Patent Publication Number: US-2007111346-A1

Title: Laser-marking method for a wafer

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to a laser-marking method for a wafer, particularly to a laser-marking method using a frame to support the wafer.  
      2. Description of the Related Art  
      Referring to  FIGS. 1A  to  1 D, they show a conventional laser-marking method for a wafer. Referring to  FIG. 1A , firstly, a wafer  10  is provided. The wafer  10  has a first surface  101  and a second surface  102 , and a plurality of bumps  103  are disposed on the first surface  101 . A glue layer  11  is disposed on the first surface  101 . Referring to  FIG. 1B , the wafer  10  is ground to be thinner. Referring to  FIG. 1C , the glue layer  11  is attached on a first film  12 , and a laser light  13  is projected on the second surface  102  of the wafer  10  to mark the wafer  10 . Referring to  FIG. 1D , finally, the wafer  10  is cut to form a plurality of chips  14 .  
      In the conventional laser-marking method, the first film  12  is not installed on a frame so that the thinned wafer  10  cannot obtain a larger supporting force to support the wafer and the orientation of the laser light  13  cannot be improved. Therefore, the precision for marking the wafer  10  and the quality of products cannot be ensured. In addition, without the frame protection, the thinned wafer  10  is easily broken when the wafer  10  is moved to the printing stage.  
      Consequently, there is an existing need for providing a laser-marking method for a wafer to solve the above-mentioned problems.  
     SUMMARY OF THE INVENTION  
      One objective of the present invention is to provide a laser-marking method for a wafer. The laser-marking method of the invention comprises the steps of: (a) providing a wafer, the wafer having a first surface and a second surface, and a glue layer disposed on the first surface; (b) attaching the glue layer under a first film, the first film installed on a frame; and (c) projecting a laser light on the second surface of the wafer to mark the wafer.  
      In the invention, the first film is installed on a frame so that the thinned wafer can obtain a larger supporting force. Therefore, by utilizing the frame, the supporting force is offered and the orientation of the laser can be improved, so that the precision for marking the wafer and the quality of products can be improved. In addition, the thinned wafer is protected from colliding by the frame, so that the wafer can be prevented from breaking when moved to the printing stage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1A  to  1 D show a conventional laser-marking method for a wafer;  
       FIGS. 2A  to  2 G show a laser-marking method for a wafer according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIGS. 2A  to  2 G, they show a laser-marking method for a wafer according to the present invention. Referring to  FIG. 2A , firstly, a wafer  20  is provided. The wafer  20  has a first surface  201  and a second surface  202 , and a plurality of bumps  203  are disposed on the first surface  201 . A glue layer  21  is disposed on the first surface  201 , and the glue layer  21  is a transparent material. Referring to  FIG. 2B , the wafer  20  is ground to be thinner.  
      Referring to  FIG. 2C , the glue layer  21  is attached on a first film  22 , and the first film  22  is installed on a frame  23 . The shape of the frame  23  matches the shape of the wafer  20 . The first film  22  is a transparent material. The frame  23  is used to protect the wafer  20  to prevent breaking. Referring to  FIG. 2D , a laser light  24  is projected on the second surface  202  of the wafer  20  to mark the wafer  20 , wherein the frame  23  is used to position the laser light  24 . The laser light  24  moves co-axially with an image device (not shown) located on the other side of the wafer  20  to proceed the marking step. Before the wafer  20  is marked, at least one positioning point (not shown) is formed on the second surface  202 . Referring to  FIG. 2E , the wafer  20  and the frame  23  are attached on a second film  25 . Referring to  FIG. 2F , the frame  23  is removed, and then the wafer  20  is cut to form a plurality of chips  26  by using a laser. Referring to  FIG. 2G , finally, the wafer  20  is segregated from the first film  22  and second film  25 .  
      In the invention, the first film  22  is installed on the frame  23  so that the thinned wafer  20  can obtain a larger supporting force. Therefore, by utilizing the frame  23 , a supporting force for the wafer  20  is offered and the orientation of the laser light  24  can be improved, so that the precision for marking the wafer  20  and the quality of products can be improve. In addition, the thinned wafer  20  is protected from colliding by the frame  23 , so that the wafer  20  can be prevented from breaking when moved to the printing stage.  
      While the embodiment of the present invention has been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention may not be limited to the particular forms as illustrated, and that all modifications that maintain the spirit and scope of the present invention are within the scope as defined in the appended claims.