Abstract:
A micro electromechanical system (MEMS) array substrate includes a substrate, a plurality of first signal lines, a plurality of second signal lines, a plurality of MEMS switches and a plurality of pixel electrodes. The first signal lines are disposed on the substrate in parallel with one another as well as the second signal lines. The second signal lines intersect with the first signal lines, such that a plurality of pixel regions is defined on the substrate. Each MEMS switch is located at corresponding one of the intersections between the first signal lines and the second signal lines. Each pixel electrode is configured in corresponding one of the pixel regions and electrically connected with the corresponding MEMS switch Compare to thin film transistor, since the operation performance of the MEMS switches would not affected by carrier mobility and on-off current ratio, display performance of the display device can be easily improved. In addition, a display device using the MEMS array substrate is also provided.

Description:
[0001]    This application claims priority to a Taiwan application No. 098123120 filed Jul. 08, 2009. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a display device, and more particular, to a display device with a micro electromechanical system (so-called MEMS) array substrate and the MEMS array substrate thereof. 
         [0004]    2. Description of the Related Art 
         [0005]    With progress of the display technique, more and more electrical products, such as computer, television, monitoring apparatuses mobile phones and digital cameras etc., are equipped with display devices. 
         [0006]    In the present days, thin film transistors are configured in mostly display devices have as driving elements for controlling the operation of display medium. Since the mobility of carries of the inorganic semiconductor materials is larger than that of the organic semiconductor materials, the inorganic semiconductor materials, such as amorphous silicon, is used in conventional thin film transistors. Also, because the amorphous thin film transistors can be fabricated in low temperature, it has become the main stream in the thin film transistor market. 
         [0007]    However, the display performance of the display device is requested more and more, so that the display device has to be provided with the advantages of higher carrier mobility or on-off current ratio. Accordingly, the amorphous thin film transistors could not satisfy the requests of the display device in next generation. 
       BRIEF SUMMARY 
       [0008]    Therefore, the invention is directed to a MEMS array substrate for improving the display performance of display device using the same. 
         [0009]    The invention is also directed to a display device with improved display performance. 
         [0010]    The invention provides a MEMS array substrate including a substrate, a plurality of first signal lines disposed on the substrate in parallel with one another, a plurality of second signal lines disposed on the substrate in parallel with one another, a plurality of MEMS switches and a plurality of pixel electrodes. The second signal lines intersect with the first signal lines, such that a plurality of pixel regions is defined on the substrate. Each MEMS switch is disposed at corresponding one of the intersections between the first signal lines and the second signal lines. Each pixel electrode is configured in corresponding one of the pixel regions and electrically connected with the corresponding MEMS switch. 
         [0011]    The invention provides a display device including the MEMS array substrate, a transparent substrate disposed above the MEMS array substrate and a display medium layer disposed between the MEMS array substrate and the transparent substrate. 
         [0012]    The display device of the invention control the operation of the display medium by the MEMS switches of the MEMS array substrate. Since the material of the MEMS switches is conductive, and the on/off status of the MEMS switches is operated by controlling electric field to make whether the metal layers disposed at different layer electrically connecting to each other or not, the MEMS switches would not have the problems about carrier mobility and the on-off current ratio. This shows that the display device of the invention uses the MEMS switches to increase the display performance thereof. Therefore, the requests in use of the display device in new generation would be satisfied. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
           [0014]      FIG. 1  is a schematic cross-section view of the display device according to an embodiment of the invention. 
           [0015]      FIG. 2  is a schematic top view of a MEMS array substrate of the display device shown in  FIG. 1 . 
           [0016]      FIG. 3  is a schematic cross-section view along the line III-III′ in the  FIG. 2 . 
           [0017]      FIG. 4  is a schematic cross-section view of the MEMS switch shown in  FIG. 3  during the manufacturing process thereof. 
           [0018]      FIG. 5  is a diagram of the MEMS switch shown in  FIG. 4  while there is a voltage differential between the third metal layer and the first metal layer. 
           [0019]      FIG. 6  is a schematic partial cross-section view of the MEMS array substrate according to another embodiment of the invention. 
