Abstract:
The invention is a method for detecting float or peel of semiconductor chips arranged in X and Y axes directions diced and bonded to a dicing tape on a stage. The method includes detecting float or peel of the semiconductor chips in a respective horizontal or longitudinal row arranged in the X or Y axis direction; moving the stage in the X axis direction, the Y axis direction, a Z axis direction, and a rotational direction around the Z axis for aligning the stage with a position detection unit for detecting positions of the semiconductor chips in the X axis direction and the Y axis direction; detecting the positions of abnormal semiconductor chips in the respective horizontal or longitudinal row that includes said abnormal semiconductor chips; and specifying the positions of said abnormal semiconductor chips on the X-Y axes.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority of Japanese Patent Application Number 2004-031868, filed on Feb. 9, 2004. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a chip mis-position detection method for detecting a mis-position of a semiconductor chip on a dicing tape when an electrical characteristic inspection, of the semiconductor chips fixed to the dicing tape, is carried out. 
   2. Description of the Related Art 
   A large number of semiconductor devices (chips), forming the same electrical chip circuits, are formed on a surface of a wafer, and an approval/rejection judgment is made by using a prober to inspect electrical characteristics of each electrical chip circuit before the wafer is diced into discrete semiconductor devices (semiconductor chips). The prober generally has a construction in which a probe card having a probe corresponding to each semiconductor device of the wafer and connected to a tester is allowed to serially correspond to each semiconductor chip, brings its probes into contact with electrode pads of the semiconductor device and conducts electric measurement. 
   To reduce size, weight and thickness of electronic appliances such as cellular telephone units, digital cameras and mobile information terminals, a packaging technology for semiconductor integrated circuitry has now reached the stage of a chip size package (CSP) or a wafer level chip size package (WCSP). The CSP uses semiconductor chips arranged in a stack. 
   Therefore, a wafer having a reduced thickness of 100 μm or below has been required. In such thin wafers, the possibility of defect has become high during the process in which the wafer is diced into discrete semiconductor chips in a dicing step after the electrical characteristic test by using a prober. The demand is also high that the electrical characteristic test be conducted as much as possible in the last stage of the production of the semiconductor chips to reduce the percentage of defectives in the packaged products. 
   The electrical characteristic test of the semiconductor chips in the chip state has been made in the past by using a frame-carrying prober. In this case, to prevent the semiconductor chips diced during the dicing step from scattering, a dicing tape is bonded to a surface of the wafer on which the electronic chip circuits are not formed, and the wafer is then diced. The dicing tape has a round shape the same as the wafer and after the wafer is diced, the dicing tape is stretched in such a manner as to increase its diameter and is held under the stretched state by a ring-like metal frame. In other words, the discrete semiconductor chips diced are held as bonded to the dicing tape while the gaps (breaks) between the semiconductor chips are somewhat expanded. The semiconductor chips are carried under such a state by the frame and the electrical characteristic test of the discrete semiconductor chips is conducted while the semiconductor chips are held on the stage of the frame-carrying prober. 
   According to the prior art method described above, however, some semiconductor chips peel from the dicing tape from time to time. When the electrical characteristic test is started under this state, the semiconductor chips that are about to peel come into contact with probes of a probe card of the frame-carrying prober and breaks the probes and the chips. When alignment is conducted to position the semiconductor chips, the peeling semiconductor chips impinge against an alignment camera and break the alignment camera and the semiconductor chips. 
   SUMMARY OF THE INVENTION 
   In view of the problems described above, the invention provides a chip mis-position detection method that detects beforehand semiconductor chips peeling or floating from a dicing tape, and can prevent breakage of semiconductor chips, probe card probes, alignment camera, etc, by specifying the peel positions. 
   The mis-position detection method of chips according to the present invention includes first detection means disposed on the side of a frame-carrying prober, for detecting float peel of semiconductor chips inside a horizontal or longitudinal row unit regularly arranged in an X or Y axis direction and second detection means disposed above the stage of the frame-carrying prober, for detecting the positions of abnormal semiconductor chips in a horizontal or longitudinal unit row including the abnormal semiconductor chips float or peel of which is detected by the first detection means, and specifies the positions of the abnormal semiconductor chips, float or peel of which is detected, on the X-Y coordinate axes among a large number of semiconductor chips regulated arranged in the X and Y axes directions by using the first and second detection means while the stage is being moved in the X and Y axes directions. Therefore, the invention can detect in advance the semiconductor chips peeling or floating from the dicing tape, can thus specify their positions and can, in advance, remove such abnormal semiconductor chips, so that the invention can prevent breakage of the probe card probes, the alignment camera and the semiconductor chips resulting from the contact with the abnormal semiconductor chips. 
   In the chip mis-detection method according to the present invention, the first and second detection means utilize a laser beam. 
