Abstract:
The present invention discloses a method of manufacturing a display unit of a flat display panel having a wide viewing angle. Conventional process, which requires two mask steps for opening contact holes in isolation layers, is improved and merged into only one mask step, whereby the number of masks is reduced from seven to six in fabricating a pixel unit of a FOP LCD panel and the cost of fabrication is also reduced.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a method of manufacturing a display unit of a flat display panel having a wide viewing angle, to reduce the required masks in the fabrication process.  
           [0003]    2. Description of the Related Art  
           [0004]    Liquid crystal display panels (hereinafter referred to as LCD panels) are among the most popular flat display panels. Recently, LCD panels of the fringe field switch (FFS) type have been developed. Generally a display unit (or pixel unit) in a LCD panel of the FFS type has pixel electrodes and common electrodes, which are made of transparent indium-tin oxide layers (hereinafter referred to as ITO layers), thereby increasing the brightness of the LCD panel. The pixel electrodes of the display unit in the FFS-type LCD panel are formed in a comb shape or a multi-finger shape and the common electrodes of the FFS-type LCD panel are formed in a plate shape. In addition, pixel electrodes of comb shape or multi-finger shape generally are provided over the common electrodes.  
           [0005]    The electrode structure of a display unit in an FFS-type LCD panel is prevalent in fabricating a LCD panel having a wide viewing angle. The LCD panel having a wide viewing angle, for instance the IPS (in-plane switch) LCD panel or FOP (finger-on-panel) LCD panel, has a similar electrode structure to that of the FFS-type LCD panel. The electrode structure of the FOP LCD panel requires two fabricating processes for ITO layers, therefore increasing the number of masks and the manufacturing cost.  
           [0006]    [0006]FIGS. 1A to  1 G show, in a cross-sectional view, the process of fabricating a pixel unit of a FOP LCD panel having a wide viewing angle in a conventional art.  
           [0007]    First, a first metal layer (M 1 ) is formed on a substrate  100 , for example, a glass substrate. Secondly, a first photolithography process (using the first mask) is carried out to pattern and then etch the first metal layer (M 1 ) to form a gate layer  101  and a bottom electrode layer  102  on the substrate  100 , as depicted in FIG. 1A.  
           [0008]    A first isolation layer  103  is formed over the substrate  100 . Then, an active layer is formed on the first isolation layer  103 . The active layer, for example, is an amorphous silicon layer or a polysilicon layer.  
           [0009]    A second photolithography process (using the second mask) is carried out to pattern and then etch the active layer to form an island-like layer  104  overlaying the gate layer  101 , as depicted in FIG. 1B.  
           [0010]    Then, a second metal layer (M 2 ) is formed over the substrate  100 .  
           [0011]    A third photolithography process (using the third mask) is carried out to pattern and then etch the second metal layer (M 2 ) to form a first source/drain electrode  105 , a second source/drain electrode  106 , a top electrode layer  107 , and a common contact layer  108 , as depicted in FIG. 1C.  
           [0012]    It is noted that the first and second source/drain electrodes ( 105 ,  106 ) respectively overlap side portions of the island-like layer  104  and the island-like layer  104  is revealed between the first and second source/drain electrodes ( 105 ,  106 ). The bottom electrode layer  102 , the top electrode layer  107 , and the first isolation layer  103  constitute a storage capacitor of the pixel unit in the FOP LCD panel.  
           [0013]    A second isolation layer (referred to as a planarization layer)  109  is then formed over the substrate  100 .  
           [0014]    A fourth photolithography process (using the fourth mask) is further carried out to pattern and then etch the second isolation layer  109  to reveal the first source/drain electrode  105  and the top electrode layer  107 , as depicted in FIG. 1D.  
           [0015]    Next, a first ITO layer is formed on the second isolation layer  109 .  
           [0016]    A fifth photolithography process (using the fifth mask) is carried out to pattern and then etch the first ITO layer so as to form a common electrode layer  110 , as depicted in FIG. 1E. The common electrode layer  110  is electrically connected to both the first source/drain electrode  105  and the top electrode layer  107 .  
           [0017]    Next, a planarized isolation layer  111  and a TEOS layer  112  are sequentially formed over the substrate  100 . Then, a sixth photolithography process (using the sixth mask) is carried out to pattern and then etch the TEOS layer  112  and the planarized isolation layer  111  so as to reveal the common contact layer  108 , as depicted in FIG. 1F.  
           [0018]    A second ITO layer is formed on the TEOS layer  112 . A seventh photolithography process (using the seventh mask) is carried out to pattern and then etch the second ITO layer so as to form pixel electrodes, as depicted in FIG. 1G. The pixel electrodes form in a multi-finger shape or a comb shape.  
