Abstract:
A method and an apparatus for the non-destructive detection of defects in the interior of semiconductor material ( 2 ) are disclosed. The semiconductor material ( 2 ) has a length (L), a cross-sectional area (Q), and a side surface ( 5 ) aligned with the length (L). An ultrasonic apparatus ( 10 ) is assigned to the semiconductor material ( 2 ). Furthermore a set-up ( 9 ) for generating a relative motion between the ultrasonic apparatus ( 10 ) and along the length (L) of the side surface ( 5 ) of the semiconductor material ( 2 ) is provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a method for non-destructive detection of defects in the interior of semiconductor material. The semiconductor material has a length and a cross-sectional area. The semiconductor material thus is bulk material, from which the single discs or plates for the semiconductor products are cut. 
         [0002]    The invention also relates to an apparatus for non-destructive detection of defects in the interior of semiconductor material. The semiconductor material has a length, a cross-sectional area, and a side surface aligned with the length. 
         [0003]    The German patent application DE 10 2006 032 431 A1 discloses a method for the detection of mechanical defects in a piece of a rod consisting of semiconductor material. The semiconductor material exhibits at least one plane surface, and a thickness of 1 cm to 100 cm, measured perpendicular to this surface. In the method the plane surface of the piece of rod is scanned with at least one ultrasonic transducer, which is coupled to the plane surface of the piece of rod by a liquid coupling medium. At each point of measurement an ultrasonic pulse is directed at least on the plane surface of the piece of rod, and the echo of the ultrasonic pulse generated by the piece of rod is recorded as a function of time, so that an echo from the plane surface, an echo of a surface of the piece of rod opposite the plane surface, and possibly further echoes are detected, wherein the positions of mechanical defects in the piece of rod are detected from the further echoes. 
         [0004]    The German patent application DE 29 36 882 discloses a testing apparatus for the detection of material defects in the interior of a component. The testing apparatus is used for components under pressure in nuclear plants. The testing head is moved to the location to be tested by a remote-controlled manipulator. The entire interior of the component is not tested for defects. 
         [0005]    The U.S. Pat. No. 6,047,600 discloses a method for testing piezo-electric materials. The time-of-arrival method is used to test the homogeneity of the material. 
         [0006]    The U.S. Pat. No. 5,381,693 discloses an imaging ultrasonic apparatus, wherein an object to be tested is scanned, while the object is irradiated with ultrasound. By the focus the plane in the material which is to be tested can be set. 
         [0007]    The international patent application WO 02/40987 discloses a method and an apparatus for the acoustic, microscopic investigation of flat substrates. The substrates to be investigated are placed into a wet-environment, in which the ultrasound is coupled in. 
       SUMMARY OF THE INVENTION 
       [0008]    There is no prior art for inspecting a rod-shaped semiconductor material, of arbitrary size and shape, with an ultrasonic apparatus in such a way that information about possible defects is retrieved from the entire bulk of the semiconductor material. 
         [0009]    It is an object of the invention to provide a method by which defects in the interior of a semiconductor material can be detected reliably. Furthermore the method according to the invention shall provide an ultrasonic image of the interior of the semiconductor material. 
         [0010]    The above object is achieved by a method according to the features claim  1 . 
         [0011]    A further object of the invention is to provide an apparatus by which defects in the interior of a semiconductor material can be localized non-destructively. Furthermore the locations of the defects in the interior of the semiconductor material shall be passed to a processing machine for the later processing of the semiconductor material. 
         [0012]    The above object is achieved by an apparatus according to the features of claim  6 . 
         [0013]    It has turned out to be particularly advantageous that with the present invention the detection of defects in the interior of a rod-shaped semiconductor material is possible. The semiconductor material has a length and a cross-sectional area. 
         [0014]    In the method according to the invention an ultrasonic apparatus is provided, wherein a relative motion is generated between the ultrasonic apparatus and a side surface of the semiconductor material. Ultrasonic pulses are emitted from the ultrasonic apparatus towards the semiconductor material during the relative motion between the semiconductor material and the ultrasonic apparatus. Parallely thereto an ultrasonic echo-signal of the ultrasonic pulses from the interior of the semiconductor material is recorded in dependence on time and space, so that the defects in the interior of the semiconductor material are detected from the entire bulk of the semiconductor material. The ultrasonic pulses and the ultrasonic echo-signal are coupled to the semiconductor material by a medium. The medium for example can be a liquid. It is also conceivable for the ultrasonic pulses and the ultrasonic echo-signal to be coupled to the semiconductor material by air or some other gaseous medium. 
