Abstract:
The present invention provides a cleaning apparatus capable of removing foreign matters attached to a tip of a probe effectively without impairing the durability of the probe. The cleaning apparatus for the probe comprises a base plate having a rough surface and a surface layer formed to conform to and cover the rough surface for the purpose of providing a polishing surface for the probe and having lower hardness than hardness of the probe tip of the probe.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a cleaning apparatus for removing foreign matters from a probe tip of a probe card used in an electrical test of a semi conductor device such as an integrated circuit formed on a semiconductor wafer. 
         [0002]    In an electrical test of semiconductor devices collectively formed on a semiconductor wafer, an electrical connecting apparatus such as a probe card connected to a tester is used in general to connect the tester used in the test to a device under test. The tip of each probe provided on this electrical connecting apparatus contacts an electrode pad formed on each semiconductor device of the semiconductor wafer to cause the semiconductor device as a device under test to be electrically connected to the aforementioned tester. 
         [0003]    At the time of the mutual connection, the tip of the probe of the electrical connecting apparatus slides on the surface of the corresponding electrode pad and abuts on this electrode pad so as to slightly scrape the surface of the electrode pad so that the probe can be connected to the corresponding electrode pad reliably. At this time, scrapes of the electrode pad may attach to the tip of the probe as foreign matters. Since attachment of such foreign matters to the probe tip interferes with subsequent accurate electrical connection for other semiconductor devices, it interferes with accurate tests. 
         [0004]    It is proposed that a cleaning member having an elastic layer containing polishing agent on the rough surface of a base plate is used to remove foreign matters attached to the probe tip (for example, refer to Patent Document 1). According to this cleaning member, by letting the probe tip slide on the elastic layer of the cleaning member as needed, the foreign matters attached to the probe can be removed. 
         [0005]    [Patent Document 1] Japanese Patent No. 3766065 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    However, since the elastic layer contains the polishing agent having higher hardness than hardness of the probe, the tip of the probe significantly abrades away per cleaning of the probe. Thus, the durability of the probe may be impaired. 
         [0007]    It is an object of the present invention to provide a cleaning apparatus enabling to remove foreign matters attached to a tip of a probe effectively without impairing the durability of the probe. 
         [0008]    The present invention is a cleaning apparatus for removing foreign matters attached to a probe, and comprises a base plate having a rough surface, and a surface layer formed to conform to and cover the rough surface for the purpose of providing a polishing surface for the probe and having lower hardness than hardness of a probe tip of the probe. 
         [0009]    The surface layer is lower in hardness than the probe and is formed on the rough surface to conform to the base plate. Accordingly, by letting the probe tip of the probe slide on the surface layer, foreign matters attached to the probe can be removed effectively without causing significant abrasion of the probe. 
         [0010]    The surface layer may be formed to have a smooth surface along the rough surface. 
         [0011]    The thickness of the surface layer may be 0.05 to 1.0 micrometers. 
         [0012]    The arithmetic mean roughness (Ra) of the rough surface may be 0.02 to 1.00 micrometers. In this case, the arithmetic mean roughness (Ra) value of the rough surface of the surface layer is approximately 10% smaller than the arithmetic mean roughness value of the rough surface of the base plate. 
         [0013]    For the base plate, a silicon plate whose surface is formed to be a rough surface by sandblast may be used, for example. As the base plate, an amorphous carbon plate, a silicon carbide plate, or a ceramic plate can be used instead of the silicon plate. 
         [0014]    When the Vickers hardness (Hv) of the probe tip of the probe is 800 to 1000, a metal material having the Vickers hardness (Hv) of 400 to 600 may be used for the surface layer. 
         [0015]    For example, in a case where a hard metal such as rhodium or ruthenium is used as the probe tip, nickel or a nickel alloy may be used for the metal material of the surface layer. The surface layer can be formed by deposition of copper, a copper alloy, tungsten, a tungsten alloy, chromium, or a chromium alloy, instead of the nickel material. 
         [0016]    With the present invention, since foreign matters such as aluminum scraps attached to the probe tip can be removed without using a conventional surface layer containing polishing agent as described above, the tip of the probe will not abrade away as significantly as in the conventional case in cleaning of the probe. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0017]      FIG. 1  is a cross-sectional view schematically showing a cleaning apparatus according to the present invention. 
           [0018]      FIG. 2  is a schematic view partially showing a probe assembly that undergoes cleaning by using the cleaning apparatus shown in  FIG. 1 . 
           [0019]      FIG. 3  is a front view of a probe in the probe assembly shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]      FIG. 1  is a cross-sectional view schematically showing a cleaning apparatus according to the present invention. Prior to description of the cleaning apparatus shown in  FIG. 1 , an example of a probe assembly having a probe that undergoes cleaning processing by the cleaning apparatus will be described with reference to  FIGS. 2 and 3 . 
         [0021]    A probe assembly  10  according to the present invention is used for an electrical test of a plurality of integrated circuits (not shown) formed on a semiconductor wafer  12  as shown in  FIG. 2 . The semiconductor wafer  12  is removably held on a vacuum chuck  14 , for example, with a plurality of electrodes  12   a  formed on its one surface directing upward. The probe assembly  10  is supported by a not shown frame member to be movable relatively to the vacuum chuck  14  in directions toward and away from the semiconductor wafer  12  on the vacuum chuck  14  for the electrical test of the aforementioned integrated circuits of the semiconductor wafer  12  on the vacuum chuck  14 . 
