Abstract:
A method of fabricating a liquid crystal display device that is adapted to improve yield. In the method, a gate electrode, a gate pad and a gate insulating film are formed over a substrate. A semiconductor layer, source and drain electrodes, and a data pad are formed over the gate insulating film. Inorganic and organic insulating materials are deposited onto the gate insulating film. The organic insulating material is removed from a partial area on the drain electrode, the gate pad the data pad, and the organic insulating material is exposed and developed to leave a portion of the organic insulating material at a peripheral portion of the gate and data pads. The gate insulating film, and inorganic and organic insulating materials are patterned to leave the organic insulating material at an area other than a partial area, thereby providing an inorganic protective film and an organic protective film.

Description:
[0001]    The present application claims, under 35 U.S.C § 119, the benefit of Korean Patent Application No. P2001-081774 filed Dec. 20, 2001, which is herein fully incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention pertains to a liquid crystal display, and more particularly to a method of fabricating a liquid crystal display device that has improved yield.  
           [0004]    2. Description of the Related Art  
           [0005]    Generally, a liquid crystal display (LCD) controls the light transmissivity of liquid crystal cells arranged in a matrix pattern in response to a video signal to thereby display a picture corresponding to the video signals on a liquid crystal display panel. To this end, the LCD includes a liquid crystal display panel having liquid crystal cells arranged in an active matrix, and driving integrated circuits (IC&#39;s) drive the liquid crystal cells.  
           [0006]    The driving IC&#39;s are usually manufactured in chip form. The driving IC&#39;s are mounted on a tape carrier package (TCP) film attached to the outer periphery of the liquid crystal panel. The driving IC&#39;s are connected by a tape automated bonding (TAB) system while being mounted along the edge of the liquid crystal panel, when they are connected by a chips on glass (COG) system. In the TAB system, the driving IC&#39;s are electrically connected to a pad portion provided at the liquid crystal panel by means of the TCP.  
           [0007]    [0007]FIG. 1 is a plan view showing a structure of a conventional LCD device.  
           [0008]    In FIG. 1, the LCD device has a lower plate  4  and an upper plate  6  that oppositely adhere to each other. The LCD device includes a picture display part  2  having liquid crystal cells arranged in a matrix pattern, and gate pad portions GP and data pad portions DP connected between the driving IC&#39;s and the picture display part  2 .  
           [0009]    In the picture display part  2 , data lines supplied with data signals and gate lines supplied with gate signals are arranged at the lower plate  4  so as to cross each other. Each of the crossing parts is provided with a thin film transistor for switching the liquid crystal cell, and a pixel electrode connected to the thin film transistor drives the liquid crystal cell. The upper plate  6  includes coated color filters, and the color filters are separated for each cell area by black, matrices. A common transparent electrode is coated on the surfaces of the color filters. Upper and lower plates  6  and  4  are spaced from each other by a spacer to provide a cell gap, which is filled with a liquid crystal material. The upper and lower plates  6  and  4  adhere to each other by means of a sealant coated on a seal  10  at the outside of the picture display part  2 .  
           [0010]    The edge area of the lower plate  4  that does not overlap with the upper plate  6  is provided with gate pad portions GP and data pad portions DP. The gate pad portion GP applies a gate signal from the gate driving IC to the gate line of the picture display part  2 . The data pad portion DP applies a video signal from the data driving IC to the data line of the picture display part  2 .  
           [0011]    In the LCD device having the structure described above, a protective film for protecting the metal electrode and the thin film transistors entirely coats the lower plate  4 . The pixel electrode is formed on the protective film for each cell area. The protective film is an organic protective film that enhances the aperture ratio of the pixel.  
           [0012]    As shown in FIG. 2, a gate pad  14  of the gate pad portion GP along with a gate line of the picture display part  2  is provided on a lower substrate  1 . A gate insulating film  22  and an organic protective film  24  are sequentially entirely coated on the lower substrate  1  to cover the gate pad  14 . A gate contact hole  16 a forms by patterning the gate insulating film  22  and the organic protective film  24  to expose a portion of the gate pad  14 . A gate protective electrode  20  is formed on the organic protective film  24  to electrically connect the gate pad  14  to the gate protective electrode  20  via the gate contact hole  16 a.  
