Abstract:
A method of fabricating an organic electroluminescent device (OELD) according to the present invention has steps of repairing a pixel region by irradiating a laser on a drain contact hole of a passivation layer in a pixel region in need of the repair; and disabling the connection between an organic electroluminescent diode and a drain electrode of a driving thin film transistor (TFT), where the pixel region of the OELD has i) the driving TFT comprising the drain electrode, ii) the passivation layer covering the driving TFT, while comprising the drain contact hole exposing the drain electrode of the driving TFT, and iii) the organic electroluminescent diode connected to the drain electrode of the driving TFT via the drain contact hole.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of Korean Patent Application No. 10-2010-0090750 filed in Korea on Sep. 15, 2010, which is hereby incorporated by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to an organic electroluminescent device (OELD) and more particularly to a method of fabricating an array substrate for OELD and a method of repairing the same. 
       BACKGROUND OF THE INVENTION 
       [0003]    A cathode ray tube (CRT) has been widely used as a display device. Recently, however, a flat panel display device, such as a plasma display panel (PDP) device, a liquid crystal display (LCD) device and an OELD, is used as a display device instead of the CRT. 
         [0004]    Among these flat panel display devices, the OELD has an advantage in thickness and weight because the OELD does not require a backlight unit. The OELD device is a self-emission type display device. In addition, with comparison to the LCD device, the OELD has many advantages, such as a wide viewing angle, contrast ratio, low power consumption, and past response time. Moreover, since a fabricating method for the OELD is simple, there is another advantage of reducing production costs. 
         [0005]    The OELD is classified into a passive matrix type and an active matrix type. In the active matrix type OELD, a thin film transistor (TFT) as a switching element is disposed at each pixel. Since the active matrix type OELD device has excellent capabilities of high resolution, low power consumption and lifetime with comparison to the passive matrix type OELD, the active matrix type OELD is much widely introduced. 
         [0006]      FIG. 1  is a circuit diagram showing a pixel region of an OELD according to a related art. As shown in  FIG. 1 , a gate line “GL”, a data line “DL”, a power supply line “PL”, a switching thin film transistor (TFT) “STr”, a storage capacitor “StgC”, a driving TFT “DTr”, and an organic electroluminescent diode “E” are formed in one pixel region “P.” The gate line “GL” and the data line “DL” cross each other such that the pixel region “P” is defined, and the power supply line “PL” is formed to be parallel to the data line “DL.” The switching TFT “STr” is formed at crossing portion of the gate and data line “GL” and “DL.” The driving TFT “DTr” is electrically connected to the switching TFT “STr.” 
         [0007]    The driving TFT “DTr” is electrically connected to the organic electroluminescent diode “E.” In more detail, a first electrode of the organic electroluminescent diode “E” is connected to a drain electrode of the driving TFT “DTr,” and a second electrode of the organic electroluminescent diode “E” is connected to the power supply line “PL” (not shown in the figure). The power supply line “PL” provides a source voltage to the organic electroluminescent diode “E.” The storage capacitor “Cst” is disposed between gate and source electrodes of the driving TFT “DTr” (not shown in the figure). 
         [0008]    When a signal is applied to the switching TFT “STr” through the gate line “GL” such that the switching TFT “STr” is turned on, a signal from the data line “DL” is applied to the gate electrode of the driving TFT “DTr,” turning on the driving TFT “DTr.”. As a result, light is emitted from the organic electroluminescent diode “E.” Further, when the driving TFT “DTr” is turned on, a level of an electric current applied from the power supply line “PL” to the organic electroluminescent diode “E” is determined such that the organic electroluminescent diode “E” can produce a gray scale. The storage capacitor “StgC” serves as maintaining the voltage of the gate electrode of the driving TFT “DTr” when the switching TFT “STr” is turned off. Accordingly, even if the switching TFT “STr” is turned off, a level of an electric current applied from the power supply line “PL” to the organic electroluminescent diode “E” is maintained to next frame. 
         [0009]      FIG. 2  is a schematic cross-sectional view of an OELD according to a related art. As shown in  FIG. 2 , the OELD  10  includes a first substrate  1  and a second substrate  2 . The first and second substrates  1  and  2  are spaced apart from each other and attached by a seal pattern  20 . 
         [0010]    On the first substrate  1 , a switching thin film transistor (not shown in the figure), a driving TFT “DTr,” a first electrode  3 , an organic luminescent layer  5  and a second electrode  7  are formed. An absorbing element  13  for absorbing moisture is formed above the second electrode. 