         [0015]    The relative motion between the ultrasonic apparatus and the semiconductor material is generated by moving the ultrasonic apparatus along the length of the semiconductor material. 
         [0016]    The semiconductor material can be of cylindrical shape. During the motion of the ultrasonic apparatus along the length of the semiconductor material at least one sector up to the centre of the semiconductor material is captured. The cylindrical semiconductor material is rotated about an axis in order to capture the subsequent at least one sector up to the centre of the semiconductor material. This is continued until the entire bulk of the semiconductor material has been captured and represented as an image. 
         [0017]    Furthermore a computer control is provided, by which the ultrasonic echo-signals returning from the interior of the semiconductor material are handled in such a way that ultrasonic echo-signals from the region of the at least one sector are processed, and that the ultrasonic echo-signals from outside the sector are not processed for the imaging. 
         [0018]    Furthermore it is possible to investigate a semiconductor material of cuboid shape by the method according to the invention. Here, too, during the motion of the ultrasonic apparatus along the length of a first outer surface of the semiconductor material at least one cuboid up to a central plane of the semiconductor material is captured. The ultrasonic apparatus is displaced transversely to the length of the semiconductor material, so that during the subsequent movement of the ultrasonic apparatus along the length of the first outer surface of the semiconductor material at least one cuboid up to the central plane of the semiconductor material is captured, and that, after all the cuboids from the first surface to the central surface have been captured, the semiconductor material is turned by 180° to capture further cuboids from the second outer surface. 
         [0019]    Here, too, a computer control is provided, by which the ultrasonic echo-signals returning from the interior of the semiconductor material are handled in such a way that ultrasonic echo-signals from the region of the at least one cuboid up to the central surface are processed, and the ultrasonic echo-signals outside the at least one cuboid are not processed. 
         [0020]    The apparatus for the non-destructive detection of defects in the interior of the semiconductor material comprises an ultrasonic apparatus assigned to the semiconductor material. Furthermore a set-up for generating a relative motion between the ultrasonic apparatus along the length of the side surface of the semiconductor material is provided. 
         [0021]    The ultrasonic apparatus may comprise plural transducers, located at a distance from the side surface. The ultrasonic pulses emitted from the transducers are coupled into the semiconductor material by a medium. To this end liquid or gaseous media are conceivable. Depending on the medium used the transducers need to be designed accordingly with respect to their power. 
         [0022]    According to an embodiment of the invention the plural transducers are arranged in a row at equal distances. A further embodiment consists in the transducers being arranged at equal distances in a matrix. 
         [0023]    The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Subsequently embodiments shall illustrate the method according to the invention and the apparatus according to the invention and their advantages with reference to the accompanying figures. 
           [0025]      FIG. 1  shows a schematic view of the apparatus for the non-destructive detection of defects in the interior of cylindrical semiconductor material. 
           [0026]      FIG. 2  shows a schematic view of an apparatus for the non-destructive detection of defects in the interior of cuboid semiconductor material. 
           [0027]      FIG. 3  shows a top view of the circular cross-sectional area and the corresponding linear ultrasonic apparatus. 
           [0028]      FIG. 4  shows a top view of the circular cross-sectional area and the corresponding matrix-like ultrasonic apparatus. 
           [0029]      FIG. 5  shows a top view of the rectangular cross-sectional area and the corresponding linear ultrasonic apparatus. 
           [0030]      FIG. 6  shows a top view of the rectangular cross-sectional area and the corresponding matrix-like ultrasonic apparatus. 
           [0031]      FIG. 7  shows a possible embodiment of the linear arrangement of the individual transducers with respect to the side surface of the semiconductor material. 
           [0032]      FIG. 8  shows a possible embodiment of the matrix-like arrangement of the individual transducers with respect to the side surface of the semiconductor material. 