           [0019]    It is obvious from the above descriptions that seven masks are required to fabricate a display unit of a FOP LCD panel. Seven masks are more than that required to fabricate the FFS-type TFT LCD panel and more costly.  
         SUMMARY OF THE INVENTION  
         [0020]    Therefore, an object of the present invention is to provide a method of manufacturing a display unit of a flat display panel having a wide viewing angle while reducing the number of masks and the cost of fabrication.  
           [0021]    The present invention achieves the above-indicated objects by providing a method comprising the following steps.  
           [0022]    (a) Form a first conduction layer on a substrate.  
           [0023]    (b) Pattern and etch the first conduction layer to form a gate layer and a bottom electrode layer on the substrate.  
           [0024]    (c) Form a first isolation layer on the substrate.  
           [0025]    (d) Form an active layer on the first isolation.  
           [0026]    (e) Pattern and etch the active layer to form an island-like layer over the gate layer.  
           [0027]    (f) Form a second conduction layer over the substrate.  
           [0028]    (g) Pattern and etch the second conduction layer to form a first and second source/drain electrodes, a top electrode layer, and a common contact layer. It is noted that the first and second source/drain electrodes respectively overlap side portions of the island-like layer revealing the island-like layer therebetween, and the bottom electrode layer, the first isolation layer, and the top electrode layer constitute a storage capacitor of the displaying unit of the flat display panel.  
           [0029]    (h) Form a second isolation layer over the substrate.  
           [0030]    (i) Form a third conduction layer on the second isolation layer.  
           [0031]    (j) Pattern and etch the third and second isolation layers to form a first contact hole, a second contact hole, a third contact hole, a fourth contact hole, and at least a fifth contact hole. It is noted that the first source/drain electrode is revealed in the first contact hole, the common electrode layer is revealed in the second and third contact holes, the top electrode layer is revealed in the fourth contact hole, and the common contact layer is revealed in the fifth contact hole.  
           [0032]    (k) Form a third isolation layer over the substrate.  
           [0033]    (l) Pattern and etch the third and second isolation layers to form a first contact hole, a second contact hole, a third contact hole, a fourth contact hole, and at least a fifth contact hole. It is noted that the first source/drain electrode is revealed in the first contact hole, the common electrode layer is revealed in the second and third contact holes, the top electrode layer is revealed in the fourth contact hole, and the common contact layer is revealed in the fifth contact hole.  
           [0034]    (m) Form a fourth conduction layer on the third isolation layer and respectively fill in the first to fifth contact holes.  
           [0035]    (n) Pattern and etch the fourth conduction layer to form a plurality of pixel electrodes, a first connecting layer, and a second connecting layer on the third isolation layer. It is noted that the first source/drain electrode in the first contact hole and the common electrode layer in the second contact hole are electrically connected via the first connecting layer, the common electrode layer in the third contact hole and the top electrode layer in the fourth contact hole are electrically connected via the second connecting layer, and the pixel electrodes electrically connect to the common contact layer through the fifth contact hole. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]    The following detailed description, given by way of example and not intended to limit the invention solely to the embodiments described herein, will best be understood in conjunction with the accompanying drawings, in which:  
         [0037]    [0037]FIGS. 1A to  1 G show, in a cross-sectional view, the process of fabricating a pixel unit of a FOP LCD panel having a wide viewing angle in a conventional art;  
         [0038]    [0038]FIG. 2 shows the layout of a pixel unit in a TFT LCD panel manufactured according to the present invention;  
         [0039]    [0039]FIGS. 3A to  3 F show the fabricating process of the pixel unit of the LCD panel (FIG. 2) according to a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0040]    [0040]FIG. 2 shows the layout of a pixel unit in a TFT LCD panel manufactured according to the present invention. Referring to FIG. 2, a thin film transistor (TFT)  201  serving as a switching device is disposed near the cross section of a scanning line  202  and a data line  203  in the pixel unit. A common electrode layer  204  at the bottom of the pixel unit is in the shape of a plate. A plurality of pixel electrodes  205  at the top of the pixel unit are in the shape of a comb or fingers. The pixel electrodes  205  are mutually disposed in parallel, and electrically connected together via at least a common contact (not shown in FIG. 2). The common electrode layer  204  electrically connects to the first source/drain electrode  207  of the TFT  201  via a first connecting portion  206 . The top electrode of a storage capacitor  209  electrically connects to the common electrode layer  204  via a second connecting portion  208 .  
         [0041]    [0041]FIGS. 3A to  3 F show the fabricating process of the pixel unit of the LCD panel (FIG. 2) according to a preferred embodiment of the present invention. In FIGS. 3A to  3 F, the region I shows a cross sectional view of the TFT  201  taken along line A-A′ in FIG. 2; the region II shows a cross sectional view of the electrode structure taken along line B-B′ in FIG. 2; the region III shows a cross sectional view of the storage capacitor  209  taken along line C-C′ in FIG. 2; and the region IV shows the region forming the common contact (not shown in FIG. 2) in a cross sectional view.  
