Abstract:
A method of fabricating an active matrix organic light emitting diode display is described. A substrate having a light-emitting region and a non-light-emitting region thereon is provided, and pixel structures have been formed in the light-emitting region. A driving IC is formed on the substrate in the non-emitting region and electrically coupled with the pixel structures. A packaging cap is disposed over the substrate and adhered to the substrate. The packaging cap covers the emitting region of the substrate and the driving IC remains being exposed. Since the driving IC is exposed from the packaging cap, the driving IC can be tested or repaired directly when the driving IC is abnormal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the priority benefit of Taiwan application serial no. 91137633, filed Dec. 27, 2002.  
         BACKGROUND OF INVENTION  
         [0002]    1. Field of Invention  
           [0003]    The present invention relates to planar display and the fabrication method. More particularly, the present invention relates to a display of active matrix organic light emitting diode (AMOLED) and the fabricating method.  
           [0004]    2. Description of Related Art  
           [0005]    The organic light emitting diode is a photoelectric device and can convert the electric energy into optical form in high converting efficiency and is usually used in an indicating lamp or a displaying panel. Since the organic light emitting diode has many properties, such as no view angle effect, easy fabrication process, low cost, high response speed, full color capable of operating in a wide temperature range, and satisfying the required characteristics of a display for the multi-media world. In recent years, the organic light emitting diode has been one of the hot research topics.  
           [0006]    Currently, the active matrix organic light emitting diode (AMOLED) has been greatly developed, wherein the AMOLED typically includes an organic light emitting layer formed over a substrate having a thin film transistor (TFT) array already formed thereon and a cathode layer. In this manner, the AMOLED is driven by the TFT for emitting the light. The convention fabrication method for the display of AMOLED is as follows.  
           [0007]    [0007]FIG. 1 is a drawing of top view, schematically illustrating a conventional display of AMOLED. FIG. 2 is a drawing of cross-sectional view, schematically illustrating the structure shown in FIG. 1 along the line I-I′.  
           [0008]    Referring to FIG. 1 and FIG. 2, in the conventional fabrication method for the display of AMOLED, a substrate  100  having a light-emitting region  120  and a non-light-emitting region  122  is provided. The light-emitting region  120  of the substrate  100  has already been formed with a number of pixel structures  107  arranged in an array. Each of the pixel structures  107  includes an active device (TFT) and an anode layer  102 , a light emitting layer  104 , and a cathode layer  106 .  
           [0009]    In the conventional method, the active device, used to control the pixel structure, is usually composed of TFT&#39;s, of which one TFT is used for switching action and another TFT is used for driving action. The TFT can be amorphous silicon TFT or the low temperature polysilicon (LTPS) TFT. Since the technology for the LTPS TFT can form the driving circuit on the substrate  100  at the same time, most of current displays of AMOLED are using the LTPS TFT as the active device for the pixel structure.  
           [0010]    In these pixel structures  107 , each one of the pixel structures  107  is controlled by a scan line (not shown) and a data line (not shown). The scan line and the data line, located at two sides of the light-emitting region  120 , continuously extend into the non-light-emitting region  122 , and form a number of fan-out conductive lines  108 . The fan-out conductive lines are used for electrical coupling with the driving circuit formed at the non-light-emitting region  122 .  
           [0011]    Further still, the driving circuit  110  is formed on the substrate  100  at the non-light-emitting region  122 , wherein the driving circuit  110  is electrically coupled with the pixel structures  107  via the fan-out conductive lines  108 . Then, a packaging cap  114  is disposed over the substrate  100  by a sealant (not shown) for adhering together. The packaging cap  114  covers the light-emitting region  120  on the substrate  100  and the region disposed with driving circuit  110 , so as to prevent the devices of the display from being under a humid environment and resulting in the malfunction.  
           [0012]    However, since the fabrication yield for the LTPS TFT is still low, when the driving circuit  110  is abnormal, it is very inconvenient to perform the test or repair on driving circuit  110 , which has been formed inside the packaging cap  114 . Indirectly, the production yield is also reduced.  
         SUMMARY OF INVENTION  
         [0013]    The invention provides a display of AMOLED and the fabrication method, so as to at least solve the conventional disadvantages about inconveniently performing the test or repairing on driving circuit, which has been formed inside the packaging cap.  
