Abstract:
An inking apparatus including an inking head which is manually adjustable in the X, Y and Z directions to facilitate quick and easy positioning of an inking probe in proximity to a defective die on a semiconductor wafer to ink and mark the die for exclusion from further processing. A horizontal positioning plate is horizontally adjustably mounted on a base plate, and an angular adjustment arm is angularly adjustably mounted on the horizontal positioning plate. The inking head is vertically adjustably mounted on the end of the angular adjustment arm and carries an ink reservoir from which ink is dispensed through an inking probe to the dies on the wafer.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to devices used in the testing and inking of dies fabricated on a semiconductor wafer substrate. More particularly, the present invention relates to an inking apparatus which has multi-positioning and adjusting capability in the inking of multiple, disparately-located defective dies on a semiconductor wafer substrate.  
         BACKGROUND OF THE INVENTION  
         [0002]    A conventional method used by the semiconductor industry in the manufacturing of semiconductor integrated circuits includes the steps of fabrication, wafer sort, assembly and test, respectively. In the fabrication step, as many as several thousand dies (integrated circuits) are formed onto a semiconductor wafer. In the wafer sort step, each of the dies on the wafer is tested to determine its electrical characteristics and operability, and defective dies are distinguished from operable dies. The defective dies are often marked by an ink mark at the wafer sorting step. In the assembly step, the unmarked, operable dies are assembled into a package, and in the test step, the packaged integrated circuits are tested for operability and reliability.  
           [0003]    At the wafer sort step, the dies are tested to establish which dies on the wafer function properly. Each die is tested to all functional product specifications for both DC and AC parameters. Four testing objectives are pursued: (1) chip functionality, in which all chip functions are tested to ensure that only fully-functional chips are assembled and packaged in subsequent steps; (2) chip sorting, in which chips are separated or sorted on the basis of their operating speed performance under various voltage and timing conditions; (3) fab yield response, which yields important information that may lead to improvements in the overall fabrication process; and (4) test coverage, in which high test coverage of the internal device nodes is achieved at the lowest possible cost. The wafer sort procedure is similar to the in-line parametric test except that every die on the wafer is tested, in many cases using the same automated test equipment (ATE). Furthermore, the wafer sort procedure is usually located in a separate facility under less stringent purity conditions than those in which the parametric test is carried out, since wafer fabrication is essentially complete.  
           [0004]    In automated wafer handling during wafer sort, a correlation wafer is used to verify tester setup. The correlation wafer is a control wafer the functionality of which has been verified and ensures that the testing system is working properly. After indexing from the cassette to the prober, the wafers are mounted on a vacuum chuck with Z (vertical) positioning. Using software, mechanical probe needles are aligned and contacted with bond pads on the wafer to establish electrical communication between the testing equipment and the dies on the wafer. The probes are interfaced with the ATE to perform the range of AC functional tests based on test algorithms. The type, number and order of tests are defined by the test program.  
           [0005]    After testing, die found to be defective are labeled in a computer database to exclude the die from subsequent packaging steps. The labeling method is typically performed by placing a drop of ink on each unacceptable die. Because the ink marking process can be messy and introduce possible contaminants onto the chip, electronic wafer maps are increasingly being used to create a computer image of chip location and test results to categorize good and bad die on the wafer. At the chip assembly stations, the electronic wafer maps are downloaded into an equipment database to ensure that defective chips will not be packaged.  
           [0006]    Typically, the die on a wafer are inked by operation of an inking head the position of which over the wafer is automatically controlled using a software-actuated controller. In the inking of multiple dies at separate locations on the wafer, the ink head must be moved between multiple positions on the wafer by operation of the software-controlled controller. However, this procedure is time-consuming and inefficient. An apparatus is therefore needed which facilitates manual multi-positioning capability of the ink head over the wafer for inking multiple, disparately-spaced die on the wafer.  
         SUMMARY OF THE INVENTION  
         [0007]    An object of the present invention is to provide an inking apparatus which has multi-positioning capability in the inking of defective dies on a semiconductor wafer.  
           [0008]    Another object of the present invention is to provide an inking apparatus which may be manually-operated.  
           [0009]    Still another object of the present invention is to provide an inking apparatus which reduces the amount of time required for inking multiple dies on a semiconductor wafer.  
           [0010]    Yet another object of the present invention is to provide an apparatus which facilitates quick and yet accurate adjustment of an inking probe in the inking of defective dies on a semiconductor wafer.  
           [0011]    A still further object of the present invention is to provide an apparatus having an inking head which can be adjusted in the X, Y and Z directions as needed in inking multiple, disparately-located, defective dies on a semiconductor wafer.  