           [0020]      FIG. 7  is a schematic cross-section view of the MEMS switch shown in  FIG. 6  during the manufacturing process thereof. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  is a schematic cross-section view of the display device according to an embodiment of the invention.  FIG. 2  is a schematic top view of a MEMS array substrate of the display device shown in  FIG. 1 . Referring to  FIG. 1 , the display device  100  includes a MEMS array substrate  10 , a display medium layer  12  and a transparent substrate  14 . The transparent substrate  14  is disposed above the MEMS array substrate  10 , and the display medium layer  12  is disposed between the MEMS array substrate  10  and the transparent substrate  14 . Specifically, the display medium layer  12  is, for example, an electro-phoretic layer or a liquid crystal layer. 
         [0022]    Referring to  FIG. 1  and  FIG. 2 , the material of the transparent substrate  14  is, for example, glass. The MEMS array substrate  10  includes a substrate  101 , a plurality of first signal lines  102 , a plurality of second signal lines  103 , a plurality of MEMS switches  105  and a plurality of pixel electrodes  106 . The first signal lines  102  are disposed on the substrate  101  in parallel with one another as well as the second signal lines  103 . The second signal lines  103  intersect the first signal lines  102  and thus a plurality of pixel regions  104  are defined on substrate  101 . The MEMS switches  105  are disposed at the intersections between the first signal lines  102  and the second signal lines  103 , and the pixel electrodes  106  are disposed on corresponding one of the pixel regions  104  and electrically connected to the MEMS switch  105  corresponding thereto. 
         [0023]    In this embodiment, the first signal lines  102  and the second signal lines  103  are, for example, data lines and scan lines respectively, but not limited hereto. In another embodiment, the first signal lines  102  may be data lines, and the second signal lines  103  may be scan lines. 
         [0024]      FIG. 3  is a schematic cross-section view along the line III-III′ in the  FIG. 2 . Referring to  FIG. 2  and  FIG. 3 , each MEMS switch  105  includes a first metal layer  1051 , an insulating layer  1052 , a second metal layer  1053  and a third metal layer  1054 . The first metal layer  1051  is disposed on the substrate  101  and electrically connected to corresponding one of the first signal lines  102 . The insulating layer  1052  is disposed on the first metal layer  1051 . The second metal layer  1053  is disposed on the insulating layer  1052  and electrically connected to corresponding one of the pixel electrodes  106 . The third metal layer  1054  is disposed on the second metal layer  1053  and electrically connected to corresponding one of the second signal lines  103 . Specially, an insulating cavity  1055  is formed between the third metal layer  1054  and the second metal layer  1053 . 
         [0025]    Further, the MEMS switch  105  is formed by forming the first metal layer  1051 , the insulating layer  1052  and the second metal layer  1053  on the substrate  101  sequentially first. Then, a sacrificial layer  1056  is formed on the second metal layer  1052  and the third metal layer  1054  is formed on the sacrificial layer  1056 , as shown in  FIG. 4 . Later, the sacrificial layer  1056  is removed by gas etch, and thus the MEMS switch  105  shown in  FIG. 3  is formed. The materials of the first metal layer  1051  and the second metal layer  1053  are, for example, silver, chromium, alloys of molybdenum and chromium, alloys of aluminum and neodymium or nickel boride. The material of the insulating layer  1052  is, for example, silicon oxide or silicon nitride. The material of the third metal layer  1054  is magnetic metal, such as nickel/alloys of aluminum and neodymium or nickel boride/alloys of aluminum and neodymium. 
         [0026]    Especially, for simplifying the manufacturing process of the MEMS array substrate  10 , the first metal layer  1051  of each MEMS switch  105  may be formed at the same layer with the first signal lines  102 , the second metal layer  1053  may be formed at the same layer with the pixel electrodes  106  and the third metal layer  1054  may be formed at the same layer with the second signal lines  103 . Accordingly, if the second metal layer  1053  is formed at the same layer with the pixel electrodes, the second metal layer  1053  is made of transparent conductive material, such as indium tin oxide (ITO), indium zinc oxide (IZO) or indium gallium zinc oxide (IGZO). 
         [0027]    The MEMS switch described in the aforementioned embodiments would be taken to be an example to expound the operation of the display device of the invention. 