         [0011]    The driving TFT “DTr” is connected to the switching TFT (not shown in the figure), and the first electrode  3  is connected to the driving TFT “DTr.” The organic luminescent layer  5  is disposed on the first electrode  3 , and the second electrode  7  is disposed on the organic luminescent layer  5 . The first and second electrodes  3  and  7 , and the organic luminescent layer  5  interposed between the electrodes constitute an organic electroluminescent diode. 
         [0012]    The organic luminescent layer  5  provides red, green and blue colors. Specifically, first to third organic luminescent patterns  5   a ,  5   b  and  5   c , which respectively emit red, green and blue color lights, are formed in each pixel region. 
         [0013]    When the first electrode  3  is transparent and the second electrode  7  is opaque, light from the organic luminescent layer  5  passes through the first electrode  3  and the first substrate  1 , but not much through the second electrode  7 . This is referred to as a bottom emission type OELD. On the other hand, when the first electrode  3  is opaque and the second electrode  7  is transparent, light from the organic luminescent layer  5  passes through the second electrode  7  and the second substrate  2 , but not much through the first electrode  3 . This is referred to as a top emission type OELD. 
         [0014]    Unfortunately, however, defects are generated in parts of a plurality of pixel regions. For example, some pixels constantly emit light because of an electrical shortage problem in electrical lines resulting from a static electricity or particles. This is referred to as a brightening point defect. 
       SUMMARY OF THE INVENTION 
       [0015]    Accordingly, the present invention is directed to a method of fabricating an array substrate for an OELD and a method of repairing an array substrate for the OELD that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
         [0016]    One object of the present invention is to fabricate or repair an array substrate for an OELD so that a brightening point defect in the OELD is eliminated and the lightening of a pixel is well controlled. 
         [0017]    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. 
         [0018]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method according to one aspect of the present invention comprises steps of repairing a pixel region by irradiating a laser on a drain contact hole of a passivation layer in a pixel region in need of the repair; and disabling the connection between an organic electroluminescent diode and a drain electrode of a driving thin film transistor (TFT), where the pixel region of the OELD has i) the driving TFT comprising the drain electrode, ii) the passivation layer covering the driving TFT, while comprising the drain contact hole exposing the drain electrode of the driving TFT, and iii) the organic electroluminescent diode connected to the drain electrode of the driving TFT via the drain contact hole. 
         [0019]    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 
         [0020]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate some embodiments of the invention and together with the description serve to explain the principles of the invention. 
           [0021]      FIG. 1  is a circuit diagram showing a pixel region of an OELD according to the related art; 
           [0022]      FIG. 2  is a schematic cross-sectional view of an OELD according to the related art; 
           [0023]      FIG. 3  is a schematic cross-sectional view showing one pixel region of an OELD device according to one exemplary embodiment of the present invention; 
           [0024]      FIGS. 4A and 4B  are schematic cross-sectional views showing a repairing process of an OELD according to another exemplary embodiment of the present invention; and 
           [0025]      FIGS. 5A to 5H  are schematic cross-sectional views illustrating a fabricating process of an array substrate for an OELD according to yet another exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Reference will now be made in detail to some embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
         [0027]    The following embodiments and Examples have been included to provide guidance to one of ordinary skill in the art for practicing representative embodiments of the presently disclosed subject matter. In light of the present disclosure and the general level of skill in the art, those of skill can appreciate that the following Examples are intended to be exemplary only and that numerous changes, modifications, and/or alterations can be employed without departing from the scope of the presently disclosed subject matter. 
         [0028]      FIG. 3  is a schematic cross-sectional view showing one pixel region of an OELD device according to one exemplary embodiment of the present invention. 
         [0029]    As shown in  FIG. 3 , an OELD comprises a driving TFT “DTr,” a first electrode  150 , an organic luminescent layer  170  and a second electrode  180  on a substrate  101 . The driving TFT “DTr,” the first electrode  150  and the organic luminescent layer  170  are formed in each pixel region “P,” and the second electrode  180  is formed on a substantially entire of the substrate  101 . The first electrode  150  is connected to the driving TFT “DTr,” and the organic luminescent layer  170  is positioned between the first and second electrodes  150  and  180 . The first electrode  150 , the organic luminescent layer  170  and the second electrode  180  constitute an organic electroluminescent diode. The organic electroluminescent diode is driven by the driving TFT “DTr” to emit light. Although not shown in the figure, a counter substrate can be added above the first substrate  101 . 
