Abstract:
This invention relates to an organic electro-luminescence device and a method of fabricating the same that is capable of reducing an inverse taper of a bus electrode. An organic electro-luminescence display device comprises: an anode electrode including a transparent electrode and a bus electrode; a cathode electrode crossing the anode electrode; and an organic layer located at a cross both the anode electrode and the cathode electrode, wherein the bus electrode has an inclination angle of 30° to 70°.

Description:
[0001]     This application claims the benefit of Korean Patent Application No. P2004-19684 filed in Korea on Mar. 23, 2004, which is hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to an electro-luminescence display device, and more particularly, to an organic electro-luminescence display device and a method of fabricating the same that is capable of reducing an inverse taper of a bus electrode.  
         [0004]     2. Description of the Related Art  
         [0005]     Recently, there have been developed various flat panel display devices reduced in weight and bulk that is capable of eliminating disadvantages of a cathode ray tube (CRT). Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED) device, a plasma display panel (PDP) and an electro-luminescence (EL) display device, etc. device. Especially, the EL display device has characteristics of a wide viewing angle, a high aperture rate and a high color purity, etc., such that it can be highlighted into a post-generation display device.  
         [0006]     Such the EL display device comprises an anode electrode and a cathode electrode  12  with an organic layer therebetween, wherein the organic layer includes a hole carrier layer, a light-emitting layer, and an electron carrier layer. Electrons and holes emitted from these anode electrode and cathode electrode are re-combined with each other, thereby generating a visible light. At this time, the generated visible light is emitted, via the anode electrode, into an exterior to thereby display a predetermined picture or image.  
         [0007]     Meanwhile, as shown in  FIG. 1 , an anode electrode  52  includes: a transparent  56  formed on a substrate  51 ; and a bus electrode  54  formed on one side of the transparent electrode  56  to compensate a resistance component of the transparent electrode  56 .  
         [0008]     Herein, the bus electrode  54  is formed by etching a chrome Cr, a molybdenum Mo, and a copper Cu, etc. using an etchant consisted of phosphoric acid in a rage of 60 to 65 weight %, nitric acid in a range of 5 to 6 weight %, acetic acid of 10 weight %, and water in a range of 19 to 25 weight %. An inclination angle of the bus electrode 54 formed by using the etchant is relatively large as about 80° to 110°. Accordingly, a taper of the bus electrode  54  is deteriorated. In other words, the bus electrode  54  is formed in an inverse taper type in which the lower portion thereof has a narrower width than the upper portion thereof. An insulating film  58  formed to cover the anode electrode  52  having the bus electrode  54  makes a step coverage to be deteriorated, so that a pinhole A exposing the bus electrode  54  is occurred as shown in  FIG. 2 . An insulation breakdown is occurred by the pinhole, so that there is a problem that a reliance of the electro-luminescence display device is deteriorated, e.g., the anode electrode  52  and a cathode electrode are shorted.  
       SUMMARY OF THE INVENTION  
       [0009]     Accordingly, it is an object of the present invention to provide an organic electro-luminescence display device and a method of fabricating the same that is capable of reducing an inverse taper of a bus electrode.  
         [0010]     In order to achieve these and other objects of the invention, an organic electro-luminescence display device comprises: an anode electrode including a transparent electrode and a bus electrode; a cathode electrode crossing the anode electrode; and an organic layer located at a cross both the anode electrode and the cathode electrode, wherein the bus electrode has an inclination angle of 30° to 70°.  
         [0011]     The bus electrode has an inclination angle of 30° to 50°.  
         [0012]     The anode electrode includes: the transparent electrode; and the bus electrode located on the transparent electrode.  
         [0013]     The anode electrode includes: the bus electrode; and the transparent electrode located on the bus electrode.  
         [0014]     In order to achieve these and other objects of the invention, a method of fabricating an organic electro-luminescence display device comprises: forming an anode electrode including a transparent electrode and a bus electrode on a substrate; forming an organic layer generating light on the substrate having the anode electrode; and forming a cathode electrode crossing the anode electrode on the substrate having the organic layer, wherein the bus electrode has an inclination angle of 30° to 70°.  
         [0015]     The bus electrode has an inclination angle of 30° to 50°.  
         [0016]     The forming the anode electrode having the transparent electrode and the bus electrode on the substrate includes: forming the transparent electrode on the substrate; and forming the bus electrode having the inclination angle of 30° to 70° on the transparent electrode.  
         [0017]     The forming the anode electrode having the transparent electrode and the bus electrode on the substrate includes: forming the bus electrode having the inclination angle of 30° to 70° on the substrate; and forming the transparent electrode so as to contact with the bus electrode on the substrate having the bus electrode.  
         [0018]     The forming the bus electrode having the inclination angle of 30° to 70° includes: depositing a metal on the substrate; and patterning the metal by a photolithography process and an etching process using an etchant to form the bus electrode.  
         [0019]     The etchant is consisted of phosphoric acid in a range of 55 to 60 weight %, nitric acid in a range of 10 to 12 weight %, acetic acid in a range of 8 to 10 weight %, and water in a range of 18 to 27 weight %.  