         [0042]    The method of fabricating the pixel unit of the LCD panel in FIG. 2 comprises the following steps.  
         [0043]    First, form a first conduction layer, for example a first metal layer (metal- 1 ), on a substrate  300 . The substrate is a glass substrate or a quartz substrate.  
         [0044]    Carry out the first photolithography process (using the first mask) to pattern and etch the first metal layer (metal- 1 ), thereby forming a gate layer  301  and a bottom electrode layer  302  on the substrate  300 , as depicted in FIG. 3A.  
         [0045]    Form a first isolation  303  over the substrate  300 . Next, form an active layer on the first isolation layer  303 . The active layer is an amorphous silicon layer or a polysilicon layer.  
         [0046]    Carry out the second photolithography process (using the second mask) to pattern and etch the active layer, thereby forming an island-like layer  304  over the gate layer  301 , as depicted in FIG. 3B.  
         [0047]    Further, form a second conduction layer, for example a second metal layer (metal- 2 ), over the substrate  300 .  
         [0048]    Although the first and second conduction layers are metal layers in this embodiment, they also can be polysilicon layers.  
         [0049]    Carry out the third photolithography process (using the third mask) to pattern and etch the second metal layer (metal- 2 ), thereby forming a first source/drain electrode  305 , a second source/drain electrode  306 , a top electrode layer  307 , and a common contact layer  308 , as depicted in FIG. 3C.  
         [0050]    It is noted that the first and second source/drain electrodes ( 305 ,  306 ) respectively overlap side portions of the island-like layer  304  . The island-like layer  304 , serving as the channel region of the TFT  201  (FIG. 2), is revealed between the first and second source/drain electrodes ( 305  and  306 ). The bottom electrode layer  302 , the top electrode layer  307 , and the first isolation layer  303  constitute a storage capacitor of the pixel unit in the LCD panel.  
         [0051]    Subsequently, form a second isolation layer  309  over the substrate  300 . Form a third conduction layer, for example a first ITO layer (ITO 1 ), on the second isolation layer  309 .  
         [0052]    Carry out the fourth photolithography process (using the fourth mask) to pattern and etch the first ITO layer (ITO 1 ), thereby forming a common electrode layer  310 , as depicted in FIG. 3D.  
         [0053]    Further, form a third isolation layer  311  over the substrate  300 .  
         [0054]    Then, carry out the fifth photolithography process (using the fifth mask) to pattern and etch the third and second isolation layers ( 311  and  309 ), thereby forming a first opening (or contact hole)(OP 1 ), a second opening (OP 2 ), a third opening (OP 3 ), a fourth opening (OP 4 ), and at least a fifth opening (OP 5 ), as depicted in FIG. 3E.  
         [0055]    It is noted that the first source/drain electrode  305  is revealed in the first opening (OP 1 ), the common electrode layer  310  is revealed in the second and third openings (OP 2  and OP 3 ), the top electrode layer  307  is revealed in the fourth opening (OP 4 ), and the common contact layer  308  is revealed in the fifth opening (OP 5 ).  
         [0056]    Subsequently, form a fourth conduction layer, for example a second ITO layer (ITO 2 ), on the isolation layer  311 , wherein the second ITO layer (ITO 2 ) fills into the first to fifth openings (OP 1 ˜OP 5 ).  
         [0057]    Further, carry out the sixth photolithography process (using the sixth mask) to pattern and etch the second ITO layer (ITO 2 ), thereby forming a plurality of pixel electrodes  312 , a first connecting layer  313 , and a second connecting layer  314  on the third isolation layer  311 , as depicted in FIG. 3F.  
         [0058]    It is noted that the first source/drain electrode  305  in the first opening OP 1  and the common electrode layer  310  in the second opening OP 2  are electrically connected via the first connecting layer  313 . The common electrode layer  310  in the third opening Op 3  and the top electrode layer  307  in the fourth opening OP 4  are electrically connected via the second connecting layer  314 . The pixel electrodes  312  electrically connect to the common contact layer  308  through the fifth opening OP 5 .  
         [0059]    From the above descriptions, the features of the present invention are quite clear. After forming the second isolation layer  309 , no step of forming contact holes (or openings) is immediately carried out, according to the present invention. Instead, the required openings or contact holes (OP 1 ˜OP 5 ) are formed together after forming the third isolation layer  311  and the required circuitry is formed by defining the second ITO layer (ITO 2 ) at the non-pixel and opaque region thereof, whereby only six masks are required to manufacture the pixel unit of the LCD panel and the cost is reduced.  
         [0060]    While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.