Abstract:
A method of manufacturing a liquid crystal display holding a liquid crystal layer between a picture element substrate on which a pixel electrode driven by a thin film transistor is formed and a opposed counter substrate and forming a terminal to an external driving circuit on the picture element substrate, includes forming a semiconductor layer on the substrate, forming a gate insulating film on the semiconductor layer, forming a gate electrode on the gate insulating film, forming a source-drain region in the semiconductor layer, forming a source-drain wire on the substrate, forming a terminal wire on the substrate, forming insulating inorganic films on regions of the terminal wire on the external driving circuit and a display area sides, forming an organic resin film on the insulating inorganic film, and forming a conductive film on the terminal wire. The conductive film has a predetermined distance to the organic resin film.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a liquid crystal display provided with a terminal to be connected to an external driving circuit, and a method of manufacturing the same. 
   2. Description of the Related Art 
   The liquid crystal display is formed so that an insulating substrate provided thereon with a thin film transistor, a pixel electrode, a wire, a terminal to be connected to an external driving circuit, and the like, and an insulating substrate provided thereon with a color filter, a counter electrode and the like are disposed in an opposed state with a liquid crystal held therebetween. 
   The wire is formed out of a metal, such as Al, Cr, Mo and the like. The terminal to be connected to an external driving circuit is formed so that an electrode surface formed out of Cr and Mo is covered with a transparent conductive oxide film, such as an indium tin oxide (ITO) film and an indium zinc oxide (IZO) film. 
   To connect the external driving circuit and terminal together, anisotropic conductive particles are used. (See, e.g., JP-A-2000-155335 (page 6, FIG. 2).) 
   In the above-described liquid crystal display, the surface of the terminal to be connected to an external driving circuit is exposed, and in an atmospheric moisture-exposed state. Since the terminal surface is made of a conductive oxide film, the surface is rarely oxidized anymore in the atmospheric air, so that the connecting of the terminal to an external driving circuit can be done stably. However, since ITO and IZO are oxides, they are very active, and readily turn into cathodes in an oxidation-reduction reaction. For example, when the humidity is high with the water in the atmospheric air deposited on the surface of the terminal, a cell reaction is liable to occur between the terminal and Cr or Mo electrode which constitutes a lower layer electrode of ITO and IZO. 
   SUMMARY OF THE INVENTION 
   The present invention has been made with a view to solving the above-mentioned problems, and provides a liquid crystal display capable of reducing the occurrence of the breaking of wire (electrolytic corrosion) which is ascribed to a cell reaction of a terminal to be connected to an external driving circuit, and having a terminal structure excellent in contact characteristics of a terminal portion, and a manufacturing method therefor. 
   According to an aspect of the present invention, a method of manufacturing a liquid crystal display, which holds a liquid crystal layer between a picture element substrate on which a pixel electrode driven by a thin film transistor is formed and a counter substrate opposed to the picture element substrate, and which forms a terminal to be connected to an external driving circuit on at least one side of the picture element substrate, the method including forming a semiconductor layer on the substrate, forming a gate insulating film on the semiconductor layer, forming a gate electrode on the gate insulating film, forming a source-drain region by an ion-injecting impurity into the semiconductor layer, forming a source-drain wire on the substrate, forming a terminal wire on the substrate, forming insulating inorganic films on a region of the terminal wire on a side of the external driving circuit and on a region thereof on a side of a display area, forming an organic resin film on the insulating inorganic film, and forming a conductive film on the terminal wire including at least a part of the insulating inorganic film. Preferably, the conductive film has a predetermined distance to the organic resin film. 
   According to the present invention, an end portion on the side of a display panel of the terminal of the substrate and an end portion on the side of an external driving circuit of the terminal thereof are covered with an insulating protective film. The portion not covered with the protective film of an upper surface of the terminal has a transparent conductive film so that an exposed area of the terminal is reduced to a minimum level, the terminal being thereby rendered difficult to be exposed to the atmospheric air. This enables the terminal to be rendered difficult to receive the influence of the contamination of impurities, etc. It also becomes possible to hold down the occurrence of a cell reaction due to the water contained in the atmospheric air. Since the transparent conductive film on the terminal is not in contact with the organic resin film of a high hygroscopicity constituting a protective film, the occurrence of a cell reaction due to the water contained in the organic resin film can also be held down. Therefore, imperfect electric contact of the terminal portion due to electrolytic corrosion thereof, and the breaking of wire in the terminal portion can be reduced. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a top view showing the terminal structure in the liquid crystal display in the first embodiment of the present invention; 
       FIG. 2  is a sectional view showing the terminal structure in the liquid crystal display in the first embodiment of the present invention; 
       FIGS. 3A to 3C  are schematic diagrams showing a flow of the manufacturing of the liquid crystal display in the first embodiment of the present invention; 
       FIG. 4  is a sectional view showing the terminal structure in the liquid crystal display in the second embodiment of the present invention; 
       FIG. 5  is a top view showing the terminal structure in the liquid crystal display in the third embodiment of the present invention; 
       FIG. 6  is a sectional view showing the terminal structure in the liquid crystal display in the third embodiment of the present invention; and 
       FIGS. 7A to 7C  are schematic diagrams showing a flow of the manufacturing of the liquid crystal display in the third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   First Embodiment 
     FIG. 1  is a top view of a liquid crystal display of the first embodiment according to the present invention.  FIG. 2  is a sectional view taken along the broken line A-B in  FIG. 1 , and a sectional view of a region in a display area. Referring to the explanatory drawing used for each embodiment which will be described below, the same reference numerals and letters are added to the same or corresponding portions to omit the description thereof. 
