Abstract:
A thin film transistor array panel is provided, which includes: a substrate including a plurality of pixel areas; a semiconductor layer formed on the substrate and including a plurality of pairs of first and second semiconductor portions in respective pixel areas; a first insulating layer formed on the semiconductor layer; a gate wire formed on the first insulating layer; a second insulating layer formed on the gate wire; a data wire formed on the second insulating layer; a third insulating layer formed on the data wire; a pixel electrode formed on the third insulating layer and connected to the data wire, wherein width and length of at least one of the first and the second semiconductor portions vary between at least two pixel areas.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     (a) Field of the Invention  
         [0002]     The present invention relates to a TFT array panel, and in particular, to a TFT array panel for an organic electro-luminescence display.  
         [0003]     (b) Description of the Related Art  
         [0004]     Generally, an organic electro-luminescence (EL) display is a self emissive display device, which displays images by exciting an emissive organic material to emit light. The EL display includes an anode (hole injection electrode), a cathode (electron injection electrode), and an organic light emission layer interposed therebetween. When charge carriers are injected into the light emission layer, the electrons and the holes are pair annihilated with emitting light. The EL display further includes an electron transport layer (ETL) and a hole transport layer (HTL) for enhancing the light emission of the light emission layer as well as an electron injecting layer (EIL) and a hole injecting layer (HIL).  
         [0005]     A plurality of pixels of the EL display are arranged in a matrix and driven in simple matrix type or active matrix type with thin film transistors (TFTs).  
         [0006]     The passive matrix type arranges a plurality of anode lines and a plurality of cathode line to intersect each other such that selected one of the anode lines and the one of the cathode lines form a pixel to be driven, while the active matrix type connects TFTs and a capacitor to an anode electrode of each pixel such that the capacitance of the capacitor maintains the voltage of the pixel. A current of a driving TFT for supplying currents to the pixel is controlled by a data voltage supplied through a switching transistor, and a gate and a source of the switching transistor are connected to a gate line (or a scanning line) and a data line intersecting each other. When the switching transistor is turned on by the signal from the gate line, a driving voltage from the data line is applied to the gate of the driving TFT through the switching transistor and the driving TFT supplies a current to the pixels to emit light. The pixels emit red, green and blue lights for color display.  
         [0007]     The EL display severely requires uniformity in device characteristics of the driving TFTs. It is because the difference in the device characteristics of the driving TFTs results in different luminance for the same image data and thus it causes non-uniform luminance of a display screen.  
         [0008]     A most widely used driving TFT for the EL display includes polysilicon channel layer called low temperature polysilicon (LTPS), which is typically formed by eximer laser annealing (ELA) for crystallizing amorphous silicon. However, the polysilicon formed by ELA may have uneven crystallization due to the deviation in ELA energy, which results in non-uniform device characteristics of the TFTs to deteriorate display characteristics of the EL display.  
       SUMMARY OF THE INVENTION  
       [0009]     A motivation of the present invention is to provide a thin film transistor array panel having uniform display characteristics.  
         [0010]     A thin film transistor array panel is provided, which includes: a substrate including a plurality of pixel areas; a semiconductor layer formed on the substrate and including a plurality of pairs of first and second semiconductor portions in respective pixel areas; a first insulating layer formed on the semiconductor layer; a gate wire formed on the first insulating layer; a second insulating layer formed on the gate wire; a data wire formed on the second insulating layer; a third insulating layer formed on the data wire; a pixel electrode formed on the third insulating layer and connected to the data wire, wherein width and length of at least one of the first and the second semiconductor portions vary between at least two pixel areas.  
         [0011]     The thin film transistor array panel may further include: a plurality of partitions for defining the pixel areas; and a plurality of organic light emission a members formed on the pixel electrodes.  
         [0012]     Preferably, the semiconductor layer may further include a plurality of storage electrode portions, the gate wire includes a plurality of first and second gate electrodes and storage electrodes overlapping the first and the second semiconductor portions and the storage electrode portions, respectively, each of the first and the second semiconductor portions has a channel region, a source region, and a drain region, and the data wire includes a plurality of first and, second data lines, a plurality of first source electrodes connected to the first data lines and to the source regions of the first semiconductor portions, a plurality of first drain electrodes connected to the drain regions of the first semiconductor portions and to the second gate electrodes, a plurality of second source electrodes connected to the second data lines and to the source regions of the second semiconductor portions, and a plurality of second drain electrodes connected to the drain regions of the second semiconductor portions and to the pixel electrodes.  
