Abstract:
A liquid crystal display according to the present invention uses an organic layer treated with H 2  plasma before fabricating an inorganic layer on the top of the organic layer. When forming thin film transistors (TFT) used in the LCD, an Indium Tin Oxide layer is fabricated above the TFTs and acts as a pixel electrode. When the organic layer, such as a passivation layer, is treated with the H 2  plasma, an intermediate layer having an O—H bonding structure is formed to enhance bonding or attachment of an inorganic layer, such as an ITO layer, to the organic layer.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a substrate of a liquid crystal display device (LCD), and a method for manufacturing the same. In particular, the present invention relates to a method for manufacturing a substrate of a liquid crystal display wherein an organic layer and a pixel electrode thereon are firmly cohering to each other.  
           [0003]    2. Description of Related Art  
           [0004]    A conventional substrate of a liquid crystal display device having a switching element and a pixel electrode is formed, mentioned as follows, referring to FIGS. 1 a  and  1   b.  FIGS. 1 a  and  1   b  show the inverse staggered structure of the thin film transistor (TFT).  
           [0005]    Referring to FIG. 1 a,  a gate electrode  60   a  is formed on a transparent substrate  10 . A gate insulation layer  50  is deposited thereon to cover the gate electrode  60 . A semiconductor layer  90  with an island shape is formed on the gate insulation layer  50  on the gate electrode  60 . On the surface of the semiconductor layer  90 , ohmic contact layers  92   a  and  92   b  are formed in separate regions. On one ohmic contact layer  92   a,  a source electrode  70   a  is formed and a data line  70  connecting to the source electrode  70   a  is formed on the gate insulation layer  50 . On the other ohmic contact layer  92   b,  a drain electrode  70   b  is formed. As the gate electrode, source electrode and the drain electrode are formed, a TFT acting as a switching element is completed.  
           [0006]    On the substrate having the TFT, an organic layer  55 , including a benzocyclobutene (or BCB) generally containing combinations of C, H and O elements, is formed. A contact hole  30  is formed to expose some surface of the drain electrode  70   b  by patterning the organic layer  55 . The reason for using the organic layer on the substrate of the LCD is that after being coated on the substrate of which surface has stepped profile, the surface of the organic layer does not project the stepped profile. That is, a substantially flat surface of the organic layer is formed. Also, the organic layer has a lower coefficient constant similar to the inorganic layer, such as silicon oxide (SiO x ) or silicon nitride (SiN x ). Therefore, after the organic layer is formed on the substrate, a pixel electrode can be formed over the area on which the data line is formed in order to maximize the aperture ratio. In that regard, an ITO (Indium Tin Oxide) layer is deposited on the organic layer having the contact hole  30  and is patterned to form a pixel electrode  40  by etching the ITO layer with the photo-resist  88  pattern using a wet etching method. It is possible to overlap the pixel electrode and some portion of the data line because problems such as cross talk do not occur between them due to the characteristics of the organic material mentioned above.  
           [0007]    However, during the etching process, the ITO layer can be easily peeled off from the organic layer or a vacancy can occur between the ITO layer and the organic layer because the coherency between them is very weak. As a result, the etchant can penetrate into the vacancy so that the pixel electrode can be over etched, as shown in FIG. 1 b.  FIG. 1 b  shows the undesirable patterned results which (A) is the peeled off portion of the pixel electrode (B) and (C) are the over etched portion of the pixel electrode.  
           [0008]    If the edge portions of the ITO layer, which constitutes the pixel electrode, are over etched by the etchant, then the size of the pixel electrode is reduced and becomes irregular. This is referred to as a CD loss. As a result, the aperture ratio becomes smaller than the expected value.  
         SUMMARY OF THE INVENTION  
         [0009]    In order to overcome the above-mentioned problem, an object of the present invention is to suggest a method for manufacturing a substrate of the LCD in which the coherence between the pixel electrode and the organic layer is enhanced as well as the structure of the LCD by the same method. Another object is to protect the pixel electrode from being over etched by enhancing the coherence of the pixel electrode with the organic layer.  
           [0010]    Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0011]    The present invention suggests a method in which an intermediate thin layer  156  is formed by treating the surface of the organic layer  155  with plasma of H 2 , as shown in FIG. 2 a.  The organic layer typically comprises C, H, and O radicals. As a result, the surface of the organic layer has an unstable state. The present invention suggests an enhanced method for making the surface of the organic passivation layer more stable by treating it with plasma containing H element. Consequently, the pixel electrode fabricated on the treated region has stronger adherence and maintains its shape and size. When the surface of the organic layer is treated with the H 2  plasma, the surface has an O—H bonding structure. Therefore, as an ITO layer or a metal layer is deposited thereon, the coherence of it on the organic layer is enhanced. As a result, it is possible to protect the inorganic layer, such as an ITO layer or an metal layer deposited on the organic layer, from being peeling off and being undesirably patterned.  