         [0020]     The etchant has a temperature of a normal temperature to 45° C.  
         [0021]     The etchant has a temperature of 30° C. to 35° C.  
         [0022]     The metal includes at least one of chrome, molybdenum, and cupper. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     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:  
         [0024]      FIG. 1  is a perspective view illustrating an anode electrode of a related art organic electro-luminescence display device;  
         [0025]      FIG. 2  is a sectional view illustrating a pinhole phenomenon of an insulating film by a bus electrode shown in  FIG. 1 ;  
         [0026]      FIG. 3  is a plan view illustrating an organic electro-luminescence display device according to the present invention;  
         [0027]      FIG. 4  is a sectional view illustrating the organic electro-luminescence display device taken along a line II-II′ in  FIG. 3 ;  
         [0028]      FIG. 5  is a sectional view illustrating the organic electro-luminescence display device taken along a line III-III′ in  FIG. 3 ;  
         [0029]      FIGS. 6A  to  6 F are plan views and sectional views representing a method of manufacturing the organic electro-luminescence display device according to the present invention; and  
         [0030]      FIGS. 7A and 7B  are sectional views illustrating a taper angle of a bus electrode in accordance with a temperature of an etchant. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.  
         [0032]     Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to FIGS.  3  to  7 B.  
         [0033]      FIG. 3  is a plan view illustrating an organic electro-luminescence display device according to the present invention, and  FIG. 4  is a sectional view illustrating the organic electro-luminescence display device taken along a line II-II′ in  FIG. 3 .  
         [0034]     Referring to  FIGS. 3 and 4 , the related art electro-luminescence display device includes an insulating film  6 , a barrier rib  8 , and an organic layer  10  formed between, an anode electrode  4  and a cathode electrode  10 , which are insulated from each other and crossing each other on a substrate  2 .  
         [0035]     A plurality of anode electrodes  4  is provided on the substrate  2  in such a manner to be spaced at a predetermined distance from each other. A first driving signal is supplied to such the anode electrode  4  in order to emit an electron(or hole).  
         [0036]     As shown in  FIG. 5 , the anode electrode  4  includes: a transparent electrode  4   a  made of a transparent conductive material, e.g., indium-tin-oxide ITO, etc., on a substrate  2 ; and a bus electrode  4   b  made of chrome Cr, molybdenum Mo, copper Cu, and etc. on one side of the transparent electrode  4   a  to compensate a resistance component of the transparent electrode  4   a . Furthermore, the anode electrode  4  may include: a bus electrode  4   b  formed on a substrate  2 ; and a transparent electrode  4   a  formed on the substrate  2  having the bus electrode 4 b.    
         [0037]     Herein, the bus electrode  4   b i s formed to have a relatively smooth inclination angle of about 30° to 70°. Preferably, the bus electrode  4   b  is formed to have the inclination angle of about 30° to 50° 
         [0038]     The insulating film  6  is formed in a lattice type so as to expose an aperture for each EL cell area on the substrate  2  having the anode electrode  4 .  
         [0039]     The barrier rib  8  is formed in a direction crossing the anode electrode  4 , and is formed in parallel to the cathode electrode  12  by a predetermined distance to partition adjacent EL cells. In other words, the barrier rib  8  separates the organic layers  10  from each other and the cathode electrodes  12  from each other between the adjacent EL cells. Further, the barrier rib  8  has an overhang structure in which the upper portion thereof has a larger width than the lower portion thereof.  
         [0040]     The organic layer  10  is made of an organic compound on the insulating film  6 . In other words, the organic layer  10  is formed by depositing a hole carrier layer, a light-emitting layer and an electron carrier layer onto the insulating film  6 .  
         [0041]     A plurality of cathode electrodes  12  is provided on the organic layer  10  in such a manner to be spaced at a predetermined distance from each other, and in such a manner to be crossed with the anode electrodes  4 . A second driving signal is supplied to the cathode electrode  12  in order to emit a hole( or electron).  
         [0042]     As set forth above, in the organic electro-luminescence display device according to the present, the bus electrode  4   b  is formed to have an inclination angle of 30° to 70°. Accordingly, a taper of the bus electrode  4   b  having a relatively smooth inclination angle becomes improved, so that a step coverage of the insulating film  6  formed to cover the bus electrode  4   b  becomes improved. Thus, it is possible to prevent an insulation breakdown.  
         [0043]      FIGS. 6A  to  6 F are plan views and sectional views representing a method of manufacturing the organic electro-luminescence display device according to the present invention.  
         [0044]     Firstly, a transparent conductive material, e.g., indium-tin-oxide, etc., is deposited and then patterned on a substrate  2 , to thereby form a transparent electrode  4   a  of an anode electrode on the substrate as shown in  FIG. 6 .  
         [0045]     Chrome Cr or Molybdenum Mo, etc. is deposited on the substrate  2  having the transparent electrode  4   a  and then is patterned by a photolithography process and an etching process using an etchant consisted of phosphoric acid in a range of 55 to 60 weight %, nitric acid in a range of 10 to 12 weight %, acetic acid in a range of 8 to 10 weight %, and water in a range of 18 to 27 weight %, to thereby form a bus electrode  4   b  of an anode electrode having a taper angle of 30° to 70° as shown in  FIG. 6B . The etching process of the bus electrode  4   b  will be described in detail later.  