       
    
    
       [0033]    For like elements of the invention or elements of like function identical reference numerals are used. Furthermore only those reference numerals are used in the individual figures which are necessary for the description of the respective figure. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]      FIG. 1  shows a schematic view of the apparatus  1  for the non-destructive detection of defects in the interior of cylindrical semiconductor material  2 . With the apparatus  1  according to the invention semiconductor materials  2  of arbitrary cross-section Q can be investigated. In the embodiment shown in  FIG. 1  the semiconductor material  2  has a circular cross-section Q. The shapes of the cross sections shown here are not to be taken by way of limitation of the invention. It is possible to investigate the rod-shaped semiconductor material  2  of arbitrary cross-sections with the apparatus  1  according to the invention. 
         [0035]    The semiconductor material  2  to be investigated therein is placed in a container  6  filled with a liquid  8 . The ultrasonic apparatus  10  comprises plural transducers  12 , from which the emitted ultrasonic pulses are coupled to the semiconductor material  1  via the liquid  8 . Though in the figures a liquid is shown as the medium used, this is not to be taken as a limitation of the invention. It is also conceivable that the ultrasonic pulses and the ultrasonic echo-signal are coupled to the semiconductor material via air or some other gaseous medium. The coupling via air is not shown in the figures, it is obvious to a person skilled in the art how to design the transducers with respect to power so that the coupling via air yields satisfactory results with respect to the defects in the interior of the semiconductor material  1 . According to the double arrow  9  shown in  FIG. 1  the ultrasonic apparatus  10  can be moved relative to the semiconductor material  2  along its length L. A control and evaluation device  14  is provided. The control and evaluation device  14  thus also serves for the control of the relative motion between the ultrasonic apparatus  10  and the semiconductor material  2 , for the control of the emission of ultrasonic pulses onto the semiconductor material  2  and parallely thereto also for recording the ultrasonic echo-signal from the interior of the semiconductor material  2 . The relative motion is along the length L of the semiconductor material  2 . In order to capture the entire bulk of the semiconductor material  2  with the apparatus  1  according to the invention, the semiconductor material  2  is mounted so that it may be rotated about an axis  4 . The direction of rotation of the rod-shaped semiconductor material  2  is indicated in  FIG. 1  by the arrow  4   a . The ultrasonic apparatus  10  is located opposite the side surface  5  of the semiconductor material  2 . 
         [0036]      FIG. 2  shows a schematic view of the apparatus  1  for the non-destructive detection of defects in the interior of cuboid semiconductor material  2 . Here the ultrasonic apparatus  10  at first is located opposite a first surface  5   a  of the side surface  5  of the semiconductor material  2 . First the first surface  5   a  of the side surface  5  of the semiconductor material  2  is scanned with the ultrasonic apparatus  10 . Thus the interior of the semiconductor material  2  up to a central plane  3  is captured with the ultrasonic apparatus  10 . After capturing this part of the semiconductor material  2 , the semiconductor material  2  is turned by 180°, and the second surface  5   b , which is opposite the first surface  5   a , is scanned. In this way the second part of the bulk of the semiconductor material  2  is captured. 
         [0037]      FIG. 3  shows a top view of the circular cross-sectional area  20  and of the linear ultrasonic apparatus  10 . The at least one transducer  12  of the ultrasonic apparatus  10  therein is located in such a way that it is opposite a line (see  FIG. 7 ) of the side surface  5 . The ultrasonic apparatus  10  and the control and evaluation device  14  therein cooperate in such a way that a sector of a circle  21  up to the centre M of the semiconductor material  2  is captured of the semiconductor material  2 . The sector of a circle  21  extends along the length L of the semiconductor material  2 . Once a sector of a circle  21  has been captured, the semiconductor material  2  is rotated about the axis  4  and the subsequent sector of a circle  21  is captured with the ultrasonic apparatus  10 . 