           [0012]    In accordance with these and other objects and advantages, the present invention comprises an inking apparatus including an inking head which is manually adjustable in the X, Y and Z directions to facilitate quick and easy positioning of an inking probe in proximity to a defective die on a semiconductor wafer to ink and mark the die for exclusion from further processing. A horizontal positioning plate is horizontally adjustably mounted on a base plate, and an angular adjustment arm is angularly adjustably mounted on the horizontal positioning plate. The inking head is vertically adjustably mounted on the end of the angular adjustment arm and carries an ink reservoir from which ink is dispensed through an inking probe to the dies on the wafer. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0014]    [0014]FIG. 1 is a perspective view of an illustrative embodiment of the present invention;  
         [0015]    [0015]FIG. 2 is a top view of the horizontal positioning plate and angular adjustment arm (in phantom) elements of the present invention, more particularly illustrating an illustrative technique for adjustably mounting the angular adjustment arm on the horizontal positioning plate;  
         [0016]    [0016]FIG. 3 is a side view of the base plate, horizontal positioning plate and angular adjustment arm elements, in section, of the present invention, more particularly illustrating a rack and pinion technique as one example of a mechanism for facilitating horizontal adjustment of the horizontal positioning plate on the base plate;  
         [0017]    [0017]FIG. 4 is a side view of the inking head element of the present invention, more particularly illustrating a rack and pinion technique as one example of a mechanism for vertically adjustably mounting the inking head on the apparatus;  
         [0018]    [0018]FIG. 5 is a side view of the apparatus of the present invention, with the inking head element of the apparatus disposed in a raised position above a semiconductor wafer preparatory to inking a die or dies on the wafer;  
         [0019]    [0019]FIG. 6 is a side view of the apparatus of the present invention, with the inking head shown lowered into contact with the semiconductor wafer in a typical die-inking operation;  
         [0020]    [0020]FIG. 7 is a side view of the apparatus of the present invention, with the inking head shown adjusted to a horizontally-forward position with respect to the position illustrated in FIG. 6; and  
         [0021]    [0021]FIG. 8 is a top view of the apparatus of the present invention, more particularly illustrating multiple alternative positions of the angular adjustment arm in the inking of dies on a semiconductor wafer. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Referring initially to FIGS.  1 - 4  and  8  of the drawings, an illustrative embodiment of the inking apparatus of the present invention is generally indicated by reference numeral  1 . The inking apparatus  1  includes a base plate  2 , on which is slidably mounted an elongated horizontal positioning plate  3  by techniques known by those skilled in the art. A horizontal positioning knob  4  includes a knob shaft  5  which extends through a horizontal shaft opening (not illustrated) provided in the side of the base plate  2 . As illustrated in FIG. 3, a pinion  6  fitted with multiple pinion teeth  7  is mounted on the knob shaft  5 , and the pinion teeth  7  mesh with the multiple rack teeth  9  of a horizontal positioning rack  8  provided on the bottom surface of the horizontal positioning plate  3 . Accordingly, as further illustrated in FIG. 3, the horizontal positioning plate  3  is mounted for bidirectional horizontal sliding movement on the underlying base plate  2  as the horizontal positioning knob  4  is rotated in the clockwise or counterclockwise direction to progressively mesh the pinion teeth  7  with the rack teeth  9 . In a typical embodiment, the horizontal positioning rack  8  may be 4000 mm in length to facilitate a 4000 mm extension of the horizontal positioning plate  3  with respect to the base plate  2 .  
         [0023]    As further illustrated in FIG. 1, an elongated angular adjustment arm  20  is pivotally mounted on the upper surface of the horizontal positioning plate  3  by means of a pivot pin  21 . An angular adjustment knob  16  includes a knob shaft  17  which extends through a shaft opening (not illustrated) provided in the angular adjustment arm  20  and on which is mounted a pinion  14 , as illustrated in FIG. 2. The pinon  14  has pinion teeth  15  which mesh with teeth  13  provided along the edge of a crescent-shaped or semicircular angular adjustment opening  12  extending through the horizontal positioning plate  3 . Accordingly, as illustrated in FIG. 8, the angular adjustment arm  20  is capable of being positioned at selected angles “+θ” or “−θ” with respect to a longitudinal axis extending through the angular adjustment arm  20 , by rotating the angular adjustment knob  16  in the clockwise or counterclockwise direction, whereupon the pinion teeth  15  of the pinion  14  progressively mesh with the teeth  13  as the rotating pinion  14  traverses the arcuate edge of the angular adjustment opening  12  in the horizontal positioning plate  3 . Typically, the angle “+θ” and the angle “−θ” may have a value up to about 30 degrees, and the angular adjustment arm  20  can be positioned at any angle “+θ” or “−θ” typically up to about 30 degrees by rotating the angular adjustment knob  16  in the counterclockwise or clockwise direction, respectively.  