           [0013]    As shown in FIG. 3, a data pad  18  of the data pad part DP along with a data line of the picture display part  2  are provided on the gate insulating film  22 . The organic protective film  24  entirely coats the gate insulating film  22  to cover the data pad  18 . A data contact hole  16   b  forms by patterning the organic protective film  24  to expose a portion of the data pad  18 . A data protective electrode  26  formed on the organic protective film  24  is electrically connected, via the data contact hole  16   b,  to the data pad  18 .  
           [0014]    The gate pad portion GP and the data pad portion DP are in contact with the TCP mounted with the driving IC by the TAB system. The gate pad  14  and the data pad  18  are electrically connected to the TCP via the gate protective electrode  20  and the data protective electrode  26  provided on the organic protective film  24 . This has the goal of preventing damage to the gate pad  14  and the data pad  18  upon repetition of the TCP adhering process required for the TAB system. Also, the gate pad  14  and the data pad  18  are not exposed and hence do not react with peripheral moisture to cause their oxidative corrosion.  
           [0015]    In order to electrically connect the TCP to the gate protective electrode  20  and the data protective electrode  26 , an anisotropic conductive film  12  as shown in FIG. 4A and FIG. 4B is provided. The anisotropic conductive film  12  is coated with conductive particles  28 , which form a current path between the TCP, the gate protective electrode  20  and the data protective electrode  26 .  
           [0016]    If the data pad portion DP and the gate pad portion GP adhere to the TCP mounted with the driving IC by the TAB system, then it is necessary to repeat the process of adhesive bonding and separating the TCP many times when defects caused by a misalignment occur. Accordingly, as the organic protective film  24  has a weak adhesion characteristic with respect to the gate insulating film  22 , it is removed along with the TCP in the process of separating the TCP. In this case, there is a problem in that unevenness of the surface removed with the organic protective film  24  causes a weak adhesion characteristic upon re-adhering the TCP.  
           [0017]    Furthermore, if the organic protective film  24  on the gate pad  14  and the data pad  18  is removed, then the gate protective electrode  20  and the data protective electrode  26  thereon also are removed. Accordingly, there is a problem in that the gate pad  14  and the data pad  18  are exposed to be damaged or oxidized, thereby deteriorating the characteristics of the gate pad  14  and the data pad  18 .  
           [0018]    Moreover, if a mask for eliminating the residual organic protective film  24  is used for a smooth repair process, then the productivity is reduced and hence a production time is prolonged.  
         SUMMARY OF THE INVENTION  
         [0019]    Accordingly, it is an object of the invention to provide a method of fabricating a liquid crystal display device that is adapted to improve the yield and overcome problems and disadvantages of the related art.  
           [0020]    A method of fabricating a liquid crystal display device according to an embodiment of the present invention, includes forming a gate electrode and a gate pad over a substrate, forming a gate insulating film over the substrate, forming a semiconductor layer over the gate insulating film, forming a source electrode, a drain electrode and a data pad over the gate insulating film, depositing an inorganic insulating material over the gate insulating film, depositing an organic insulating material over the inorganic insulating material, removing selectively the organic insulating material at a partial area over the drain electrode, the gate pad and the data pad to leave a portion of the organic insulating material over the gate pad and the data pad, patterning the inorganic insulating material using at least a portion of the remaining organic insulating material as a mask, thereby providing an organic protective film and a part of an inorganic protective film over the source and drain electrodes and a part of the inorganic protective film over the gate and data pads, and forming a transparent electrode pattern over the inorganic protective film and the organic protective film.  
           [0021]    A method of fabricating a liquid crystal display device according to an embodiment of the present invention, includes forming a gate electrode and a gate pad over a substrate, forming a gate insulating film over the substrate, forming a semiconductor layer over the gate insulating film, forming a source electrode, a drain electrode and a data pad over the gate insulating film, depositing an inorganic insulating material on the gate insulating film, depositing an organic insulating material over the inorganic insulating material, removing selectively the organic insulating material at a partial area over the drain electrode, the gate pad and the data pad, to leave a portion of the organic insulating material over the gate pad and the data pad, patterning the gate insulating film and the inorganic insulating material using at least a portion of the remaining(organic insulating material as a mask, thereby providing an inorganic protective film, an organic protective film, a drain contact hole, a gate contact hole and a data contact hole, and forming a pixel electrode on the inorganic protective film by depositing a transparent conductive film onto the inorganic protective film and the organic protective film and patterning the transparent conductive film, and forming a gate protective electrode and a data protective electrode on the inorganic protective film.  