   Referring to  FIGS. 1 and 2 , the liquid crystal display in this embodiment has a picture element transistor  203  formed on a glass substrate  201 , a pixel electrode  205  driven by the picture element transistor  203 , a signal wire  109 , an interlayer insulating film  207 , a protective film  209  made of an insulating inorganic film  105  and an organic resin film  107 , and a terminal  101  for being connected to an external driving circuit. The terminal  101  is made of the signal wire  109  in which Cr/Al/Cr films are laminated and a transparent conductive film  103  made of an ITO film. 
   A flow of the manufacturing of the liquid crystal display in the mode of this embodiment will be described. Referring to  FIG. 3A , a silicon layer is formed on the glass substrate  201  to form a gate insulating film  211 . A gate electrode is then formed, and a source-drain region thereafter to form the picture element transistor  203 . After the picture element transistor  203  is formed, the interlayer insulating film  207  is laminated thereon. 
   Referring to  FIG. 3B , first openings  213   a ,  213   b  are formed in the interlayer film  207  and gate insulating film  211  on the source-drain region of the picture element transistor  203 , and then source-drain wires  215  on the source-drain region. Simultaneously with the formation of the source-drain wires  215 , a signal wire  109  on the side of the external driving circuit. The source-drain wires  215  and signal wire  109  constitute a laminated structure of Cr/Al/Cr. 
   Referring to  FIG. 3C , the insulating inorganic film  105  is formed on the interlayer insulating film  207  including the source-drain wire  215  and signal wire  109 . The organic resin layer  107  is formed on the insulating inorganic film  105  to form the protective film  209 . In the protective film  209 , second to fourth openings  217   a ,  217   b ,  217   c  are made by a photoengraving process, and an Al film is then formed to obtain a reflector  303  made of an Al film  301  on a surface of the second opening  217   a . An ITO film is then formed, and thereafter a transmission electrode  305  made of an ITO film on a surface of the third opening  217   b  by a photoengraving process to obtain a pixel electrode  205 . On a surface of the fourth opening  217   c , a transparent conductive film  103  made of an ITO film is formed on a surface of the fourth opening  217   c  to obtain the terminal  101 . Both end portions of the terminal  101 , i.e. the end portions on the side of a display area and on the side of the external driving circuit are covered with the protective film  209  formed by laminating the organic resin film  107  on the insulating inorganic film  105 . The organic resin film  107  on the insulating inorganic film  105  is in a retreated state with respect to an end portion thereof. This structure can be obtained by dry etching the insulating inorganic film  105  with the patterned organic resin film  107  used as a mask, and then exposing the resultant product to an oxygen atmosphere plasma, or also by carrying out a photoengraving process two times. Thus, in the terminal  101 , a region in which the fourth opening  217   c  is formed in the insulating inorganic film  105  on the signal wire  109  and its circumferential insulating inorganic film  105  are covered with the ITO film constituting the transparent conductive film  103 , and the ITO film is not in contact with the organic resin film  107  on the insulating inorganic film  105 . A distance between the portions of the insulating inorganic film  105  which cover the signal wire  109  is set in this embodiment to 200 μm. This distance may be set to a required minimum level for obtaining an electrical contact with the external driving circuit, and not necessarily set to 200 μm. 
   The insulating inorganic film  105  and organic resin film  107  which form the protective film  209  are made of a silicon nitride film constituting a passivation film used in the manufacturing of the display area and an acrylic organic resin film used for forming the irregular surface of the reflecting plate or for improving the numerical aperture. Therefore, a new step may not be added, and the productivity is not lowered. The signal wire  109  constituting the terminal  101  is made of the film in the layer identical with that of the source-drain wire  215  of the picture element transistor  203  formed in the display area. Therefore, a new step may not be added, and the productivity is not lowered. 