         [0030]    In some exemplary embodiments, a switching TFT “STr” is formed on the substrate  101  and in each pixel region “P.” This switching TFT “STr” may control the driving TFT “DTr.” For example, as shown in  FIG. 3  according to one exemplary embodiment of the present invention, the switching TFT “STr” comprises a first gate electrode  102 , a gate insulating layer  110 , a first semiconductor layer  120 , a first source electrode  132  and a first drain electrode  134 . The gate insulating layer  110  is formed on the first gate electrode  102 . The first semiconductor layer  120  is formed on the gate insulating layer  110  and overlaps the first gate electrode  102 . The first semiconductor layer  120  comprises a first active layer  120   a , comprising intrinsic amorphous silicon, and a first ohmic contact layer  120   b , comprising impurity-doped amorphous silicon. In further exemplary embodiments, the first active layer  120   a  may comprise silicon oxide (SiOx) and/or silicon nitride (SiNx). The first source and drain electrodes  132  and  134  are disposed on the first semiconductor layer  120 , and the first drain electrode  134  is spaced apart from the first source electrode  132 . 
         [0031]    In additional exemplary embodiments, the driving TFT “DTr” is connected to and switched by the switching TFT “STr.” As shown in  FIG. 3  according to one exemplary embodiment of the present invention, the driving TFT “DTr” comprises a second gate electrode  104 , a gate insulating layer  110 , a second semiconductor layer  122 , a second source electrode  136  and a second drain electrode  138 . The gate insulating layer  110  is formed on the second gate electrode  104 . The second semiconductor layer  122  is formed on the gate insulating layer  110  and overlaps the second gate electrode  104 . The second semiconductor layer  122  comprises a second active  122   a , comprising intrinsic amorphous silicon, and a second ohmic contact layer  122   b , comprising impurity-doped amorphous silicon. The second source and drain electrodes  136  and  138  are disposed on the second semiconductor layer  122 , and the second drain electrode  138  is spaced apart from the second source electrode  136 . The second gate electrode  104  of the driving TFT “DTr” is connected to the first drain electrode  134  of the switching TFT “STr.” 
         [0032]    Alternately, each of the switching TFT “STr” and the driving TFT “DTr” may be a top gate type TFT where each of the first and second semiconductor layers  120  and  122  comprises poly-crystalline silicon. 
         [0033]    In accordance with one aspect of the present invention, a gate line, a data line, and a power line are formed as follows. Specifically, a gate line (not shown in the figure) is formed on the substrate  101  along a first direction, and a data line  130  is formed on the substrate  101  along a second direction. The gate line and the data line  130  cross each other to define the pixel region “P.” In addition, a power line (not shown in the figure) is formed on the substrate  101  in parallel with one of the gate line and the data line  130  to provide a voltage to the organic electroluminescent diode. 
         [0034]    In accordance with another aspect of the present invention, the gate line is connected to the first gate electrode  102  of the switching TFT “STr,” and the data line  130  is connected to the first source electrode  132  of the switching TFT “STr.” The power line is connected to the second source electrode  136  of the driving TFT “DTr.” 
         [0035]    In accordance with yet another aspect of the present invention, the first electrode  150  of the organic electroluminescent diode is connected to the second drain electrode  138  of the driving TFT “DTr.” Namely, a passivation layer  140 , which covers the driving TFT “DTr” and includes a drain contact hole  142  exposing the second drain electrode  138  of the driving TFT “DTr,” is formed on the driving TFT “DTr”, and the first electrode  150 , which is formed on the passivation layer  140 , contacts the second drain electrode  138  through the drain contact hole  142 . 
         [0036]    In accordance with further aspect of the present invention, the first electrode  150  is formed of a relative high work-function material, and the second electrode  180  is formed of a material having a work-function smaller than the first electrode  150 . For example, the first electrode  150  may be formed of indium-tin-oxide (ITO), and the second electrode  180  may be formed of Ag/Mg or Cu. 
         [0037]    The organic luminescent layer  170  can emit various color lights, such as red, green and blue color lights. For example, first to third organic luminescent patterns, which respective emit red, green and blue color lights, are formed at in each pixel region “P.” The organic luminescent layer  170  emits light by providing voltages to the first and second electrodes  150  and  180 . 
         [0038]    Although not shown in the figure, a bank, which has a lattice shape to surround each pixel region “P,” may be optionally formed on the first electrode  150 . In this case, the organic luminescent layer  170  in each pixel region “P” may be separated by the bank. 