         [0038]      FIG. 4  shows a top view of the circular cross-sectional area  20  and the linear ultrasonic apparatus  10 . The ultrasonic apparatus  10  comprises plural transducers  12  arranged in a matrix. The representation in  FIG. 4  shows the first row of the matrix. Therein the transducers  12  are located in such a way with respect to the semiconductor material  2  that each transducer exhibits the same distance from the side surface  5  of the semiconductor material  2 . The ultrasonic apparatus  10  and the control and evaluation device  14  therein cooperate in such a way that a sector of a circle  21  up to the centre M of the semiconductor material  2  is captured of the semiconductor material  2 . The sector of a circle  21  extends along the length L of the semiconductor material  2 . Once a sector of a circle  21  has been captured, the semiconductor material  2  is rotated about the axis  4  and the subsequent sector of a circle  21  is captured with the ultrasonic apparatus  10 . The sector of a circle  21  captured with the matrix arrangement is larger than the sector of a circle captured with the linear arrangement of plural transducers  12 . 
         [0039]      FIG. 5  shows a top view of the rectangular cross-sectional area  30  and the linear ultrasonic apparatus  10 . The at least one transducer  12  of the ultrasonic apparatus  10  therein is arranged in such a way that it is located opposite a part of the first surface  5   a  of the side surface  5 . The ultrasonic apparatus  10  and the control and evaluation device  14  (see  FIG. 1 ) therein cooperate in such a way that a cuboid  31  up to the central plane  3  of the semiconductor material  2  is captured of the semiconductor material  2 . The cuboid  31  extends along a length L of the semiconductor material  2 . Once a cuboid  31  has been captured, the ultrasonic apparatus  10  is displaced (in direction of the arrow  32 ), so that the next cuboid can be captured with the ultrasonic apparatus  10 . Once all cuboids  31  from the first surface  5   a  to the central plane  3   a  have been captured, the semiconductor material  2  is turned by 180°. Then the plurality of cuboids  31  from the second surface  5   b  of the side surface  5  to the central plane  3  are captured. In this way it is possible to capture the entire bulk of the semiconductor material  2  with a rectangular cross section  30 . Though the description is limited to a rectangular shape, this is not to be taken as a limitation of the invention. The cross section can have the shape of a square also, or deviate somewhat from the rectangular or square shape. 
         [0040]      FIG. 6  shows a top view of the rectangular cross-sectional area  30  and the matrix-like ultrasonic apparatus  10  for capturing the entire bulk of the semiconductor material  2 . The difference to the embodiment shown in  FIG. 5  is that a larger cuboid  31  can be captured with the matrix arrangement of the transducers  12  than with the arrangement of  FIG. 5 . The individual transducers  12  of the matrix arrangement therein are essentially arranged parallel to the first surface  5   a  or the second surface  5   b , respectively. 
         [0041]      FIG. 7  shows a possible embodiment of the linear arrangement of the individual transducers  12  with respect to the side surface  5  of the semiconductor material  2 . In the embodiment shown here for example the first surface  5   a  of the semiconductor material  2  is scanned with the linear arrangement (row arrangement  50 ) of the transducers  12 . The individual transducers  12  are located at an equal distance  40  from each other along the length L of the semiconductor material. For capturing a cuboid  31  of the interior of the semiconductor material  2  up to the central plane  3  (see  FIG. 5 ) the row arrangement  50  is displaced by the value of the distance  40 . In this way at least a part of the bulk of the semiconductor material  2  is captured within a relatively short time. For the next section of the bulk of the semiconductor material  2  to be captured the row arrangement  50  of the transducers  12  is displaced perpendicular to the length L of the semiconductor material  2 . Afterwards again a displacement of the row arrangement  50  by the value of the distance  40  follows. This is continued until the entire first surface  5   a  has been scanned and the corresponding bulk of the semiconductor material  2  has been captured. 
         [0042]      FIG. 8  shows a possible embodiment of the matrix-like arrangement of the individual transducers  12  with respect to the first surface  5   a  of the side surface  5  of the semiconductor material  4 . The entire matrix  55  of the transducers  12  is displaced according to the sequence shown in  FIG. 7 . It is self-evident that a larger region of the bulk of the semiconductor material  2  can be captured with the matrix  55  than with the embodiment shown in  FIG. 7 . In the case of a matrix arrangement the signal-processing effort for the ultrasonic echo-signal returning from the interior of the semiconductor material  2  is higher. 
         [0043]    The invention has been described with reference to a preferred embodiment. It is obvious for a person skilled in the art, however, that alterations or modifications of the invention can be made without leaving the scope of the subsequent claims.