   According to the present invention in the first embodiment described above, the signal wire  109  constituting the terminal  101  is not exposed to the atmospheric air, and the ITO film on the signal wire  109  prevents the terminal from contacting the acrylic organic resin film  107  of a high hygroscopicity, so that it is difficult to receive the influence of contamination of impurities, etc. It is also possible to hold down the occurrence of an electrolytic corrosion reaction ascribed to the water contained in the atmospheric air and acrylic organic resin film  107 . This enables the occurrence of imperfect contact of the terminal due to electrolytic corrosion, and the breaking of wire in the terminal to be lowered. 
   Second Embodiment 
   In the first embodiment, the ITO film formed in the step identical with that in which the source-drain wire  215  is formed, via the fourth opening  217   c  made in the insulating inorganic film  105 , and formed on the signal wire  109  made of laminated films or Cr/Al/Cr which is made of a layer identical with that of the source-drain wire  215 , is provided so that the ITO film does not contact the organic resin film  107 . On the other hand, a Cr film is formed on the lower side of the ITO film of the terminal  101  in this embodiment. 
     FIG. 4  is a sectional view of the liquid crystal display in the second embodiment. 
   Referring to  FIG. 4 , a flow of the manufacturing of the liquid crystal display in this embodiment will be described. Second to fourth openings  217   a ,  217   b ,  217   c  are formed in the same manner as in the first embodiment in a protective layer  209  on an interlayer insulating film  207  including a source-drain wire  215  and a signal wire  109 , by a photo engraving process. A laminated Al/Cr film is then formed, and thereafter an Al film of a reflector  303 , which constitutes a pixel electrode  205 , by a photoengraving process. The Cr film in a region of a transmission electrode  305  which forms the pixel electrode  205  by the photoengraving process is then removed, and a transparent conductive film made of ITO film is thereafter formed. An ITO film of the transmission electrode  305 , and a laminate of an ITO film and a Cr film  405  of a terminal  101  are then formed. Thus, the reflector  303  made of a laminate of a Cr film  401  and an Al film  403  is formed on a surface of the second opening  217   a , and the transmission film  305  made of an ITO film on an upper surface of the fourth opening  217   b , to form the pixel electrode  205 . An electrode made of an ITO film and a Cr film  405  and constituting the transparent conductive film  103  is formed on a surface of the fourth opening  217   c , to obtain a terminal  101 . Both ends, i.e. a display area side end and an external driving circuit side end of the terminal  101  are covered with a protective film  209  formed by laminating an organic resin film  107  on an insulating inorganic film  105 . The organic resin film  107  on the insulating inorganic film  105  is in a retreated state with respect to an end portion of the insulating inorganic film  105  in the same manner as in the first embodiment. Thus, in the terminal  101 , a region in which the fourth opening  217   c  is formed in the insulating inorganic film  105  on the signal wire  109 , and the portion of the insulating inorganic film  105  which surrounds this region are covered with the ITO film constituting the transparent conductive film  103 , and the ITO film is formed so that the ITO film does not contact the organic resin film  107  on the insulating inorganic film  105 . 
   Even in the second embodiment, the insulating inorganic film  105  and organic resin film  107  which form the protective film  209  for obtaining the protective film  209  in the same manner as in the first embodiment are made of the same silicon nitride film, i.e. the same passivation film as was used for the manufacturing of the display area, or the same acrylic organic resin film as was used for forming an irregular surface of the reflecting plate or improving the numerical aperture thereof. Therefore, a new step may not be added, and the productivity is not lowered. Moreover, since the signal wire  109  forming the terminal  101  is made of a film in the layer identical with that of the source-drain wire  213  for the picture element transistor  203  formed in the display area, a new step may not be added, and the productivity is not lowered. 
   According to the invention in the second embodiment described above, the signal wire  109  constituting the terminal  101  is not exposed to the atmospheric air, and the ITO film on the signal wire  109  avoids contacting the acrylic organic resin film  107  of a high hygroscopicity. Therefore, this embodiment rarely receives the influence of the contamination of impurities, etc. It is also possible to hold down the occurrence of an electrolytic corrosion reaction ascribed to the water contained in the atmospheric air and the water contained in the acrylic organic resin film  107 . Therefore, the imperfect electric contact of the terminal portion due to the electrolytic corrosion and, moreover, the breaking of wire in the terminal portion can be minimized. The ITO film constituting the terminal  101  is formed via the Cr film  405  in a lower layer, and a distance between the ITO film and the Al used for the signal wire  109  can be set large, so that the corrosion resistance of the ITO film is improved. 
   Third embodiment 
   In the first and second embodiments, the ITO film was formed on the source-drain wire  215  via the fourth opening  217   c  formed in the insulating inorganic film  105 , in the step identical with that for forming the source-drain wire  215 , on the Cr/Al/Cr wire so as not to contact the organic resin film  107 , on the Cr/Al/Cr wire, which was a film of the layer identical with the source-drain wire  215 . On the other hand, the mode of this embodiment is formed so that a signal from an external driving circuit is inputted into a display panel by utilizing a Cr electrode wire formed in the same layer as a gate wire. 