         [0039]    In some exemplary embodiments, the first electrode  150  is transparent and the second electrode  180  is opaque such that light from the organic luminescent layer  170  passes through the first electrode  150  and the substrate  101 , but not much through the second electrode  180 . Thus, this may be referred to as a bottom emission type OELD. 
         [0040]    In the bottom emission type OELD, a brightening point defect may be generated when an electrical shortage is generated in the switching TFT “STr” or the driving TFT “DTr.”For example, the second source electrode  136  and the second drain electrode  138  of the driving TFT “DTR” is electrically shorted by particles or an static electricity, the organic luminescent layer  170  has an on state regardless of a voltage to the second gate electrode  104 . 
         [0041]    Namely, when the switching TFT “STr” is turned on by a voltage to its first gate electrode  102  a voltage of the data line  130  is applied to the second gate electrode  104  of the driving TFT “DTr” through the first source and drain electrodes  132  and  134  of the switching TFT “STr,” turning on the driving TFT “DTr.”. When the driving TFT “DTr” is on, a voltage of the power line (not shown in the figure) is applied to the first electrode  150  of the organic electroluminescent layer through the second source and drain electrodes  136  and  138  of the driving TFT “DTr.” As a result, the organic luminescent layer  170  is turned on and emits light. 
         [0042]    As discussed previously, however, with an electrical shortage between the second source and drain electrodes  136  and  138  of the driving TFT “DTr,” the voltage of the power line (not shown in the figure) is applied to the first electrode  150  of the organic electroluminescent layer through the second source and drain electrodes  136  and  138  of the driving TFT “DTr” even when the driving TFT “DTr” is off. As a result, there is a brightening point defect in the pixel region “P” where the electrical shortage is generated. 
         [0043]    According to some exemplary embodiments of the present invention, the second source electrode  136  may be cut by irradiating a laser beam “LB” to the second source electrode  136  of the driving TFT “DTr” in the pixel region “P,” where the electrical shortage can be generated. As a result, the voltage of the power line can not be applied to the first electrode  150 . 
         [0044]    In further exemplary embodiments, the second source electrode  136  can be cut by irradiating the laser beam “LB” onto the first substrate  101 , which is an image display surface. As a result, the organic luminescent layer  170  does not emit light regardless of a state of the switching TFT “STr” and the driving TFT “DTr.” In other word, there is a darkening point defect in the pixel region “P.” Nonetheless, since the darkening point defect is less sensible than the brightening point defect, production yield of the OELD is increased. 
         [0045]    As described herein, in a bottom emission type OELD, the brightening point defect is overcome by irradiating a laser beam onto an image display surface to cut the second surface electrode of the driving TFT. On the other hand, in a top emission type OELD, it is difficult to irradiate to the second source electrode of the driving TFT because the driving TFT is invisible from the image display surface. Accordingly, after marking a position in the pixel region, where the brightening point defect is generated, the OELD panel can be reversed and a laser beam is irradiated onto a surface opposite to the image display surface to cut the second source electrode of the driving TFT. Unfortunately, however, accuracy may be decreased, and other pixel regions may be irradiated unintentionally. In addition, when the laser beam is irradiated to another unintended line, such as a data line and a gate line, there are problems in all pixel regions connected to the unintentionally irradiated line. 
         [0046]    In some exemplary embodiments, by irradiating a laser beam at a contact portion between the driving TFT and a first electrode, a voltage to the first electrode is prevented such that the brightening point defect is changed into a darkening point defect. 
         [0047]      FIGS. 4A and 4B  are schematic cross-sectional views showing a repairing process of an OELD according to another exemplary embodiment of the present invention. 
         [0048]    As shown in  FIG. 4A , an OELD comprises a driving TFT “DTr,” a first electrode  250 , an organic luminescent layer  270  and a second electrode  280  on a substrate  201 . The driving TFT “DTr,” the first electrode  250  and the organic luminescent layer  270  are formed in each pixel region “P,” and the second electrode  280  is formed on a substantially entire of the substrate  201 . The first electrode  250  is connected to the driving TFT “DTr,” and the organic luminescent layer  270  is positioned between the first and second electrodes  250  and  280 . The first electrode  250 , the organic luminescent layer  270  and the second electrode  280  constitute an organic electroluminescent diode. The organic electroluminescent diode is driven by the driving TFT “DTr” to emit light. Although not shown in the figure, a counter substrate can be added above the first substrate  201 . 