           [0022]    A method for forming a display device according to an embodiment of the present invention, includes forming a thin film transistor (TFT), a gate pad and a data pad on a substrate, depositing sequentially an inorganic insulating material and an organic insulating material on the substrate having the TFT, the gate pad and the data pad, selectively removing the organic insulating material using a diffracting mask to form a patterned organic insulating layer, selectively removing the inorganic insulating material, using at least a portion of the patterned organic insulating layer as a mask to define contact holes for the TFT, the gate pad and the data pad, and forming electrodes in the contact holes.  
           [0023]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    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:  
         [0025]    [0025]FIG. 1 is a schematic plan view showing a structure of a conventional liquid crystal display device;  
         [0026]    [0026]FIG. 2 is a section view of the gate pad portion shown in FIG. 1;  
         [0027]    [0027]FIG. 3 is a section view of the data pad portion shown in FIG. 1;  
         [0028]    [0028]FIG. 4A and FIG. 4B illustrate anisotropic conductive, films provided on the gate pad portion and the data pad portion shown in FIG. 2 and FIG. 3, respectively;  
         [0029]    [0029]FIG. 5 is a plan view showing a structure of a liquid crystal display device according to an embodiment of the present invention;  
         [0030]    [0030]FIG. 6 is a section view of the liquid crystal display device taken along the A-A′, B-B′ and C-C′ lines in FIG. 5;  
         [0031]    [0031]FIG. 7 illustrates examples of masks positioned at the upper portions of the gate pad portion and the data pad portion shown in FIG. 6; and  
         [0032]    [0032]FIG. 8A to FIG. 8G are section views showing a method of fabricating the liquid crystal display device shown in FIG. 6 according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0033]    Advantages of the present invention will become more apparent from the detailed description given herein after. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.  
         [0034]    [0034]FIG. 5 and FIG. 6 show a liquid crystal display (LCD) device according to an embodiment of the present invention.  
         [0035]    As shown, the LCD device includes a picture display part TP having liquid crystal cells arranged in a matrix pattern. Gate pad portions GP and data pad portions DP are connected between driving IC&#39;s, (not shown) and the picture display part TP.  
         [0036]    The picture display part TP has data lines  34  supplied with data signals, and gate lines,  32  supplied with gate signals are arranged at a lower plate (not shown) to cross each other. Each of the crossing parts is provided with a thin film transistor (TFT) for switching the liquid crystal cell and having a gate electrode  36 , a source electrode  38  and a drain electrode  40 . An inorganic protective film  48  protects the TFT, and an organic protective film  62  enhances the aperture ratio. A pixel electrode  52  in electrical contact with the drain electrode through a drain contact hole  50   b  is provided on the organic protective film  62  for each cell area.  
         [0037]    The gate pad portion GP is connected to a gate driving IC (not shown) positioned at one end of the gate line  32 . The gate pad portion GP applies a gate signal for controlling the TET from the gate driving IC to the gate line  32  of the picture display part TP. The gate pad portion GP includes a gate pad  54  connected to the gate line  32 , and a gate protective electrode  5 s connected to the gate driving IC. The gate insulating film  42  and the inorganic protective film  48  are provided between the gate pad  54  and the gate protective electrode  58 .  
         [0038]    The data pad portion DP is connected to a data driving IC (not shown) positioned at one end of the data line  34 . The data pad portion DP applies a data signal for controlling the TFT from the data driving IC to the data line  34  of the picture display part TP. The data pad portion DP includes a data pad  56  connected to the data line  34 , a data protective electrode  60  connected to the data driving IC, and the inorganic protective film  48  provided between the data pad,  56  and the data protective electrode  60 .  
         [0039]    [0039]FIG. 7 shows a grating  64  having one or more diffraction parts and a transmission part that are positioned at the gate pad portion GP and the data pad portion DP of the LCD device. This grating  64  is used in a mask which is used to pattern the layers of the LCD device. To accomplish this, the transmission part of the grating  64  is positioned to correspond with an area provided with a gate contact hole  50   a  over the gate pad  54  and a data contact hole  50   c  over the data pad  56 . The diffraction part of the grating  64  has a relatively small width and is positioned to correspond with an area other than the gate contact hole  50   a  and the data contact hole  50   c.  Thus, since the gate pad portion GP and the data pad portion are not provided with the organic protective film  62 , the inorganic protective film  48  protects the gate pad portion GP and the data pad portion DP. The TFT of the picture display part TP is protected by the inorganic protective film  48  and the organic protective film  62  for enhancing an aperture ratio.  