   A defective electrode pad detection method according to the present invention detects defective electrode pads in each semiconductor device set onto a prober by utilizing the mis-position detection method of chips described above, and can prevent the occurrence of defects such as bending of probes due to the defective electrode pads and breakage of a probe card. 
   The invention will become more apparent from the following description of embodiments thereof when taken in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  schematically shows an overall construction of a frame-carrying prober to which a chip mis-position detection method of an embodiment of the invention is applied; 
       FIG. 2  is a side view useful for explaining the chip mis-position detection method of the invention; and 
       FIG. 3  is a plan view useful for explaining the chip mis-position detection method of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A frame-carrying prober according to an embodiment of the invention will be hereinafter explained with reference to the accompanying drawings. An ordinary prober and a frame-carrying prober are different only in that the prober inspects electrical characteristics of semiconductor devices formed on a wafer whereas the frame-carrying prober inspects the electrical characteristics of semiconductor chips diced discretely from the wafer as described above, and they have a similar mechanism.  FIG. 1  schematically shows an overall construction of the frame-carrying prober according to the invention.  FIG. 2  explains mis-position detection means having first and second detection means as the feature of the invention. 
   The frame-carrying prober  1  include a stage  2 , a stage driving motor  3 , a probe card  4  equipped with probes  41 , a tester  5 , an alignment optical device  6 , a CCD camera  7  on the stage side and a control portion  8  in the same way as the ordinary prober. The frame-carrying prober  1  further includes mis-position detection means having first and second detection means  9 A and  9 B. 
   Discrete semiconductor chips  10  diced from a wafer are held by a ring-like frame  12  while they are bonded onto a dicing tape  11  and are carried under this state. To form the semiconductor chips  10  under this state, the dicing tape  11  is bonded to the back of the wafer on which electrical chip circuits are not formed, and the wafer is then diced. When dicing is done in this way, the discrete semiconductor chips  10  are bonded to the dicing tape  11  as diced. Next, the dicing tape  11  is uniformly stretched in a radial direction and is held as stretched by the ring-like frame  12 . The semiconductor chips  10  are carried under this state by the frame  12 . 
   The semiconductor chips  10  are put on and held by a chuck portion  21  on the state together with the frame  12 . The stage  2  is so constituted as to be capable of moving in X, Y and Z directions and in a θ rotating direction with the Z axis as the center by a stage driving motor  3  controlled by the control portion  8 . The stage  2  can three-dimensionally move the semiconductor chips  10  held by the chuck portion  21  of the stage  2 . 
   A large number of electrode pads (not shown in the drawings) are formed on the surface of the semiconductor chips  10  and the probe card  4  is provided with probes  41  corresponding to the electrode pads of the semiconductor chips  10 . Therefore, the electrical characteristics of the semiconductor chips  10  can be inspected by bringing the probes  41  of the probe card  4  connected to the tester  5  into contact with the electrode pads of the semiconductor chips  10 . Incidentally, when a plurality of semiconductor chips  10  is inspected at once, the probe card  4  has the same number of probes  41  as the number of the electrode pads. 
   The frame-carrying prober  1  according to the invention includes the alignment optical device  6  using an alignment camera for positioning the probes  41  of the probe card  4  with the electrode pads of the semiconductor chip  10  in the same way as the ordinary prober. In other words, the CCD camera  7  for imaging from below the probes  41  and detecting the distal end positions of the probes  41  is fitted to the stage  2 . The CCD camera  7  is moved when the stage  2  is operated, measures the distal end position of each probe  41  while establishing its focus and inputs the measurement result to the control portion  8 . The alignment optical device  6  recognizes the pattern of the semiconductor chips  10  and inputs the recognition result to the control portion  8 . In this way, the control portion  8  can automatically conduct positioning between the distal end of each probe  41  and each electrode pad of the semiconductor chip  10  by using a known image processing technology on the basis of the information acquired by the alignment optical device  6  and the positional information of the distal end of each probe  41  acquired by the CCD camera  7  of the stage  2 . 
   The frame-carrying prober  1  according to the invention further includes the mis-position detection means  9  having the first and second detection means  9 A and  9 B for detecting the semiconductor chips  10  peeling or floating from the dicing tape  11  as the feature of the invention. The first detection means  9 A of the mis-position detection means  9  includes a light emission portion  91  for emitting a laser beam L, a light reception portion  92  for receiving the laser beam L from the light emission portion  91 , a judgment portion  93  for judging peel or float of the semiconductor chips  10  from the laser beam L received by the light reception portion  92  depending on the increase/decrease of the light reception amount and an amplification portion  94 . The laser beam L emitted from the light emission portion  91  is turned to parallel rays by a lens  95  and travels on the semiconductor chips  10  towards the light reception portion  92 . When some of the semiconductor chips peel from the dicing tape  11  and partially float up, a part of the leaser beam L is cut off by these semiconductor chips  10   a  and does not reach the light reception portion  92 . As the laser beam L is emitted above the semiconductor chips  10  and is gradually brought close to the upper surfaces of the semiconductor chips  10  by, for example, moving the stage  2  in the Z axis direction, the semiconductor chip or chips  10   a  peeling or floating from the dicing tape  11  in the horizontal row or the longitudinal low parallel to the X or Y axis can be detected from the increase/decrease of the light reception amount in the light reception portion  92 . 