         [0049]    In some exemplary embodiments, a switching TFT “STr” is formed on the substrate  201  and in each pixel region “P.” This switching TFT “STr” may control the driving TFT “DTr.” For example, as shown in  FIG. 4   a  according to one exemplary embodiment of the present invention, the switching TFT “STr” comprises a first gate electrode  202 , a gate insulating layer  210 , a first semiconductor layer  220 , a first source electrode  232  and a first drain electrode  234 . The gate insulating layer  210  is formed on the first gate electrode  202 . The first semiconductor layer  220  is formed on the gate insulating layer  210  and overlaps the first gate electrode  202 . The first semiconductor layer  220  comprises a first active layer  220   a , comprising intrinsic amorphous silicon, and a first ohmic contact layer  220   b , comprising impurity-doped amorphous silicon. In further exemplary embodiments, the first active layer  220   a  may be made of silicon oxide (SiOx) and/or silicon nitride (SiNx). The first source and drain electrodes  232  and  234  are disposed on the first semiconductor layer  220 , and the first drain electrode  234  is spaced apart from the first source electrode  232 . 
         [0050]    In additional exemplary embodiments, the driving TFT “DTr” is connected to and switched by the switching TFT “STr.” As shown in  FIG. 4   a  according to one exemplary embodiment of the present invention, the driving TFT “DTr” comprises a second gate electrode  204 , a gate insulating layer  210 , a second semiconductor layer  222 , a second source electrode  136  and a second drain electrode  138 . The gate insulating layer  210  is formed on the second gate electrode  204 . The second semiconductor layer  222  is formed on the gate insulating layer  210  and overlaps the second gate electrode  204 . The second semiconductor layer  222  comprises a second active  222   a , comprising intrinsic amorphous silicon, and a second ohmic contact layer  222   b , comprising impurity-doped amorphous silicon. The second source and drain electrodes  236  and  238  are disposed on the second semiconductor layer  222 , and the second drain electrode  238  is spaced apart from the second source electrode  236 . The second gate electrode  204  of the driving TFT “DTr” is connected to the first drain electrode  234  of the switching TFT “STr.” 
         [0051]    Alternately, each of the switching TFT “STr” and the driving TFT “DTr” may be a top gate type TFT where each of the first and second semiconductor layers  220  and  222  comprises poly-crystalline silicon. 
         [0052]    In accordance with one exemplary embodiment of the present invention, a gate line, a data line, and a power line are formed as follows. Specifically, a gate line (not shown in the figure) is formed on the substrate  201  along a first direction, and a data line  230  is formed on the substrate  201  along a second direction. The gate line and the data line  230  cross each other to define the pixel region “P.” In addition, a power line (not shown in the figure) is formed on the substrate  201  in parallel with one of the gate line and the data line  230  to provide a voltage to the organic electroluminescent diode. 
         [0053]    In accordance with another aspect of the present invention, the gate line is connected to the first gate electrode  202  of the switching TFT “STr”, and the data line  230  is connected to the first source electrode  232  of the switching TFT “STr.” The power line is connected to the second source electrode  236  of the driving TFT “DTr.” 
         [0054]    In accordance with yet another aspect of the present invention, the first electrode  250  of the organic electroluminescent diode is connected to the second drain electrode  238  of the driving TFT “DTr.” Namely, a passivation layer  240 , which covers the driving TFT “DTr” and includes a drain contact hole  242  exposing the second drain electrode  238  of the driving TFT “DTr,” is formed on the driving TFT “DTr,” and the first electrode  250 , which is formed on the passivation layer  240 , contacts the second drain electrode  238  through the drain contact hole  242 . 
         [0055]    In accordance with further aspect of the present invention, the first electrode  250  is formed of a relative high work-function material, and the second electrode  280  is formed of a material having a work-function smaller than the first electrode  250 . For example, the first electrode  250  may be formed of indium-tin-oxide (ITO), and the second electrode  280  may be formed of Ag/Mg or Cu. 
         [0056]    A passivation layer  240  is disposed on the driving TFT “DTr” and includes a drain contact hole  242  exposing a portion of the second drain electrode  238  of the driving TFT “DTr.” The first electrode  250  is formed on the passivation layer  240  and contacts the portion of the second drain electrode  238  through the drain contact hole  242 . 