           [0012]    According to this scope, the present invention suggests an LCD comprising a substrate, a TFT on the substrate, an organic layer covering the TFT, an intermediate-layer  180 , as shown in FIG. 2 b  is formed by treating the surface of the organic layer with H 2  plasma, a contact hole exposing a surface of a drain electrode of the TFT by removing some portion of the organic layer and the intermediate layer, a pixel electrode connecting to the drain electrode through the contact hole. The present invention also suggests an LCD according to the above-mentioned structure wherein the intermediate layer is further formed on the side wall of the contact hole.  
           [0013]    Additionally, the present invention suggests a method for manufacturing an LCD comprising steps of forming a TFT on a substrate, forming an organic layer covering the TFT, treating the surface of the organic layer with H 2  plasma, forming a contact hole exposing some surface of the drain electrode by removing some of the organic layer and intermediate layer, forming a pixel electrode connecting to the drain electrode through the contact hole. The present invention also suggests a method for manufacturing an LCD according to the above-mentioned method wherein the step of forming a contact hole is performed after forming the organic layer, and then the step of treating the surface of the organic layer is performed so that the side wall of the contact hole also has the intermediate layer on the surface.  
           [0014]    These and other aspects, features and advantages of the present invention will be better understood by studying the detailed description in conjunction with the drawings and the accompanying claims.  
       
    
    
     BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS  
       [0015]    A detailed description of embodiments of the invention will be made with reference to the accompanying drawings, wherein like numerals designate corresponding parts in the several figures.  
         [0016]    [0016]FIGS. 1 a  and  1   b  are cross-sectional views illustrating the conventional substrate of a liquid crystal display;  
         [0017]    [0017]FIGS. 2 a  and  2   b  are cross-sectional views showing the present invention; and  
         [0018]    [0018]FIGS. 3 a - 3   d ,  4   a - 4   c ,  5  and  6  are cross-sectional views illustrating the substrate of a liquid crystal display according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    Referring to the figures and preferred embodiments, we will explain about the present invention in detail. Referring to the FIGS. 3 a - 3   d , the first preferred embodiment is explained as follows.  
         [0020]    As described above, a gate electrode  160  is formed on a transparent substrate  110 . A gate insulation layer  150  is deposited thereon to cover the gate electrode  160 . A semiconductor layer  190  with an island shape is formed on the gate insulation layer  150  on the gate electrode  160 . On the surface of the semiconductor layer  190 , ohmic contact layers  192   a  and  192   b  are formed in separate regions. On one ohmic contact layer  192   a,  a source electrode  170   a  is formed and a data line  170  connecting to the source electrode  170   a  is formed on the gate insulation layer  150 . On the other ohmic contact layer  192   b,  a drain electrode  170   b  is formed. As the gate electrode, source electrode and the drain electrode are formed, a TFT acting as a switching element is completed.  
         [0021]    An organic layer  155  including one of BCB, Fluorinated polyimide, Teflon, Cytop and Acrylic Resin is formed on the substrate layers having the TFT preferably by a spin coating method. Alternatively, any other methods known to one of ordinary skill in the art may be used to apply the organic layer  155  to the substrate. Then, the surface of the organic layer  155  is treated with H 2  plasma so that an intermediate layer  156  having an O—H bonding structure is formed, as shown in FIG. 3 a.    
         [0022]    After a photo resist  188  is coated on the whole surface having the intermediate layer  156  in the O—H bonding structure, the photo resist  188  is developed in a certain pattern to form a contact hole  130  exposing some surface of the drain electrode  170   b.  Then the intermediate layer  156  and the organic layer  155  covering the exposed portion of the drain electrode are removed preferably by a dry etching method to form a contact hole  130 , as shown in FIG. 3 b.    
         [0023]    After all of the photo resist  188  is removed, an ITO layer  140  is deposited on the whole surface of the substrate preferably by a sputtering method. Then, another layer photo resist  188  is coated thereon. After the photo resist  188  is developed in a certain pattern, the ITO layer  140  is patterned preferably by a wet etching method, as shown in FIG. 3 c.  According to this embodiment, the coherence of the organic layer  155  and the ITO layer  140  is enhanced because the intermediate layer  156  enhances the adhesion between them. Therefore, the etchant cannot penetrate into regions represented as (A), (B) and (C) in FIG. 3 c.    