           [0014]    The invention provides a method for fabricating a display of AMOLED. The method includes first providing a substrate, which has a light-emitting region and a non-light-emitting region. Also and, a number of pixel structures are formed in the light-emitting region on the substrate. Each of the pixel structures includes an active device, an anode layer, a light emitting layer and a cathode layer. In the invention, the active device includes at least two amorphous silicon TFT&#39;s or at least two LTPS TFT&#39;s. A driving circuit is formed in the non-light-emitting region on the substrate, in which the driving circuit and the pixel structures are electrically coupled by a number of conductive lines. Then, a packaging cap is disposed over the substrate by an adhering material, wherein the packaging cap covers the light-emitting region but the driving circuit remains being exposed. In the invention, the packaging cap can be, for example, a metallic packaging cap or a glass packaging cap.  
           [0015]    The invention also provides a display structure of AMOLED, including a substrate, a driving circuit, and a packaging cap. The substrate has a light-emitting region and a non-light-emitting region. Also and, a number of pixel structures are disposed in the light-emitting region on the substrate. Each of the pixel structures includes an active device, an anode layer, a light emitting layer and a cathode layer. In the invention, the active device includes at least two amorphous silicon TFTs or at least two LTPS TFTs. Also and, a driving circuit is formed in the non-light-emitting region on the substrate, in which the driving circuit and the pixel structures are electrically coupled by a number of conductive lines. Then, a packaging cap is disposed over the substrate and is affixed onto the substrate by adhering, wherein the packaging cap covers the light-emitting region but the driving circuit remains being exposed. In the invention, the packaging cap can be, for example, a metallic packaging cap or a glass packaging cap.  
           [0016]    Since the packaging cap of the AMOLED display in the invention does not cover the driving circuit, when the malfunction occurs on the driving circuit, the test or the repairing on the driving circuit can therefore be directly performed.  
           [0017]    Since the packaging cap of the AMOLED display in the invention does not cover the driving circuit, the size of the packaging cap can be less than the size of the conventional packaging cap. As a result, the mechanical strength of the packaging cap is improved and diffusion path or area, where the humid air can diffuse into, is relatively smaller. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0018]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0019]    [0019]FIG. 1 is a drawing of top view, schematically illustrating a conventional display of AMOLED.  
         [0020]    [0020]FIG. 2 is a drawing of cross-sectional view, schematically illustrating the structure shown in FIG. 1 along the line I-I′.  
         [0021]    [0021]FIG. 3 is a drawing of top view, schematically illustrating a display of AMOLED, according to a first preferred embodiment of this invention.  
         [0022]    [0022]FIG. 4 is a drawing of cross-sectional view, schematically illustrating the structure shown in FIG. 3 along the line II-II′. 
     
    
     DETAILED DESCRIPTION  
       [0023]    [0023]FIG. 3 is a drawing of top view, schematically illustrating a display of AMOLED, according to a first preferred embodiment of this invention; and FIG. 4 is a drawing of cross-sectional view, schematically illustrating the structure shown in FIG. 3 along the line II-II′.  
         [0024]    Referring to FIG. 3 and FIG. 4, in the method of the invention to fabricate the display of AMOLED, a substrate  100  is provided. The substrate  100  has a light-emitting region  120  and a non-light-emitting region  122 . The light-emitting region  120  of the substrate  100  has already been formed with a number of pixel structures  107  arranged in an array. Each of the pixel structures  107  includes an active device (TFT) and an anode layer  102 , a light emitting layer  104 , and a cathode layer  106 .  
         [0025]    Here, the active device of the pixel structure  107  includes at least two TFTs. In the embodiment, the active device, for example, is composed of two TFTs, of which one TFT is used for switching action and another TFT is used for driving action. The TFTs can be amorphous silicon TFTs or the low temperature polysilicon (LTPS) TFTs. In addition, in the pixel structures  107 , each one of the pixel structures  107  is controlled by a scan line (not shown) and a data line (not shown). The scan line and the data line, located at two sides of the light-emitting region  120 , continuously extend into the non-light-emitting region  122 , and form a number of fan-out conductive lines  108 . The fan-out conductive lines  108  are used for electrical coupling with the driving circuit formed at the non-light-emitting region  122 .  
         [0026]    In addition, the non-light-emitting region  122  on the substrate  100  has a driving circuit  110  formed thereon, wherein the driving circuit  110  is electrically coupled with the pixel structures  107  via the fan-out conductive lines  108 .  
         [0027]    It should be noted that when the pixel structures  107  are formed using the LTPS TFTs as the active device, the driving circuit  110  and the active device of the pixel structures  107  can be formed on the substrate  100  using the same fabrication process. In other words, the driving circuit can be composed of the TFTs.  