         [0057]    The organic luminescent layer  270  can emit various color lights, such as red, green and blue color lights. For example, first to third organic luminescent patterns, which respectively emit red, green and blue color lights, are formed at in each pixel region “P.” The organic luminescent layer  270  emits light by providing voltages to the first and second electrodes  250  and  280 . 
         [0058]    The second electrode  280  may be made thin to be transparent. As a result, light emitted from the organic luminescent layer  270  can pass through the second electrode  280  to display images. This may be referred to as a top emission type OELD. Although not shown in the figure, to increase optical efficiency, a reflective plate may be formed under the first electrode  250 . 
         [0059]    In addition, although not shown in the figure, a bank, which has a lattice shape to surround each pixel region “P,” may be optionally formed on the first electrode  250 . In this case, the organic luminescent layer  270  in each pixel region “P” may be separated by the bank. 
         [0060]    In the top emission type OELD, a brightening point defect may be generated. For example, the second source electrode  236  and the second drain electrode  238  of the driving TFT “DTR” is electrically shorted by particles or an static electricity, the organic luminescent layer  270  is constantly on regardless of a voltage to the second gate electrode  204 . 
         [0061]    Namely, when the switching TFT “STr” is turned on by a voltage to its first gate electrode  202 , a voltage of the data line  230  is applied to the second gate electrode  204  of the driving TFT “DTr” through the first source and drain electrodes  232  and  234  of the switching TFT “STr,” turning on the driving TFT “DTr.” When the driving TFT “DTr” is on, a voltage of the power line (not shown in the figure) is applied to the first electrode  250  of the organic electroluminescent layer through the second source and drain electrodes  236  and  238  of the driving TFT “DTr”. As a result, the organic luminescent layer  270  is turned on and emits light. 
         [0062]    As discussed previously, however, with an electrical shortage between the second source and drain electrodes  236  and  238  of the driving TFT “DTr,” the voltage of the power line (not shown in the figure) is applied to the first electrode  250  of the organic electroluminescent layer through the second source and drain electrodes  236  and  238  of the driving TFT “DTr” even when the driving TFT “DTr” is off. As a result, there is a brightening point defect in the pixel region “P” where the electrical shortage is generated. 
         [0063]    As mentioned above, since the driving TFT “DTr” in the top emission type OELD is invisible from the image display surface, it is difficult to irradiate a laser beam on an image display surface. Accordingly, after marking a pixel region in need of repair, where the brightening point defect is generated, the OELD panel is reversed and a laser beam is irradiated onto a surface opposite to the image display surface to cut the second source electrode of the driving TFT. Unfortunately, however, when a mis-alignment is generated, other pixel regions may be irradiated unintentionally. In this case, a darkening point defect is generated in the other pixel regions. In addition, when the laser beam is irradiated to another unintended line, such as a data line and a gate line, there are problems in all pixel regions connected to the unintentionally irradiated line. 
         [0064]    To prevent these problems, as shown in  FIG. 4B , the brightening point defect is avoided by irradiating a laser beam “LB” to the drain contact hole  242  through the image display surface. The inventors surprisingly found that it is possible to irradiate the laser beam to the drain contact hole on the image display surface because the drain contact hole is visible from the image display surface. Namely, the laser beam “LB” is irradiated onto the second electrode  280  to disable or destroy a connection between the first electrode  250  and the second drain electrode  238 . After the laser beam “LB” is irradiated, the second electrode  280 , the organic luminescent layer  270  and the first electrode  250  are removed such that the second drain electrode  238  is exposed through the drain contact hole  242 . The first electrode is electrically disconnected from the driving TFT “DTr.” As a result, a voltage of the power line (not shown in the figure) is not applied to the first electrode  250  even when the switching TFT “STr” and the driving TFT “DTr” are turned on such that the brightening point defect is changed into a darkening point defect. 
         [0065]    In some exemplary embodiments, the laser beam “LB” is a pulse type and has a wavelength of about 532 nm and energy of about 0.5 to 0.8 mJ. As used herein, the term “about” refers to a range of values ±10% of a specified value. For example, the phrase “about 100 nm” includes ±10% of 100 nm, or from 90 nm to 110 nm. 
