Abstract:
The present invention relates to a method for transferring devices. A sacrificing layer is positioned before the devices are manufactured, and a transition substrate is pasted on the devices. Then, a method for lateral wet etching or a method for lateral wet etching with mechanical stripping is applied for removing or stripping the sacrificing layer so as to separate the devices and a substrate. The separated devices are transferred to the transition substrate so as to meet the requirements for various products and applications.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a method for transferring devices. More particularly, this invention can be applied in transferring the devices to a flexible substrate.  
         [0003]     2. Description of the Prior Art  
         [0004]     As the flat panel display is developed toward large area, the characteristics of lightness, thinness, and flexibility are another trends. The main trend of the development is to use a plastic substrate in place of a glass substrate. Nowadays, the flat panel display is produced on the glass panel for the advantages of great area and mass production, but the substrate has been changed into the plastic substrate when the advantages of lightness, thinness and flexibility are required. However, the process temperature of the thin film transistor liquid crystal display (TFT-LCD) fabrication is 300˜400° C., so the plastic substrate is not applicable to TFT-LCD fabrication. Thus, many alternative methods are developed, particularly, the method of reducing the process temperature and transferring devices. However, the method for reducing the process temperature will affect the characteristic of the device and cause the problems of bad adhesion, lithography over-focus, stress, static electricity and so on. Therefore, the method of transferring devices is more feasible.  
         [0005]     Please refer to  FIGS. 1A-1F .  FIGS. 1A-1F  are perspective diagrams showing steps of a prior art transfer technology disclosed in U.S. Pat. No. 6,127,199. In  FIG. 1A , a light absorption layer  12  is formed on the substrate  10 . In  FIG. 1B , a device layer  14  is formed on the light absorption layer  12 . The detailed description for the device  15  in the device layer  14  will not be described because it is not crucial in this technology. Please refer to  FIG. 1C , an adhesive layer  16  is used to pasting the transferred substrate  18  to the device layer  14 . As shown in  FIG. 1D , The laser light is irradiated through the substrate and the light absorption layer so as to separate the substrate from the light absorption layer. Please refer to  FIG. 1E . Practically, the light absorption layer  12  may be removed together with the substrate  10 . If not, the methods of washing, etching and polishing can be used for removing the light absorption layer  12 , as  FIG. 1F  shown. This is a well-known prior art. However, the drawback is to precisely control the energy of the laser light for preventing the thin-film LCD device from damage.  
         [0006]     Please refer to  FIGS. 2A-2F .  FIGS. 2A-2F  are perspective diagrams showing steps of a prior art transfer technology of devices disclosed in U.S. Pat. No. 6,232,136. As shown in  FIG. 2A , an upper and a lower oxidization layers  34 ,  32  are positioned on the substrate  30 . Besides, an isolation layer  36  is positioned on the upper oxidization layer  34 . Then, a thin film  38  is positioned on the isolation layer  36 , and the devices  40  are formed on the thin film  38 .  FIG. 2B  shows the step for opening a hole  42  on the isolation layer  36  and the upper oxidization layer  34 . Then, as shown in  FIG. 2C , the resin  48  is filled in the opening hole  42 , after the filling, via holes  46  are formed on the isolation layer  36 . Please refer to  FIG. 2D . With the support of the resin  48 , the upper oxidization layer  34  is removed by lateral etching process so as to form the structure with a blank layer  50 . Thereafter, with the support of the resin  48 , the reserved resin  82  and the removed resin  84  are form. Please refer to  FIG. 2E . A transition substrate  80  is further positioned on the reserved resin  82  and the removed resin  84 . Finally, please refer to  FIG. 2F . The removed resin  84  connected to the resin  48  is removed together with a part of the isolation layer  36  so as to complete the process of the transfer.  