         [0046]     A photosensitive insulating material is deposited and then patterned on the substrate  2  having the anode electrode  4 , to thereby form a insulating film  6  as shown in  FIG. 6C . The insulating film  6  is formed in a lattice type at an entire portion except for a light-emitting portion.  
         [0047]     A photosensitive insulating material is deposited and then patterned on the substrate  2  having the insulating film  6 , to thereby form a barrier rib  8  as shown in  FIG. 6D . The barrier rib  8  is formed with a predetermined distance from adjacent barrier ribs in a direction crossing the anode electrode  4 , and is formed at a non-light emitting portion.  
         [0048]     An organic layer  10  is formed on the substrate having the barrier rib  8  as shown in  FIG. 6E . The organic layer  10  includes hole carrier layer, a light emitting layer, and an electron carrier layer.  
         [0049]     A cathode electrode  12  is formed on the substrate  2  having the organic layer  10  as shown in  FIG. 6F . At this time, the cathode electrode  12  is entirely deposited to be formed, but is separated for each EL cell by the barrier rib having a relatively high height to be formed.  
         [0050]     Meanwhile, the bus electrode  4   b  of the anode electrode according to the present invention is formed with result that a metal such as chrome Cr, molybdenum Mo, copper Cu, etc. is etched by an anisotropic etching manner using an etchant consisted of compositions shown in table 1, at a temperature of a normal temperature to 45° C., preferably temperature of about 30° C. to 35° C. The bus electrode  4   b  formed by the etching manner using the etchant has an inclination angle of 30° to 70°.  
                                                         TABLE 1                                   Phosphoric   Nitric   Acetic               acid   acid   acid   Water                                    Composition   55 to 60   10 to 12   8 to 10   18 to 28       content (wight %)                  
 
         [0051]     As shown in Table 1, a content of nitric acid becomes larger by about double amount than that of the related art, so that an etching speed of a metal making the bus electrode  4   b  becomes slower. Accordingly, the bus electrode  4   b  can be formed with an inclination angle smaller than that of the related art.  
         [0052]     Meanwhile, an etching amount and inclination angle of the bus electrode  4   b  formed by the etchant shown in Table 1 are differentiated depending upon a temperature of the etchant as shown in Table 2.  
                               TABLE 2                                       Inclination       Temperature of   first   second   third   angle of bus       etchant (° C.)   location   location   location   electrode                   30° C.   0.20 μm   0.21 μm   0.28 μm   40° C. to 49° C.       40° C.   0.54 μm   0.44 μm   0.52 μm   54° C. to 63° C.                  
 
         [0053]     In a case that a temperature of the etchant is 40° C., the bus electrode  4   b  located at a first location(near upper corner of right side in the substrate) is etched by about 0.54 μm from end of a photo-resist pattern  30  formed by an etching process and a developing process as shown in  FIG. 7A , the bus electrode  4   b  located at a second location(near center of the substrate) is etched by about 0.44 μm from end of the photo-resist pattern  30 , and the bus electrode  4   b  located at a third location(near lower corner of left side of the substrate) is etched by about 0.5,2 μm from end of the photo-resist pattern  30 . As set forth above, when the temperature of the etchant is 40° C., the bus electrode  4   b  is over-etched by a first width d 1  from end of the photo-resist pattern  30  and the bus electrode  4   b  has a inclination angle α of about 54° to 63°.  
         [0054]     On the other hand, in a case that a temperature of the etchant is 30° C., the bus electrode  4   b  located at a first location(near upper corner of right side in the substrate) is etched by about 0.20 μm from end of a photo-resist pattern  30  formed by an etching process and a developing process as shown in  FIG. 7B , the bus electrode  4   b  located at a second location(near center of the substrate) is etched by about 0.21 μm from end of the photo-resist pattern  30 , and the bus electrode  4   b  located at a third location(near lower corner of left side of the substrate) is etched by about 0.28 μm from end of the photo-resist pattern  30 . As set forth above, when the temperature of the etchant is 30° C., the bus electrode  4   b  is over-etched by a second width shorter than the first width d 1 , from end of the photo-resist pattern  30 , and the bus electrode  4   b  has a inclination angle β of about 40° to 49°.  
         [0055]     As set forth above, when the temperature of the etchant is 30° C. as compared with 40° C., an over-etched amount of the bus electrode  4   b  is a relatively small and inclination angle of the bus electrode  4   b  becomes relatively smaller.  
         [0056]     As described above, in the organic electro-luminescence display device and the method of fabricating the same according to the present invention, the bus electrode is formed to have the inclination angle of 30° to 70°. Accordingly, the taper of the bus electrode having a relatively smooth inclination angle becomes improved, so that a step coverage of the insulating film formed to cover the bus electrode becomes improved. Thus, it is possible to prevent an insulation breakdown.  
         [0057]     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.