         [0040]    The organic protective film  62  corresponding to the data pad portion DP and the gate pad portion GP of the LCD device is entirely removed to prevent removal of the gate protective electrode  58  and the data protective electrode  60  caused by a weak adhesion characteristic of the organic protective film  62  upon repetition of the TAB process Further, an anisotropic conductive film for adhering the gate pad portion GP and the data pad portion DP to the TCP is in direct contact with the inorganic protective film  48  to enhance an adhesive force of the TAB.  
         [0041]    [0041]FIG. 8A to FIG. 8G show a method of fabricating the LCD device shown in FIG. 6 using a diffraction mask having a grating according to an embodiment of the present invention.  
         [0042]    In FIG. 8A, a gate metal layer is deposited on the substrate  31  by a deposition technique such as sputtering. In one embodiment, the gate metal layer is made from at least one of aluminum(Al), copper(Cu), etc. Then, the gate metal layer is patterned by the photolithography including an etching process to provide the gate pad  54  and the gate electrode  36  on the substrate  31 .  
         [0043]    In FIG. 8B, the gate insulating film  42  is formed on the substrate  31  provided with the gate pad  54  and the gate electrode  36 . The gate insulating film  42  is made from an inorganic insulating material such as silicon oxide (SiO x ), silicon nitride (SiN x ), or silicon oxynitride (SiOxNy). First and second semiconductor layers are continuously deposited on the gate insulating film  42  by a chemical vapor deposition (CVD) technique or other suitable technique. The first semiconductor layer is formed from undoped amorphous silicon. The second semiconductor layer is formed from amorphous silicon doped with an n-type or p-type impurity such as boron, phosphorous, arsenic, etc. Then, the first and second semiconductor layers are patterned by the photolithography including a dry etching process, e.g., plasma etch, to provide an active layer  44  and an ohmic contact layer  46 .  
         [0044]    In FIG. 8C, a data metal layer is deposited on the gate insulating film  42  provided with the active layer  44  and the ohmic contact layer  46  by a CVD technique, sputtering or any other suitable technique.  
         [0045]    The data metal layer is made from, e.g., chromium (Cr), molybdenum (Mo), etc. Then, the data metal layer is patterned by photolithography including a wet etching process to provide the data pad  56 , the source electrode  38  and the drain electrode  40 . Subsequently, the ohmic contact layer  46  exposed between the source electrode  38  and the drain electrode  40  is removed by a dry etching process or any other suitable process to separate the source electrode  38  and the drain electrode  40 . A portion of the ohmic contact layer  40  is removed, and hence a portion corresponding to the gate electrode  36  between the source and drain electrodes  38  and  40  at the active layer  44  makes a channel.  
         [0046]    In FIG. 8D, an inorganic insulating layer  48   a  is formed on the gate insulating film,  42  of the substrate  31  provided with the data pad  56 , the source electrode  38  and the drain electrode  40 . The inorganic insulating layer  48   a  is made from an inorganic material, preferably from silicon nitride (SiN x )  
         [0047]    An organic insulating layer  62   a  is formed on the substrate  31  provided with the inorganic insulating layer  48   a.    
         [0048]    The organic insulating layer  62   a  is made from an organic insulatingmaterial such as an acrylic or methacrylic organic compound, isoprene compound, phenol-formaldehyde resin, benzocyclobutene (BCB) or PFCB (perfluorocyclobutane). In one embodiment, the organic insulating layer  62   a  is made preferably from acrylic photoresist. The acrylic photoresist can be a negative resist material and can be chemically enhanced.  
         [0049]    An example in which acrylic photoresist is used as the organic insulating layer  62   a  will be described below.  
         [0050]    A diffracting mask  66  is positioned at the upper portion of the substrate  31  provided with the acrylic photoresist  62   a.  The diffracting mask  66  has a grating  64  forming a diffraction part  66   a  and a transmission part  66   b,  and a shielding part  66   c.  The transmission part  66   b  of the diffraction mask  66  is positioned at an area where a gate contact hole, a data contact hole and a drain contact hole is to be made later. The diffraction part  66   a  is positioned at an area of the gate pad portion GP and the data pad portion DP excluding the gate contact hole and the data contact hole. The shielding part  66   c  is positioned at the other area.  