     FIG. 5  is a top view of the liquid crystal panel of the second embodiment according to the present invention.  FIG. 6  is a sectional view taken along the broken line A-B in  FIG. 5  and a sectional view of a region in the display area. 
   Referring to  FIGS. 5 and 6 , a Cr/Al/Cr wire  501  made of the layer identical with that of a source-drain wire  215  of a picture element transistor formed on a display area and an ITO film constituting a transparent conductive film  103  covering the wire  501  in a terminal  101  to be connected to the external driving circuit are formed so that the wire  501  and ITO film  103  do not contact an insulating inorganic film  105  and an organic resin film  107 . Namely, in the terminal  101 , a terminal wire  501  made of a laminate of Cr/Al/Cr films formed of a layer identical with that of the source-drain wire  215  is brought into electrical contact with a Cr electrode wire, which constitutes a lower layer  505  made of a layer identical with that of a gate electrode  503 , via a fifth opening  507  formed in an interlayer insulating film  207 . A signal from the external driving circuit is thus inputted into a display panel by utilizing the wire  505  formed in a lower layer. 
   A flow of the manufacturing of the liquid crystal display of this embodiment will be described. Referring to  FIG. 7A , a picture element transistor  203  is formed on a glass substrate  201 . During this time, a lower layer wire  505  is formed simultaneously with the formation of a gate electrode  503  of a picture element transistor made of a Cr film. After the picture element transistor  203  and lower layer wire  505  are formed, an interlayer insulating film  207  is laminated on the latter. 
   Referring to  FIG. 7B , a first opening  213  is formed in the interlayer film  207  in a source-drain region of the picture element transistor  203  and gate insulating film  211 , and a fifth opening  507  in the interlayer insulating film  207  on the lower layer wire  505  of the terminal  101 . After the first opening  213  and fifth opening  507  are made, a source-drain wire  215  is formed so that the source-drain wire  215  communicates with the source-drain region of the picture element transistor. Simultaneously with the formation of the source-drain wire  215 , a terminal wire  501  is formed so that the terminal wire  501  communicates with the lower layer wire  505  of the external driving circuit side terminal  101 . Each of the source-drain wire  215  and terminal wire  501  is made of a laminated structure of Cr/Al/Cr films. 
   Referring to  FIG. 7C , an insulating inorganic film  105  is formed in such a region of the interlayer insulating film  207  including the source-drain wire  215  that excludes the portion to become the terminal  101 . The organic resin film  107  is formed on the insulating inorganic film  105 , to turn the same into a protective film  209 . A second opening  217   a  and a third opening  217   b  are formed in the protective film  209  by the photoengraving process. An electrode made of an Al/Cr film is formed in the second opening  217   a , and a transmission electrode made of ITO on the surface of the third opening  217   b  to turn the same electrode into a pixel electrode  205 . A transparent conductive film  103  made of ITO is formed on the terminal wire  501  in the region which is to become the terminal  101 , to obtain the terminal  101 . The display area side of the terminal  101  is covered with the protective film  209  formed by laminating the organic resin film  107  on the insulating inorganic film  105 . The organic resin film  107  on the insulating inorganic film  105  is in a retreated state with respect to an end portion of the insulating inorganic film  105 . This structure can be obtained by dry etching the insulating inorganic film  105  with a patterned organic resin film  107  used as an etching mask, and thereafter exposing the resultant product to oxygen atmospheric plasma. This structure can also be obtained even by conducting a photoengraving process two times. In the terminal  101 , the terminal wire  501  is thus covered with the ITO film constituting the transparent conductive film  103 , and the ITO film does not contact the insulating inorganic film  105  and organic resin film  107  on the insulating inorganic film  105 . 
   According to the invention in the third embodiment described above, the area of the exposed portion of the terminal electrode is held down to a minimum level, and the ITO film on the signal wire avoids contacting the acrylic organic resin film  107  of a high hygroscopicity and inorganic insulating film  105 , so that the signal wire is rarely exposed to the atmospheric air and rarely receives the influence of contamination of impurities. Moreover, this enables the occurrence of electrolytic corrosion ascribed to the water contained in the atmospheric air and the water contained in the acrylic organic resin film to be held down. Therefore, the imperfect electrical contact of the terminal portion ascribed to the electrolytic corrosion, and the breaking of wire of the terminal portion can be reduced. In addition, the protective film on the side of the external driving circuit is omitted, and the corrosion resistance with respect to the water is further increased. Since the wire formed in the lower layer is utilized, the area to be used for wiring can be increased.