         [0007]     The above is the detailed description of the two prior art technologies. However, in order to achieve the object of transferring the devices, the precise controlling for the energy is required and the complicated process has to be handled. Therefore, the practical application is faulty and other technology has to be further developed and applied so as to accomplish the devices transfer.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention relates to a method for transferring devices. The devices are produced on a substrate, and a buffer layer and a metal sacrificial layer are positioned between the substrate and the device. Then, a lateral etching method is used to remove the metal sacrificial layer so as to achieve the object of separation and transferring the devices.  
         [0009]     When transferring the devices, a plurality of etching channels between the devices is formed in the buffer layer by photolithography and etching, wherein the etching channels expose some parts of the sacrificial layer, and then the metal sacrificial layer is etched partially by a first step lateral etching process. Next, a first transition substrate is pasted on the device. Thereafter, by applying a second step lateral etching or the mechanical stripping process, the remaining metal sacrificial layer is removed or stripped so that the devices are separated from the substrate. Thus, the transfer of the devices is finished.  
         [0010]     Alternatively, a pre-patterned metal sacrificial layer is formed on the substrate, and thereafter a buffer layer is deposited on the metal sacrificial layer. With this pre-patterned design, parts of the buffer layer are connected to the substrate to be pillars of the devices, and then the devices are formed on the buffer layer. In the transfer process, a plurality of etching channels between the devices is formed in the buffer layer by photolithography and etching, wherein the etching channels expose some parts of the sacrificial layer. Thereafter, the metal sacrificial layer is removed fully by first lateral etching through the etching channels, and then a first transition substrate is pasted on the devices. Finally, the pillars of the sacrificial layer are removed by a second lateral etching process or stripped by a mechanical stripping process, and therefore the substrate is separated from the devices and the transfer of the devices is accomplished.  
         [0011]     In the two methods mentioned above, after the devices transfer is accomplished, the devices can further be transferred to a second transition substrate. Namely, the second transition substrate is adhesive to the other side of the device so as to promote the usability of the design of transfer.  
         [0012]     With the present invention employed, the device can be easily manufactured and there is no need to change the parameters of the manufacture, and then the devices can be transferred to any substrate desired. The devices with high performance fabricated in high temperature also can be produced by using this invention. Besides, the substrate applied can be recycled and repeatedly used so as to reduce the cost. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The accompanying drawings, which are incorporated in and form part of the specification in which like numerals designate like parts, illustrate preferred embodiments of the present invention and together with the description, serve to explain the principles of the invention. In the drawings:  
         [0014]      FIGS. 3A-3G  are perspective diagrams showing steps of a manufacturing process according to a first embodiment of the present invention; and  
         [0015]      FIGS. 4A-4G  are perspective diagrams showing steps of a manufacturing process according to a second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     The present invention provides a method of transferring devices. By applying the present manufacturing process, after forming the display devices on a substrate, the display devices are transferred on another substrate made of a desired material by the present invention. Therefore, without changing the conditions of the original manufacturing process for the devices, the devices fabricated can be transferred to any desired substrate.  
         [0017]     Embodiment 1  
         [0018]     Please refer to  FIGS. 3A-3G .  FIGS. 3A-3G  are the perspective diagrams showing steps of a manufacturing process according to a first embodiment of the present invention. At the beginning, as shown in  FIG. 3A , a sacrificial layer  110  made of metal material is formed on a substrate  100 , and then a buffer layer  120  is formed on the sacrificial layer  110 , and the required devices  130  is produced and formed on the buffer layer  120 . Thereafter, the transferring of the devices  130  will be performed.  
         [0019]     Please refer to  FIG. 3B . Between the devices  130 , an etching channel  131  is formed in the buffer layer  120  by photolithography and etching. The object is the sacrificial layer  110  can be etched laterally by an etching solution for the sacrificial layer  110  passing through the etching channel  131 . Please refer to  FIG. 3C ;  FIG. 3C  shows that the position of the etching channel  131  is so designed that the extent of the etching for the sacrificial layer can be properly controlled. The sacrificial layer  110  is thus removed partially so as to form sacrificial layer pillars  111 . With the sacrificial layer pillars  111 , the devices  130  can be supported on the substrate  100 .  