         [0066]    The laser beam “LB” according to additional embodiments of the present invention includes, but is not limited to, a laser having a wavelength between about 300 nm and about 700 nm, about 400 nm and about 600 nm, about 500 nm and about 550 nm, and about 520 nm and about 540 nm. By this laser beam “LB,” a connection between the second drain electrode  238  of the driving TFT “DTr” and the first electrode  250  through the drain contact hole  242  is destroyed, and damage to another element is prevented. If the laser beam “LB” is too weak, the connection is incompletely destroyed such that the brightening point defect can not be resolved. On the other hand, if the laser beam is too strong, other elements, for example, the gate line or the data line, is cut such that a darkening point defect is also generated in other pixel regions. 
         [0067]      FIGS. 5A to 5H  are schematic cross-sectional views illustrating a fabricating process of an array substrate for an OELD according to yet another exemplary embodiment of the present invention. 
         [0068]    As shown in  FIG. 5A  according to some embodiments of the present invention, a first metallic material layer (not shown in the figure) is formed on the substrate  201  by depositing a first metallic material and is patterned using various process, including, but not limited to, a mask process to form the first and second gate electrodes  202  and  204 . At the same time, the gate line (not shown in the figure), which is connected to the first gate line  202 , is formed. The first metallic material layer is formed of a relatively low resistance metallic material, including, but not limited to, copper (Cu), Cu alloy, aluminum (Al), Al alloy, and molybdenum (Mo). Next, the gate insulating layer  210  is formed on the first and second gate electrodes  202  and  204 , and the gate line. 
         [0069]    Next, as shown in  FIG. 5B  according to additional embodiments of the present invention, an intrinsic amorphous silicon layer (not shown in the figure) and an impurity-doped amorphous silicon layer (not shown in the figure) are formed on the gate insulating layer  210  by sequentially depositing intrinsic amorphous silicon and impurity-doped amorphous silicon. The intrinsic amorphous silicon and the impurity-doped amorphous silicon layer may be patterned using various methods, including, but not limited to, a mask process to form the first and second active layers  120   a  and  122   a , a first impurity-doped amorphous silicon pattern  224 , and a second impurity-doped amorphous silicon pattern  226 . The first and second active layers  120   a  and  122   a  respectively overlap the first and second gate electrodes  202  and  204 , and the first and second impurity-doped amorphous silicon patterns  224  and  226  are respectively disposed on the first and second active layers  120   a  and  122   a.    
         [0070]    Next, as shown in  FIG. 5C  according to yet additional embodiments of the present invention, a second metallic material layer (not shown in the figure) is formed by depositing a second metallic material on the first impurity-doped amorphous silicon pattern  224  (of  FIG. 5B ), the second impurity-doped amorphous silicon pattern  226  (of  FIG. 5B ), and the gate insulating layer  210 . The second metallic material layer may be patterned using various methods, including, but not limited to, a mask process to form the first and second source electrodes  232  and  236 , the first and second drain electrodes  234  and  238 , and the data line  230 . The power line (not shown in the figure) may also be formed to be parallel to the data line  230 . Alternatively, the power line may be formed with the gate line (not shown in the figure) to be parallel to the gate line. For example, the second metallic material layer is formed of a relatively low resistance metallic material, for example, Al, Al alloy, Mo, Cu, Cu alloy, or a mixture thereof. 
         [0071]    The data line  230  crosses the gate line (not shown in the figure) to define the pixel region “P,” and the first source electrode  232  extends from the data line  230 . The first source electrode  232  and the first drain electrode  234  are disposed on the first impurity-doped amorphous silicon pattern  224  (of  FIG. 5B ) and spaced apart from each other. As a result, a center portion of the first impurity-doped amorphous silicon pattern  224  (of  FIG. 5B ) is exposed through the first source electrode  232  and the first drain electrode  234 . In addition, the second source electrode  236  and the second drain electrode  238  are disposed on the second impurity-doped amorphous silicon pattern  226  (of  FIG. 5B ) and spaced apart from each other. As a result, a center portion of the second impurity-doped amorphous silicon pattern  226  (of  FIG. 5B ) is exposed through the second source electrode  236  and the second drain electrode  238 . 
         [0072]    Next, as shown in  FIGS. 5B and 5C  according to further embodiments of the present invention, the center portion of the first impurity-doped amorphous silicon pattern  224  (of  FIG. 5B ) is etched using the first source and drain electrodes  232  and  234  as an etching mask to form the first ohmic contact layer  220   b  and to expose a center portion of the first actively layer  220   a . On the other hand, the center portion of the second impurity-doped amorphous silicon pattern  226  (of  FIG. 5B ) is etched using the second source and drain electrodes  236  and  238  as an etching mask to form the second ohmic contact layer  222   b  and to expose a center portion of the second actively layer  222   a . The first active layer  220   a  and the first ohmic contact layer  220   b  constitute the first semiconductor layer  220 , and the second active layer  222   a  and the second ohmic contact layer  222   b  constitute the second semiconductor layer  222 . 