         [0013]     A thin film transistor array panel is provided, which includes: a plurality of first thin film transistors; a plurality of second thin film transistors connected to the first thin film thin film transistors and including channel regions having at least two widths and lengths; and a plurality of pixel electrodes connected to the second thin film transistors.  
         [0014]     The channel regions preferably include polysilicon.  
         [0015]     Each of the first and the second thin film transistors may have a gate, a source, and a drain, and the gates of the second thin film transistors are connected to the drains of the first thin film transistors. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The present invention will become more apparent by describing preferred embodiments thereof in detail with reference to the accompanying drawings in which:  
         [0017]      FIG. 1  is a layout view of a TFT array panel for an EL display;  
         [0018]      FIG. 2  is a sectional view of the TFT array panel shown in  FIG. 1  taken along the line II-II′;  
         [0019]      FIG. 3  is a sectional view of the TFT array panel shown in  FIG. 1  taken along the line III-III′; and  
         [0020]      FIG. 4  is a sectional view of the TFT array panel shown in  FIG. 1  taken along the line IV-IV′. 
     
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
       [0021]     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the inventions are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.  
         [0022]     In the drawings, the thickness of layers and regions are exaggerated for clarity. Like numerals refer to like elements throughout. It will be understood that when an element such as a layer, region or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.  
         [0023]     Now, a TFT array panel according to embodiments of this invention will be described in detail with reference to the accompanying drawings.  
         [0024]      FIG. 1  is a layout view of a TFT array panel for an EL display, and  FIGS. 2, 3  and  4  are sectional views of the TFT array panel shown in  FIG. 1  taker along the lines II-II′, III-III′, and IV-IV′, respectively.  
         [0025]     A semiconductor layer preferably made of polysilicon is formed on an insulating substrate  110 . The semiconductor layer includes a plurality of sets of a semiconductor portion  140  of a switching TFT, a semiconductor portion  142  of a driving TFT, and a storage capacitor portion  146 . Each switching semiconductor portion  140  includes a pair of channel regions  1402  and  1404  and source and drain regions  1401 ,  1403  and  1405  located between and opposite side of the channel regions  1402  and  1404  and doped with n type or p type impurity, while each driving semiconductor portion  142  includes a channel region  1422  and source and drain regions  1423  and  1425  opposite each other with respect to the channel region  1422  and doped with n type or p type impurity.  
         [0026]     According to an embodiment of the present invention, the source and drain regions  1423  and  1425  are doped with p type impurity, while the source and drain regions  1401 ,  1403  and  1405  of the switching TFTs are doped with n type impurity. The channel regions  1422  have different widths w 1 , w 2 , w 3 , w 4 , w 5  and w 6  and lengths d 1 , d 2 , d 3 , d 4 , d 5  and  6   d.    
         [0027]     A blocking layer preferably made of silicon oxide or silicon nitride may be formed under the polysilicon layer  140 ,  142  and  146 .  
         [0028]     A gate insulating layer  130  preferably made of silicon oxide or silicon nitride is formed on the polysilicon layer  140 ,  142  and  146 .  
         [0029]     A gate wire is formed on the gate insulating layer  130 . The gate wire includes a low resistivity conductive layer preferably made of Ag containing metal such as Ag and Ag alloy or Al containing metal such as Al and Al alloy. The gate wire may have a multilayered structure including a low resistivity conductive layer and another layer preferably made of a material having good contact characteristics with other materials.  
         [0030]     The gate wire includes a plurality of gate lines  121  extending in a transverse direction and a plurality of first gate electrodes  123  connected to the gate lines  121  and each first gate electrode  123  includes a pair of switching electrodes  1231  and  1232  overlapping the channel regions  1402  and  1404  of the switching semiconductor portion  140 , respectively. The gate wire further includes a plurality of second gate electrodes  122  separated from the gate lines  121  and overlapping the channel regions  1422  of the driving semiconductor portion  1422 , and a plurality of storage electrodes  124  extending in a longitudinal direction and overlapping the storage capacitor portions  146 . The gate wire- 121 ,  122 ,  123  and  124  may further include a plurality of gate pads connected to ends of the gate lines  121  for transmitting gate signals from an external device to the gate lines  121 . The storage electrodes  124  overlap the storage capacitor portions  146  or second data lines  172 , which will be described later, to form storage capacitors.  