         [0028]      FIG. 5  is a diagram of the MEMS switch shown in  FIG. 4  while there is a voltage differential between the third metal layer and the first metal layer. Referring to  FIG. 1 ,  FIG. 2  and  FIG. 5 , a voltage differential between the first metal layer  1051  electrically connected to the first signal line  102  and the third metal layer  1054  electrically connected to the second signal line  103  resulted from applying voltage to the first signal line  102  and the second signal line  103  respectively by the driving circuit (not shown) of the display device  100 . At this time, the third metal layer  1054  is expanded downward and contacts the second metal layer  1053  because of being attracted by the electric force induced from the electric field. Thus, the second metal layer  1053  is shorted with the third metal layer  1054  and has the same electric potential with each other. Accordingly, the signals inputted into the second signal line  103  can be transmitted to the pixel electrode  106  through the second metal layer  1053 . Moreover, the operation status of the display medium layer  12  is decided according to the signals transmitted to the pixel electrode  106 . 
         [0029]    On the other hand, when the voltage differential between the first metal layer  1051  and the third metal layer  1054  is 0 V, the attracting force induced from the electric field between the first metal layer  1051  and the third metal layer  1054  would disappear. At this time, the third metal layer  1054  returns to the original status that is electrically insulated with the second metal layer  1053 . Thus, the display status of the display device  100  is returned to the status at the time when the voltage applied to the first signal line  102  and the second signal line not yet. 
         [0030]    Referring to  FIG. 1  and  FIG. 2 , the display device  100  can achieve different display effects by controlling the operation status of the display medium layer  12  corresponding to each pixel region  104  by the MEMS switch  105 . Since the MEMS switch  105  does not have the problems of carrier mobility and the on-off current ratio, the display performance of the display device  100  may be improved. Therefore, the use requests of the display device in new generation may be satisfied. Furthermore, the manufacturing process of the MEMS switch  105  is simpler than that of the amorphous thin film transistor, so that the manufacturing cost of the display device  100  may be reduced. 
         [0031]      FIG. 6  is a schematic cross-section view of the MEMS switch according to another embodiment of the invention. Referring to  FIG. 6 , in the MEMS switch  605  of this embodiment, a supporting layer  1058  with an opening  1057  may be disposed between the third metal layer  1054  and the second metal layer  1053 . The third metal layer  1054  is filled into the opening  1057 , and the insulating cavity  1055  is formed between the supporting layer  1058  and the second metal layer  1053  and corresponding to the opening  1057 . 
         [0032]    In detail, the MEMS switch  605  is formed by forming the first metal layer  1051 , the insulating layer  1052 , the second metal layer  1053  and the sacrificial layer  1056  on the substrate  101  sequentially first. Then, the supporting layer  1058  with the opening  1057  is formed on the sacrificial layer  1056  and the third metal layer  1054  is formed on the supporting layer  1058  and filled into the opening  1057 , as shown in  FIG. 7 . Later, the sacrificial layer  1056  is removed by gas etch, and thus the MEMS switch  605  shown in  FIG. 6  is formed. 
         [0033]    Referring to  FIG. 1 ,  FIG. 2  and  FIG. 6 , a voltage differential between the first metal layer  1051  electrically connected to the first signal line  102  and the third metal layer  1054  electrically connected to the second signal line  103  resulted from applying voltage to the first signal line  102  and the second signal line  103  respectively by the driving circuit (not shown) of the display device  100 . At this time, a portion of the third metal layer  1054  filled into the opening  1057  is expanded downward and contacts the second metal layer  1053  because of being attracted by the electric force induced from the electric field. Thus, the second metal layer  1053  is shorted with the third metal layer  1054  and has the same electric potential with each other. Accordingly, the signals inputted into the second signal line  103  can be transmitted to the pixel electrode  106  through the second metal layer  1053 , and thus the display device  100  may display the pre-determined images. 
         [0034]    It should be noted that since the supporting layer  1058  is disposed between the third metal layer  1054  and the second metal layer  1053  in this embodiment, the third metal layer  1054  can be prevented from bending downward to electrically contact to the second metal layer  1053  when the voltage is applied to the first metal layer  1051  not yet. Therefore, the unusual operation of the display device  100  may be averted. 
         [0035]    In summary, the display device of the invention controls the operation of the display medium by the MEMS switches of the MEMS array substrate. Since the material of the MEMS switches is conductive, and the on/off status of the MEMS switches is operated by controlling electric field to make whether the metal layers disposed at different layer electrically connecting to each other or not, the MEMS switches would not have the problems about carrier mobility and the on-off current ratio. This shows that the display device of the invention uses the MEMS switches to increase the display performance thereof. Therefore, the requests in use of the display device in new generation would be satisfied. 
         [0036]    The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including configurations ways of the recessed portions and materials and/or designs of the attaching structures. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.