         [0073]    According to some embodiments of the present invention, the first gate electrode  202 , the gate insulating layer  210 , the first semiconductor layer  220 , the first source electrode  232  and the first drain electrode  234  constitute a switching TFT “STr,” and the second gate electrode  204 , the gate insulating layer  210 , the second semiconductor layer  222 , the second source electrode  236  and the second drain electrode  238  constitute a driving TFT “DTr”. 
         [0074]    Next, as shown in  FIG. 5D  according to yet further embodiments of the present invention, the passivation layer  240  is formed on the data line  230 , the switching TFT “STr” and the driving TFT “DTr”. The passivation layer  240  comprises an inorganic insulating material or an organic insulating material. For example, the inorganic insulating material may include silicon oxide or silicon nitride, and the organic insulating material may include benzocyclobutene (BCB) or photo-acryl. Next, the passivation layer  240  is patterned using various methods, including, but not limited to, a mask process to form the drain contact hole  242  and to expose the second drain electrode  238 . 
         [0075]    Next, a transparent conductive material layer (not shown in the figure) is formed on the passivation layer  240 . The transparent conductive material layer is patterned using various methods, including, but not limited to, a mask process to form the first electrode  250 . The first electrode  250  contacts the second drain electrode  238  through the drain contact hole  242 . Namely, the first electrode  250  is electrically connected to the driving TFT “DTr.” The transparent conductive material may include ITO. Although not shown in the figure, an opaque metallic material layer is formed before forming the transparent conductive material layer. The opaque metallic material layer is also patterned to form the reflective plate. 
         [0076]    Next, as shown in  FIG. 5E , the organic luminescent layer  270  is formed in the pixel region “P.” 
         [0077]    Next, as shown in  FIG. 5F , the second electrode  280  is formed on the organic luminescent layer  270 . The second electrode  280  may include a single layer of Cu or double layers of Ag and Mg. The second electrode  280  may be made thin to be transparent. 
         [0078]    According to some embodiments of the present invention, when the voltage of the power line is applied to the first electrode, the organic luminescent layer  270  emits to display images through the second electrode  280 . When the second source and drain electrodes  236  and  238  of the driving TFT “DTr” are electrically shorted by particles or a static electricity, however, the organic luminescent layer  270  always has an emitting state. Accordingly, an additional process is required to overcome the problem. 
         [0079]    In some exemplary embodiments of the present invention, as shown in  FIG. 5G , the laser beam “LB” is irradiated to the drain contact hole  242  through the image display surface, i.e., the second electrode  280 . In additional exemplary embodiments, the total thickness of the second electrode  280  and the organic luminescent layer  270  is about 3 to 4 micrometers, and the laser beam “LB” of a pulse type has a wavelength of about 532 nm and an energy of about 0.5 to 0.8 mJ. The laser beam “LB” according to additional embodiments of the present invention includes, but is not limited to, a laser having a wavelength between about 300 nm and about 700 nm, about 400 nm and about 600 nm, about 500 nm and about 550 nm, and about 520 nm and about 540 nm. 
         [0080]    By the laser beam “LB” irradiation, as shown in  FIG. 5H , the second electrode  280 , the organic luminescent layer  270  and the first electrode  250  are removed such that the second drain electrode  238  is exposed through the drain contact hole  242 . Namely, the connection of the organic electroluminescent diode and the driving TFT “DTr” is destroyed. Accordingly, the organic luminescent diode has a non-emission state regardless of a state of the switching TFT “STr” and the driving TFT “DTr” such that the brightening point defect problem is overcome. 
         [0081]    As discussed above, the laser beam “LB” of a pulse type may have a wavelength of about 532 nm and an energy of about 0.5 to 0.8 mJ. If the laser bema “LB” is too weak, the connection is incompletely destroyed such that the brightening point defect can not be resolved. On the other hand, if the laser beam is too strong, other elements, for example, the gate line or the data line  230 , is cut such that a darkening point defect is also generated in other pixel regions. With the laser beam “LB”, the connection of the organic electroluminescent diode and the driving TFT “DTr” is completely destroyed by removing the second electrode  280 , the organic luminescent layer  270  and the first electrode  250  without damages on other elements. 
         [0082]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.