         [0020]     Please refer to  FIG. 3D . After the etching of the sacrificial layer  110  is finished and the sacrificial layer pillars  111  are remained, a first transition substrate  140  is pasted on the devices  130 . The first transition substrate  140  can be made of a material with flexibility or a material suitable for other designs.  
         [0021]     As shown in  FIG. 3E , after the first transition substrate  140  is pasted on the devices  130 , the substrate  100  is separated from the sacrificial layer pillars  111 . The method for separating can be mechanical stripping or a lateral etching for the sacrificial layer pillars  111 , wherein the lateral etching for the sacrificial layer pillars  111  is performed in the etching solution for the sacrificial layer  110 . Therefore, the first transfer of the devices  130  is accomplished.  
         [0022]     Thereafter, according to the requirements of the practical applications, a second transfer process can be further performed. Please refer to  FIG. 3F , after finishing the first transfer of the devices  130 , on the other side of the devices  130 , a second transition substrate  150  is pasted on the buffer layer  120 . Please refer to  FIG. 3G , the first transition substrate  140  is removed, and the second transfer of the devices  130  is finished.  
         [0023]     Embodiment 2  
         [0024]     Because the extent of the lateral etching employed for the first embodiment is difficult to control well, so another method for transferring devices is provided. Please refer to  FIGS. 4A-4G .  FIGS. 4A-4G  are the perspective diagrams showing steps of a manufacturing process according to a second embodiment of the present invention.  FIG. 4A  is similar to  FIG. 3A . However, there are some differences between the sacrificial layer  210  and the buffer layer  220 . When positioning the sacrificial layer  210 , the sacrificial layer  210  is formed at a proper position designed, and a plurality of holes is remained. Thereafter, the buffer layer  220  is also formed on the sacrificial layer  210  and fills the holes in the sacrificial layer  210  to form buffer layer pillars  221 . In addition, and then the devices  230  is formed on the buffer layer  220 .  
         [0025]     Then, please refer to  FIG. 4B . Similar to the first embodiment, between the devices  230 , an etching channel  222  is formed in the buffer layer  220  by photolithography and etching. Thereafter, the lateral etching for the sacrificing layer  210  is performed. Please refer to  FIG. 4C . The object of positioning the etching channel  222  is that the sacrificial layer  210  can be etched laterally by an etching solution for the sacrificial layer  210  passing through the etching channel  222 ; therefore, the sacrificial layer  210  is removed fully, and then only the buffer layer pillars  221  are remained to connect the substrate  200  and to support the devices  230 .  
         [0026]     Please refer to  FIG. 4D . After the etching for the sacrificial layer  210  is finished, a first transition substrate  240  is pasted on the devices  230 . Then, please refer to  FIG. 4E ; after the first transition substrate  240  is pasted, the substrate  200  is separated from the buffer layer pillars  221 . The method for separating can be mechanical stripping or a lateral etching for the buffer layer pillars  221 , wherein the lateral etching for the buffer layer pillars  221  is performed in the etching solution for the buffer layer  220 . Thus, the first transfer of the devices  230  is finished.  
         [0027]     Thereafter, according to the requirements of the practical applications, a second transfer process can be further performed. Please refer to  FIG. 4F , after finishing the first transfer of the devices  230 , on the other side of the devices  230 , a second transition substrate  250  is pasted on the buffer layer  220 . Please refer to  FIG. 4G , the first transition substrate  240  is removed, and the second transfer of the devices  230  is finished.  
         [0028]     The above is the detailed description of the present invention. Practically, in the manufacturing process, there is no limitation for the material and the usage of the buffer layer, the sacrificing layer and the transition substrate.  
         [0029]     While the present invention has been disclosed with reference to the preferred embodiments of the present invention, it should not be considered as limited thereby. Various possible modifications and alterations by one skilled in the art can be included within the spirit and scope of the present invention; the scope of the invention is determined by the claims that follow.