Patent Publication Number: US-2004055433-A1

Title: Test piece cutter and splitting method thereof

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to an apparatus and method for precisely splitting a test piece.  
       [0003] 2. Description of the Related Art  
       [0004] Semiconductor substrates are usually damaged by particles in the air, failure of fabrication apparatus, or operator fault. In order to increase the yield and reduce the cost, the defective substrates are usually scanned and analyzed to isolate the problem.  
       [0005] Focused ion beams (FIB) are usually used in conventional cross-section analysis. FIG. 1A shows a schematic view thereof, and FIG. 1B is a top view of the test piece shown in FIG. 1A. In FIGS. 1A and 1B, the conventional analysis method uses a focused ion beam  21  to form a groove  13  crossing over a defect P, or a target point, through the wiring layers  12  and the substrate  11 . After that, an electron microscope  30  is used to obliquely scan the microstructure of the cross-section near the target point P. However, the ion beam producer  20  used in the conventional FIB method is very expensive, and its cutting speed is too slow (about 2-5 μm/hr) to form a groove longer than 20 mm.  
       [0006] Because the groove  13  is formed by ion beam  21  and not by cutting though the test piece  10 , the electron beam  31  emitted by the electron microscope  30  can only scan the cross-section from an oblique direction in a predetermined range (19°-81°). Moreover, because the scanning direction is not perpendicular to the cross-section, the received images are not usually clear enough to distinguish each wiring layer.  
       SUMMARY OF THE INVENTION  
       [0007] Accordingly, an object of the present invention is to provide a less expensive but precise cutter for glass test pieces which may have defects and require cross-section analysis.  
       [0008] Another object of the present invention is to provide a method using the cutter to split glass test pieces, such that the cross-section can be vertically observed by an electron microscope, receiving clear images.  
       [0009] The present invention provides a precise cutting device for splitting a test piece. The precise cutting device includes a microscope and a cutter. The microscope has a movable stage and a lens set. The stage supports the test piece. The lens set is adjustable to show the microstructure of the test piece. The cutter disposed under the stage of the microscope can pass through the opening of the stage to form notches on the surface of the test piece.  
       [0010] According to the present invention, the stage of the microscope has a clip to fix the test piece and a first position adjuster to shift the test piece horizontally within a predetermined area.  
       [0011] Moreover, the precise cutting device also has a second position adjuster disposed under the stage to elevate the vertical position of the cutter. The cutter has a diamond tip or a wheel knife at the tip thereof by which can form cuts on the surface of the test piece.  
       [0012] The precise cutting device of the present invention also has an image sensor and a monitor. The image sensor connects to the lens set to receive optical images near the target point on the surface of the test piece. The monitor is electrically connected to the image sensor, showing optical images received by the image sensor converts. The image sensor is a charge-coupled camera.  
       [0013] The present invention also provides a test piece splitting method for the precise cutting device. The method includes the steps of providing a test piece having a surface with a target point and fixed on the stage with the surface contacting the stage and the target point disposed within the range of the opening. The next step of the method is to adjust the amplification of the lens set to show a distinct view of the target point. A first notch and a second notch are formed on the surface. The first notch and the second notch are aligned with the target point in a predetermined line, and the distance between the neighboring end points is a first interval, 1 mm to 50 μm according to a preferred embodiment. Finally, the test piece is split along the predetermined line.  
       [0014] The method to form the notches includes the step of changing the vertical position of the tip of the cutter to contact the surface with target point. Next, the test piece disposed on the stage is moved by the first position adjuster to change the position of the tip to arrive at a first point on the surface. The cutter is raised a second distance, about 50 μm-10 μm, to cut into the test piece. The test piece is moved by the first position adjuster to form a first notch, and then lowering the cutter the second distance. Next, the test piece is moved by the first position adjuster to change the position of the tip to arrive at a second point on the surface. The cutter is raised to cut into the test piece again, forming a second notch.  
       [0015] A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016] The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
     [0017]FIG. 1A is a schematic view showing the conventional cross-section analysis method using a focused ion beam;  
     [0018]FIG. 1B is a top view of the test piece shown in FIG. 1A;  
     [0019]FIG. 2 shows the precise cutting device according to the present invention;  
     [0020]FIG. 3 shows the test piece clipped to the stage;  
     [0021]FIG. 4A is a side view of the cutter with a diamond tip in the first embodiment of the present invention;  
     [0022]FIG. 4B is a side view of the cutter with a wheel knife in the second embodiment of the present invention;  
     [0023]FIG. 5 is a schematic view of the test piece with notches;  
     [0024]FIG. 6 is a flowchart showing the test piece splitting method according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0025]FIG. 2 shows the precise cutting device according to the present invention. The precise cutting device  40  includes a microscope  41  and an elevated cutter assembly  44 . The microscope  40  has a movable stage  43 , an adjustable lens set  42 , and a light source  45 . The stage  43  supports the test piece  10 . The lens set  42  includes eyepieces  421  and objectives  422  to change the amplification of the microscope  41 , showing the microstructure of the test piece  10 . The light source disposed on the base  49  of the microscope  41  has a lamp facing the opening  431  of the stage  43  to light the test piece  10 .  