         [0051]    In FIG. 8E, the diffracting mask  66  positioned at the upper portion of the substrate  31  is used to expose and develop the acrylic photoresist  62   a.  The acrylic photoresist  62   a  is removed from an area corresponding to the transmission part  66   b  of the diffracting mask  66  by an exposure and development process, thereby exposing portions of the inorganic insulating layer  48   a.  The acrylic photoresist  62   a  equal to about 10% to 50% of its initial thickness is left at an area corresponding to the diffraction part  66   a  while the acrylic photoresist  62   a  equal to its initial thickness is left at an area corresponding to the, shielding part  66   c.    
         [0052]    In FIG. 8F, according to an embodiment of the present invention, the remaining acrylic photoresist  62   a  is used as a mask to remove portions of the inorganic insulating layer  48   a  so as to form contact holes  50   b  and  50   c,  and to remove portions of the inorganic insulating layer  48   a  and the gate insulating film  42  so as to form a contact hole  50   a.  Thereafter, a certain thickness of the acrylic photoresist  62   a  is removed, which results in the organic protective film  62  over the TFT region, but not over the gate and data pads  54  and  56 . This process produces the inorganic protective film  48 , the organic protective film  62 , the gate contact hole  50   a,  the drain contact hole  50   b  and the data contact hole  50   c  formed on the substrate  31 . Thus, the inorganic protective film  48  is provided at an area other than the gate contact hole  50   a,  the drain contact hole  50   b  and the data contact hole  50   c,  and this area excludes the transmission part  66   b  of the diffracting mask  66 . The organic protective film  62  is formed on the TFT of the picture display part TP, which is an area corresponding to the shielding part  66   c  of the diffracting mask  66 . The gate contact hole  50   a,  the drain contact hole  50   b  and the data contact hole  50   c  are formed at an area corresponding to the transmission part  66   b  of the diffracting mask  66 .  
         [0053]    In accordance with another embodiment, instead of completely removing the organic protective film  62  over the gate and data pads  54  and  56  after the contact holes  50   a,    50   b  and  50   c  are defined, the present invention performs these two steps simultaneously. That is, while the portions of the patterned organic protective film  62  over the gate and data pads  54  and  56  and TFT are being removed (or etched away from the top to bottom), the remaining portions of the patterned organic protective film  62  over the gate and data pads  54  and  56  and TFT are used as a mask to form the contact holes  50   a,    50   b  and  50   c.  An ashing technique, a dry etching, and/or other known suitable technique may be used in these processes.  
         [0054]    In FIG. 8G, a transparent electrode layer is formed on the organic protective film  62  and the inorganic protective film  48  by a deposition technique such as sputtering. The transparent electrode layer is made from indium-tin-oxide (ITO), indium-zinc-oxide (IZO) or indium-tin-zinc-oxide (ITZO), etc. Then, The transparent electrode layer is patterned by photolithography, including an etching process to provide the pixel electrode  52 , the gate protective electrode  58  and the data protective electrode  60 . The pixel electrode  52  is electrically connected to the drain electrode  40  via the drain contact hole  50   b,  which passes through the organic protective film  62  and the inorganic protective film  48 . The gate protective electrode  58  electrically connects to the gate pad  54  via the gate contact hole  50   a,  which passes through the gate insulating film  42  and the inorganic protective film  48 . The data protective electrode  60  electrically connects to the data pad  56  via the data contact hole  50   c,  which passes through the inorganic protective film  48 .  
         [0055]    As described above, according to an embodiment of the invention, the organic protective film of the pad portion is removed by the diffraction and exposure. Accordingly, a removal of the transparent electrode layer caused by a weak adhesion characteristic of the organic protective film upon repetition of the TAB process can be prevented. Hence a damage and an oxidization of the pad portion caused by the removal of the transparent electrode layer can be prevented.  
         [0056]    Also, the anisotropic conductive film is in direct contact with the inorganic insulating layer by the entire removal of the organic protective film of the pad portion, so that the adhesive force of the TAB can be enhanced. Furthermore, a repair-effectiveness of the tape carrier package is improved to enhance the yield and productivity.  
         [0057]    It is to be understood that the foregoing descriptions and specific embodiments shown herein are merely illustrative of the best mode of the invention and the principles thereof, and that modifications and additions may be easily made by those skilled in the art without departing for the spirit and scope of the invention, which is therefore understood to be limited only by the scope of the appended claims.