         [0024]    A support arm  22  typically angles downwardly from the extending end of the angular adjustment arm  20  and is typically welded or otherwise attached to the angular adjustment arm  20 . A vertical adjustment bracket  24  terminates the extending end of the support arm  22 , and a substantially “C”-shaped inking head  32  is friction-fitted in the vertical adjustment bracket  24 , according to the knowledge of those skilled in the art. A vertical adjustment knob  25  includes a knob shaft  26  which extends horizontally through a shaft opening (not illustrated) provided in the vertical adjustment bracket  24 . As illustrated in FIG. 4, a pinion  27  having multiple pinion teeth  28  is mounted on the knob shaft  26 , and the pinion teeth  28  mesh with rack teeth  30  of a vertical adjustment rack  29  provided along a vertical edge of the inking head  32 . Accordingly, up or down sliding vertical adjustment of the inking head  32  through the vertical adjustment bracket  24  is facilitated by clockwise or counterclockwise rotation, respectively, of the vertical adjustment knob  25 , thereby causing the pinion teeth  28  to progressively mesh with the rack teeth  30  on the vertical adjustment rack  29 .  
         [0025]    The inking head  32  includes a horizontal support plate  33  which supports an ink reservoir  35 , which may be a bottle or other container that holds a supply of ink for inking defective dies  41  on a semiconductor wafer  40 , as illustrated in FIG. 8 and hereinafter further described. An inking probe  36  which communicates with the ink reservoir  35  extends downwardly through the support plate  33  for dispensing the ink from the ink reservoir  35  to the dies  41 . Controller wiring  38  extends from a controller (not shown) and may be connected to a transducer  39  which is operably connected to the ink reservoir  35  for dispensing ink from the reservoir  35  onto the defective die or dies  41  through the inking probe  36 .  
         [0026]    It is understood that any system known by those skilled in the art may be used in conjunction with the inking head  32  to dispense the ink from the ink reservoir  35 . Accordingly, the controller (not illustrated), controller wiring  38 , transducer  39 , ink reservoir  35  and inking probe  36 , as well as the components used to operably connect the transducer  39  to the ink reservoir  35  for the dispensing of ink from the ink reservoir  35  through the inking probe  36 , may be conventional, with one novel aspect of the present invention being the facility for manually adjusting the inking head  32  in vertical relationship with respect to the semiconductor wafer  40 . It is further understood that various mechanisms known by those skilled in the art, other than the rack-and-pinion arrangements heretofore described, may be used to effect horizontal adjustment of the horizontal adjusting plate  3  on the base plate  2 ; angular adjustment of the angular adjustment arm  20  with respect to the horizontal positioning plate  3 ; and vertical adjustment of the inking head  32  on the vertical adjustment bracket  24 .  
         [0027]    Referring next to FIGS.  5 - 8 , in typical application the inking apparatus  1  of the present invention is positioned on a supporting surface  44  typically adjacent to a wafer chuck or other wafer support  42  at an inking station in a semiconductor manufacturing facility. A semiconductor wafer  40 , having had multiple dies  41  previously fabricated and tested thereon, is positioned on the wafer support  42  for marking of defective dies  41  thereon by operation of the inking apparatus  1 . Accordingly, the inking head  32  of the apparatus  1  is positioned above the appropriate defective die  41  by operating the horizontal positioning knob  4  and the angular adjustment knob  16 . The horizontal positioning knob  4  is rotated in the clockwise direction to advance the inking head  32  over the wafer  40 , such as to the position illustrated in FIG. 7, or rotated in the counterclockwise direction to retract the inking head  32  back toward the edge of the wafer  40 , such as to the position illustrated in FIG. 5. The angular adjustment knob  16  is rotated in the counterclockwise direction to move the angular adjustment arm  20  and thus, the attached inking head  32 , laterally and define a selected angle “+θ” with respect to the longitudinal axis of the angular adjustment arm  20 , as illustrated in FIG. 8. Conversely, the angular adjustment knob  16  is rotated in the clockwise direction to move the angular adjustment arm  20  and attached inking head  32  to define a selected angle “−θ” with respect to the longitudinal axis of the angular adjustment arm  20 . After the horizontal adjustment knob  4  and the angular adjustment knob  16  are rotated as appropriate to locate the inking head  32  above the appropriate defective die  41  on the wafer  40 , the vertical adjustment knob  25  is rotated to lower the inking head  32  through the vertical adjustment bracket  24  and thus, facilitate contact of the inking probe  36  with the die  41 . Next, the inking controller (not illustrated) is operated to dispense ink from the ink reservoir  35  through the inking probe  36  and onto the die  41  to mark or label the die  41  as defective. After each of the defective dies  41  is inked, the inking head  32  is first raised on the vertical adjustment bracket  24  by counterclockwise rotation of the vertical adjustment knob  25  and moved to other locations on the wafer  40  to mark additional defective dies  41  thereon. This is accomplished by manual manipulation of the horizontal positioning knob  4  and the angular adjustment knob  16  in the clockwise or counterclockwise direction in the manner therefore described.  
         [0028]    While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention. It will be appreciated by those skilled in the art that the horizontal positioning knob  4  and angular adjustment knob  16  are effective in quickly and precisely positioning the inking head  32  at a defective die  41  located at any position on the wafer  40 .