         [0028]    However, with respect to the display of AMOLED in high resolution and operated in ultrahigh frequency, the driving circuit  110  may not be achieved only by using the LTPS TFTs. Instead, a semiconductor circuit using the single crystal silicon is necessary to be used. In this manner, some part of the devices, not being affected by the frequency, can be directly formed on the substrate  100 . Then, an electric coupling member, which is usually not affected by the frequency, can be used to connect to an external circuit (a semiconductor circuit using the single crystal silicon) for providing the high frequency signals. The driving circuit  110  is thereby formed.  
         [0029]    After then, a packaging cap  200  is disposed on the substrate  100 . The packaging cap  200  is, for example, affixed to the substrate  100  by a sealant (not shown) for adhering to the substrate  100 . The packaging cap  200  covers the light-emitting region  120 , and allows the driving circuit  110  on the substrate  100  to be exposed. Here, the packaging cap  200  can be, for example, a metallic packaging cap or a glass packaging cap.  
         [0030]    The display of AMOLED in the invention includes a substrate  100 , a driving circuit  110 , and a packaging cap  200 .  
         [0031]    The substrate  100  has a light-emitting region  120  and a non-light-emitting region  122 . The light-emitting region  120  of the substrate  100  has already been formed with a number of pixel structures  107  arranged in an array. Each of the pixel structures  107  includes an active device (TFT) and an anode layer  102 , a light emitting layer  104 , and a cathode layer  106 . In the invention, the active device includes, for example, at least two amorphous silicon TFTs or at least two LTPS TFTs.  
         [0032]    In addition, the driving circuit  110  is disposed on the substrate  100  in the non-light-emitting region  122 , wherein the driving circuit  110  and the pixel structures  107  are electrically coupled together via a number of conductive lines  108 . The driving circuit  110  is, for example, composed of a number of TFTs or is composed of TFTs and a semiconductor circuit with single crystal silicon.  
         [0033]    Furthermore, the packaging cap  200  is disposed above the substrate  100  and is adhered to the substrate  100 , wherein the packaging cap  200  covers substrate  100  at the light emitting region  120  but leaves the driving circuit  110  being exposed. In the invention, the packaging cap  200  can be, for example, a metallic packaging cap or a glass packaging cap.  
         [0034]    In the invention, the driving circuit  110  is not covered by the packaging cap  200 . In other words, the driving circuit  110  is formed outside from the packaging cap  200 . When a malfunction occurs on the driving circuit  110 , the driving circuit  110  can be directly tested or repaired, so as to improve the product yield.  
         [0035]    Particularly, when the display of AMOLED is operated in high resolution and in ultrahigh frequency, the driving circuit  110  may not be achieved only using the LTPS TFTs. In this situation, some part of the devices, not being affected by the frequency, can be directly formed on the substrate  100 . An external circuit (a semiconductor circuit using the single crystal silicon) connected to the part of the devices is used to provide the high frequency signals. The driving circuit  110  is thereby formed. Since the semiconductor circuit using the single crystal silicon cannot be directly formed on the substrate  100 , it is necessary to be formed outside from the packaging cap  200 . Therefore, if the device not being affected by the frequency and the semiconductor circuit using the single crystal silicon, which form the complete driving circuit  110 , are all disposed outside the packaging cap  200 , the signal decay between the two kinds of circuits can be reduced. As a result, it is the optimized choice that both the two kinds of circuits are disposed outside the packaging cap  200 .  
         [0036]    In addition, the packaging cap  200  of the AMOLED display in the invention is only covering the light-emitting region  120  on the substrate  100  but not covering the driving circuit  110  on the substrate  100 . In this manner, the size of the packaging cap  200  is less than the size of the conventional packaging cap. The reduced size of the packaging cap  200  has at least two advantages. One is that the packaging cap  200  by smaller size has higher mechanical strength, so that it can more effectively protect the internal device from being damaged by the external impact force. Another one is that the packaging cap  200  by smaller size has the smaller area being adhered to the substrate  100 , resulting in reducing the diffusion path or diffusion area, where the humid air may be diffused into.  
         [0037]    In conclusions, the invention includes several advantages as follows: 1. For the display of AMOLED of the invention, since the packaging cap does not cover the driving circuit, when a mal function or abnormal situation occurs on the driving circuit, the driving circuit can be directly tested or repaired. 2. For the display of AMOLED of the invention, since the packaging cap covers the light-emitting region but not covers the driving circuit, the size of the packaging cap is less than the size of a conventional packaging cap. The mechanical strength is relative higher and the diffusion path or area by the humid air into the cap is also reduced.  
         [0038]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention covers modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.