         [0031]     A first interlayer insulating layer  180  preferably made of silicon nitride, silicon oxide or organic insulator is formed on the gate wire  121 ,  122 ,  123  and  124 .  
         [0032]     The gate insulating layer  130  and the first interlayer insulating layer  180  have a plurality of contact holes  1803  and  1805  exposing the source and drain regions  1403  and  1405  of the switching semiconductor portions  140  and they also have a plurality of contact holes  1823  and  1825  exposing the source and drain regions  1423  and  1425  of the driving semiconductor portions  142 . The gate insulating layer  130  and the first interlayer insulating layer  180  further have a plurality of contact holes  1822  exposing the second gate electrodes  122 .  
         [0033]     First and second data wires are formed on the first interlayer insulating layer  180 . The first and the second data wires include a low resistivity conductive layer preferably made of Ag containing metal such as Ag and Ag alloy or Al containing metal such as Al and Al alloy. The data wires may have a multilayered structure including a low resistivity conductive layer.  
         [0034]     The first data wire includes a plurality of first data lines  171  extending in the longitudinal direction and intersecting the gate lines  121  to define a plurality of pixel areas, a plurality of first source electrodes  173  connected to the first data lines  171  and to the source regions  1403  of the switching semiconductor portions  140  through the contact holes  1803 , and a plurality of first drain electrodes  175  separated from the first source electrodes  173  and connected to the drain regions  1405  of the switching semiconductor portions  140  through the contact holes  1805  and to the source regions  1423  of the driving semiconductor portions  142 .  
         [0035]     The second data wire includes a plurality of second data lines  172  extending substantially in the longitudinal direction and overlapping the storage electrodes  124 , a plurality of second source electrodes  174  corrected to the second data lines  172  and to the source regions  1423  of the driving semiconductor portions  149  through the contact holes  1823 , and a plurality of second drain electrodes  176  separated from the second source electrodes  174  and connected to the drain regions  1425  of the driving semiconductor portions  142  through the contact holes  1825 .  
         [0036]     Although it is not shown in the figures, the first and the second data wires may include a plurality of data pads connected to the first and the second data lines  171  and  172  for transmitting electrical signals from an external source to the first and the second data lines  171  and  172 .  
         [0037]     A second interlayer insulating layer  185  having a plurality of contact holes  1855  exposing the second drain electrodes  176  is formed on the data wire  171 ,  172 ,  173 ,  174 ,  175  and  176 , and a plurality of pixel electrodes  192  preferably made of transparent material such as indium tin oxide (ITO) and indium zinc oxide (IZO) are formed on the second interlayer insulating layer  185 . The pixel electrodes  192  are connected to the second drain electrodes  176  through the contact holes  1855  of the second interlayer insulating layer  185 .  
         [0038]     Although it is not shown in the figures, the TFT array panel for an EL, display according to the embodiment of the present invention further includes a          pixel electrodes  192  and a plurality of pixel partitions preferably made of organic material for partitioning the light emission members.  
         [0039]     As described above, the TFT array panel according to the embodiment of the present invention includes the plurality of channel regions  1422  of the driving TFTs provided in the respective pixel areas having different widths w 1 , w 2 , w 3 , w 4 , w 5  and w 6  and different lengths d 1 , d 2 , d 3 , d 4 , d 5  and  6   d . The various widths and lengths of the channel regions of the driving TFTs diversify the driving capacity of the TFTs, and local or global distribution of the driving TFTs with different driving capacities prevents image deterioration of on-screen stripes due to energy deviation of laser beam used for eximer laser annealing (ELA) or sequential lateral solidification for converting amorphous silicon into polysilicon. In particular, the difference in size between grains due to the laser energy difference between shots can be covered by the diversity of the driving capacity of the driving TFTs, thereby keeping uniform image quality.  
         [0040]     Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.