         [0024]    Thereafter, a pixel electrode  140 , the ITO layer formed on the intermediate layer  156  in O—H bonding structure, is patterned without being peeled off or over etched.  
         [0025]    Referring to FIGS. 4 a - 4   c , the second embodiment of the present invention is explained as follows. As the gate electrode, source electrode and the drain electrode are formed on a substrate  110 , a TFT acting as a switching element is completed, as mentioned in the first preferred embodiment. An organic layer  155  including one of BCB, Fluorinated polyimide, Teflon™, Cytop and Acrylic Resin all containing oxygen element is formed on the substrate having the TFT preferably by a spin coating method. And the organic layer  155  covering the exposed portion of the drain electrode is removed preferably by a dry etching method to form a contact hole  130 . Then, the surface of the organic layer  155  is treated with H 2  plasma so that an intermediate layer  156  having O—H bonding structure is formed.  
         [0026]    According to the second embodiment, the side wall of the contact hole  130  is also coated with the intermediate layer  156  having the O—H bonding structure, as shown in FIG. 4 a.  The exposed drain electrode  170   b  is not damaged by the etchant at all because the drain electrode  170   b  is made of metal such as aluminum or chromium.  
         [0027]    An ITO layer  140  is deposited on the whole surface of the substrate preferably by a sputtering method. Then, another photo resist  188  is coated thereon. After the photo resist is developed in a certain pattern, the ITO layer  140  is preferably patterned by a wet etching method, as shown in FIG. 4 b.    
         [0028]    After the etching step is finished, all of the photo resist is removed and the substrate of the LCD is completed. According to this embodiment, the coherence of the organic layer  155  and the ITO layer  140  is enhanced because the intermediate layer  156  enhances the adhesion between them.  
         [0029]    Referring to FIG. 5, the third embodiment of the present invention comprises a step of forming an oxide intermediate layer  156 ′ by treating the organic layer  155  with O 2  plasma before forming the intermediate layer  156  using H 2  plasma treatment as described in the first embodiment.  
         [0030]    Treated with O 2  plasma, the surface of the organic layer  155  is changed into a silicon oxide (SiO x ) layer referred herein as the oxide intermediate layer  156 ′, so that the surface becomes stable. However, the oxide intermediate layer  156 ′ may still contain some unstable regions. After being treated again with H 2  plasma, the surface of the silicon oxide layer is changed into an intermediate layer  156  having an O—-H bonding structure.  
         [0031]    In the third embodiment, the method for manufacturing the LCD is similar to the first embodiment, except that one of the differences is the step of treating the organic layer  155  with O 2  plasma before treating with H 2  plasma.  
         [0032]    Referring to FIG. 6, the fourth embodiment of the present invention comprises a step of forming an oxide intermediate layer  156 ′ by treating the organic layer  155  with O 2  plasma before forming the intermediate layer  156  using H 2  plasma treatment as described in connection with the second embodiment.  
         [0033]    A contact hole  130  is formed just after the organic layer  155  is formed. Treated with O 2  plasma, the surface of the organic layer  155  is changed into a silicon oxide (SiO 2 ) layer, the oxide intermediate layer  156 ′. After being treated again with H 2  plasma, the surface of the silicon oxide layer is changed into an intermediate layer  156 ′ having an O—H bonding structure.  
         [0034]    According to the fourth embodiment, the side wall of the contact hole  130  also has the oxide intermediate layer  156 ′ including the silicon oxide layer and the intermediate layer  156 ′ in an O—H bonding structure.  
         [0035]    In the third and fourth embodiments, it is preferable to replace the O 2  plasma with Ar plasma. Also, the H 2  plasma treatment may be performed before treating the surface with the O 2  plasma or Ar plasma.  
         [0036]    The present invention suggests a method for manufacturing the LCD panel comprising a step of treating the organic layer with H 2  plasma for enhancing the coherence force with an inorganic layer such as an ITO layer thereon. Treated with H 2  plasma, the surface of the organic layer transforms into an intermediate layer having an O—H bonding structure.  
         [0037]    The intermediate layer coheres with the inorganic layer such as an ITO, silicon nitride (SiNx) or silicon oxide (SiOx), or the metal layer such as Al, Cr, Mo, W or Ta, very well.  
         [0038]    Therefore, according to the scope of the present invention, it is possible to prevent an inorganic layer from being peeled off or over etched by a penetrating etchant.  
         [0039]    While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.  
         [0040]    The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.