   In this case, when the light emission portion  91  and the light reception portion  92  as the first detection means  9 A are arranged in the X axis direction as shown in  FIG. 3 , peel or float of the semiconductor chips  10  inside the entire horizontal row parallel to the X axis can be detected by moving the stage  2  in the Y axis direction. Incidentally, when the light emission portion  91  and the light reception portion  92  as the first detection means  9 A are arranged in the Y axis direction, peel or float of the semiconductor chips  10  inside the entire longitudinal row parallel to the Y axis can be detected by moving the stage  2  in the X axis direction. Even though peel or float of the semiconductor chips  10   a  inside the horizontal row or the longitudinal row can be detected by the first detection means  9 A alone, however, it is not possible to specify the semiconductor chip or chips  10   a  of which of the horizontal and longitudinal rows peel or float. In other words, it is not possible to correctly detect the existence of peel or float of the discrete semiconductor chips  10  on the X-Y coordinate axes. 
   Therefore, the invention includes the second detection means  9 B as the mis-position detection means  9 . This second detection means  9 B is arranged above the stage  2  and includes a light emission portion (not shown) for emitting the laser beam M and a light reception portion (not shown) for receiving the reflected laser beam M and is connected to a judgment portion  93  for judging peel or float from the concavo-convex condition of the semiconductor chips  10  and to an amplification portion  94 . The first detection means  9 A judges peel or float of the semiconductor chips  10  by the increase/decrease of the light reception amount of the laser beam L but the second detection means  9 B judges peel or float of the semiconductor chips  10  from their concavo-convex condition due to the change with time from light emission to light reception. 
   In other words, when the first detection means  9 A judges that peel or float of the semiconductor chip(s)  10   a  exists in a specific horizontal row parallel to the X axis, for example, the stage  2  is moved in the Y axis direction in such a fashion that this specific horizontal row is situated just below the second detection means  9 B. The stage  2  is moved in the X axis direction under this condition and the position of the semiconductor chip  10   a  in the specific horizontal row that peels or float is specified. 
   When the first detection means  9 A is arranged in the Y axis direction and peel or float of the semiconductor chip  10   a  is detected in a specific longitudinal direction parallel to the Y axis, too, the position of the semiconductor chip  10   a  in the specific longitudinal row that peels or floats can be specified by the same method as described above. 
   The invention can thus specify the position of the semiconductor chip  10   a,  that peels or floats, on the X-Y coordinates by using the first detection means  9 A and the second detection means  9 B as the peel detection means  9 . 
   The semiconductor chip  10   a  which is judged as defective by the judgment portion  93  and the position of which is specified is removed either manually or automatically. Alternatively, the electrical characteristic test is carried out in such a fashion as to avoid the defective semiconductor chips  10   a . In this way, contact of the peeling or floating semiconductor chip with the probe card probe or with the alignment camera can be avoided and their breakage can be prevented. 
   The invention is suitable particularly when a space for installing the detection means is available in only one of the X and Y axes directions or on only one of the sides but a space for installing the detection means above the stage is available. 
   The embodiment described above uses the laser beams L and M and detects peel or jump-out of the semiconductor chips  10  from the dicing tape  11  but may use ultrasonic wave in place of the laser beams L and M. Quite naturally, a transmission portion of the ultrasonic wave and a reception portion of the ultrasonic wave are used in this case in place of the light emission portion  91  of the laser beam and the light reception portion of the laser beam, respectively. 
   The embodiment described above detects the semiconductor chips  10  peeling or floating from the dicing tape  11  but can also detect defective electrode pads among those formed on each semiconductor device of the wafer set onto the probe by utilizing the same principle. In other words, the electrode pads such as bump pads are formed on the semiconductor device but some electrode pads are formed, in some cases, to a height greater than that of the normal electrode pads. When the probes of the probe card come into contact with such defective electrode pads, abnormal force acts on the probes, so that the probes are bent or broken and this results in breakage of the probe card. It is therefore necessary to determine in advance the coordinate positions of the defective electrode pads, to avoid probing and to prevent breakage of the probe card. The positions of the defective electrode pads on the wafer can be detected by using the first and second detection means according to the invention. 
   Although the invention has thus been described about the specific embodiments thereof, it will be obvious to those skilled in the art that numerous changes or modifications can be made thereto without departing from the scope of claim and concept of the invention.