP to the pad portion and to directly contact the surface of the lower glass substrate  22 . As a result, the adhesion between the pad portion and the TCP remains strong. Further, preferred embodiments of the present invention provide a semiconductor pattern around the pad area for preventing the undercutting of the gate insulating layer so that the pads are are not damaged and the transparent electrodes are not opened. 
     While the invention has been particularly shown and descibed with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and oher changes in form and details may be made therein without departing from the spirit and scope of the invention.