     [0026] The cutter assembly  44  is disposed on the base  49  under the stage of the microscope and aligned with the opening  431 . The cutter assembly  44  includes a second position adjuster  442  and an extendable cutter  441  disposed thereon. The second position adjuster  442  can be rotated to vertically raise or lower the cutter  441 . The tip of the cutter  441  passes through through-hole  431  of the stage  43  contacting the bottom surface of the test piece  10  on the stage  43  to form notches. The precise cutting device  40  according to the present invention further includes an image sensor  46  and a monitor  47  to display a clear image of the test piece  10 . The image sensor is a charge-coupled camera. The image sensor disposed on the eyepiece side of the lens set  42  electrically connects to the monitor  47 , converting received optical images into electrical signals, such s that an enlarged view of the test piece  10  can be displayed on the monitor  47 .  
     [0027]FIG. 3 shows the test piece clipped to the stage. In FIG. 3, the stage  43  of the microscope  41  includes a top plate  43   a  and an immovable bottom plate  43   b.  The top plate  43   a  and the bottom plate  43   b  each have an opening  431 . The top plate  43   a  also has clips  432  to fix the test piece  10  covering the opening  431 . The target point P is disposed within the area of the opening  431 . A first position adjuster  434  includes an X-position adjuster  434   a  and a Y-position adjuster  434   b,  which can move the top plate  43   a  with respect to the bottom plate  43   b.    
     [0028]FIG. 4A shows a cutter with a diamond tip in the first embodiment. The cutter assembly  44  includes a second position adjuster  442  and a cutter  441  disposed thereon. The first preferred cutter  441  has a diamond tip  441   a.  When rotating the second position adjuster  442  to raise the cutter  441  the diamond tip  441   a  contacts the bottom surface of the test piece  10  clipped to the top plate  43   a,  and test piece  10  is moved with respect to the diamond tip  441   a,  forming notches for subsequent splitting. In FIG. 4B, the second preferred cutter  441  of the cutter assembly  44 ′ has a wheel knife  441   b.  The wheel knife  441   b  can only be used in a predetermined direction because of the fixed rotating direction. However, the notches formed by the wheel knife  441   b  are straight, such that the cross-section formed by the next splitting method can precisely cross the target point P.  
     [0029]FIG. 5 is a schematic view of the test piece with notches, and FIG. 6 is a flowchart showing the test piece splitting method of the present invention. Referring to FIGS.  2 - 3  and  5 - 6 , the present invention provides an operating method of the precise cutting device  40  to split a transparent test piece, such as a piece of the glass substrate of an LCD panel. First, the method includes the steps of providing a rectangular test piece of a proper size (S 601 ). The test piece  10  has wiring layers (ITO) with a target point P requiring cross-section analysis. Next, the surface  12  of the wiring layers acts as a contact surface. The test piece  10  is fixed on the stage  43  by the clips  432  with the surface  12  contacting the top plate  43   a  (S 602 ). The target point P is disposed within the range of the opening  431 . A proper amplification of the lens set  41  is made and the height of the stage  43  is modified by the focus adjustment  433  to show a distinct view of the target point P (S 603 ). Next, the cutter  441  is raised, and the tip of the cutter  441  passes through the opening  431 , touching the surface  12  of the test piece  10  (S 604 ). At the same time, the tip of the cutter  441  can be seen through the microscope  41 . Next, the test piece  10  on the stage  43  is horizontally shifted by the X-position adjuster  434   a  and the Y-position adjuster  434   b,  such that the tip of the cutter  441  arrives at a first point Q (S 605 ). The cutter  441  is raised a second distance d 2  to cut into the wiring layers  12  and the glass substrate  11  of the test piece  10  (S 606 ). The test piece  10  fixed on the top plate  43   a  is moved in a straight line along the X-direction to form a first notch C 1  (S 607 ). The cutter  441  is lowered a second distance d 2  (S 608 ). Furthermore, the test piece  10  on the stage  43  is horizontally shifted again, such that the tip of the cutter  441  arrives at a second point R(S 609 ). The cutter  441  is raised a second distance d 2  to cut into the wiring layers  12  and the glass substrate  11  of the test piece  10  (S 610 ). The test piece  10  fixed on the top plate  43   a  is moved in a straight line along the X-direction to form a second notch C 2  (S 611 ). Finally, the test piece  10  is split by hand or a predetermined mechanism along the first notch C 1  and the second notch C 2 , acquiring a neat cross-section through the target point P.  
     [0030] In FIG. 5, the first point P and the second point Q are the closest points to the target point P of the first notch C 1  and the second notch C 2 . The first point Q, the target point P and the second point R are aligned in the same line. The interval between the first point Q and the second point R are a first distance, about 1 mm to 50 μm. The depth of the first notch C, and the second notch C 2  is the second distance, about 1 mm to 50 μm.  
     [0031] According to the precise cutting device and the splitting method of the present invention, operators can split glass test pieces by modifying a standard inexpensive optical microscope. The splitting procedure can be finished in about 10 minutes, thus greatly shortened.  
     [0032] Furthermore, by the precise cutting device according to the present invention, one of each test piece has a neat cross-section passing exactly through the defect, or the target point. The cross-section can be scanned by an electron microscope, such that the image of each wiring layer can be easily distinguished, improving the accuracy of the cross-section analysis.  
     [0033] While the present invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the present invention is not limited to the disclosed embodiments. Instead, 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.