         [0022]    The probe assembly  10  comprises a printed wiring board  16  and a probe board  18  piled up on the printed wiring board. The probe board  18  is a layered body made of a ceramic board  18   a  and a multi-layered wiring board  18   b  whose upper surface is connected to the ceramic board, as is conventionally well known. On the lower surface of the probe board  18 , that is, the multi-layered wiring board  18   b , are aligned and mounted a plurality of probes  20  according to the present invention. 
         [0023]    The probe board  18  is attached integrally with the printed wiring board  16  so as to be piled on the lower surface of the printed wiring board  16  via a conventionally well-known attachment ring assembly  22  made of a dielectric material such as a ceramic and not shown combining members similar to conventional ones such as bolts so that the probes  20  may be directed downward. In the example shown in the figure, on the upper surface of the printed wiring board  16  is integrally arranged a reinforcement member  24  that is made of a metal material and allows partial exposure of the aforementioned upper surface of the printed wiring board  16 . 
         [0024]    On the multi-layered wiring board  18   b  of the probe board  18  are formed conventionally well-known plural conductive paths  26  as shown in  FIG. 3 . The respective probes  20  are attached to the probe board  18  by being fixedly connected to probe lands  26   a  of the respective corresponding conductive paths  26 . 
         [0025]    The aforementioned conductive paths on the probe board  18  corresponding to the respective probes  20  are electrically connected to sockets (not shown) arranged in an area exposed from the reinforcement member  24  on the upper surface of the printed wiring board  16  via respective conductive paths (not shown) respectively penetrating the ceramic board  18   a  and the printed wiring board  16  as in a conventionally well-known manner and are connected to a circuit of a not shown tester main body via the sockets. 
         [0026]    Accordingly, by letting the probe assembly  10  and the vacuum chuck  14  move so as to approach each other so that the respective probes  20  of the probe assembly  10  may abut on the corresponding electrodes  12   a  on the semiconductor wafer  12  as a device under test, the electrodes  12   a  can be connected to the circuit of the aforementioned tester main body, and thus an electrical test of the device under test  12  can be performed. 
         [0027]    Referring to  FIG. 3 , which is an enlarged view of each probe  20 , each probe  20  comprises a plate-shaped probe main body  20   a  and a probe tip  20   b  part of which is buried in the probe main body. They exhibit relatively good conductivity. 
         [0028]    The probe main body  20   a  may be made of a highly flexible metal material with relatively excellent flexibility such as nickel, a nickel alloy including a nickel-phosphorus alloy, a nickel-tungsten alloy, a nickel-cobalt alloy, and a nickel-chromium alloy, or phosphor bronze. Also, the probe tip  20   b  is made of a metal material whose Vickers hardness (Hv) is 800 to 1000 such as rhodium or ruthenium. The probe tip  20   b  made of such a metal material is higher in hardness and more excellent in abrasion resistance than the probe main body  20   a.    
         [0029]    In the example shown in the figure, the probe main body  20   a  comprises an attachment region  28  whose flat surface shape is a rectangular shape, a strip-shaped connection region  30  extending downward from one side of the attachment region, arm regions  32 ,  32  extending in a lateral direction from the connection region, and a probe tip region  34  continuing into the arm regions. An upper edge  28   a  of the attachment region  28  is an attachment end portion to the probe land  26   a . In the example shown in the figure, the arm regions  32  continue into the attachment region  28  extending downward from the upper edge or the attachment end portion  28   a  via the connection region  30 . 
         [0030]    The arm regions  32  extend in a lateral direction with a space from a lower edge  28   b  of the attachment region  28 . In the example shown in the figure, the arm regions  32  are a pair of arm regions  32 ,  32  extending in parallel with each other at a distance from each other in an up-down direction. The probe tip region  34  extends from the tip ends of both the arm regions to the opposite side of a side where the attachment end portion  28   a  is located, that is, to the lower side, so as to connect both the arm regions  32 . 
         [0031]    Each probe  20  is fixed to the probe land  26   a  of the conductive path  26  at the attachment end portion  28   a  of the probe main body  20   a , and as shown in  FIG. 2 , the plurality of probes  20  are arranged in series to be close to one another with their probe tips  20   b  aligned on a straight line. 
         [0032]    According to the probe assembly  10 , when the probe tip  20   b  of the probe  20  abuts on the electrode  12   a  of the aforementioned semiconductor wafer  12 , the probe assembly  10  further receives an action force in a direction in which the semiconductor wafer  12  and the probe assembly  10  approach each other. Due to this action force, arc-like retroflexion opened upward occurs in the arm regions  32 ,  32  of the probe assembly  10  by the elasticity. This action force causing the retroflexion is generally referred to as an overdriving force. The probe tip  20   b  of each probe  20  slightly slides on the electrode  12   a  by the overdriving force and scrapes the surface of the electrode  12   a  by this slide. Generally, since the surface of the electrode  12   a  is covered with oxide (electrical insulating substance) of the electrode, non-conductivity may occur, and it is thought that reliable electrical contact can be attained by scraping of the surface. 
         [0033]    However, when scrapes of the electrode  12   a  occurring at this time attach to the probe tip  20   b , these attachments cause a failure such as non-conductivity by residing between the probe tip  20   b  and the electrode  12   a  at the time of subsequent tests of other integrated circuit areas of the semiconductor wafer  12  or another semiconductor wafer  12 . 
         [0034]    Under such circumstances, the cleaning apparatus according to the present invention shown in  FIG. 1  is used for removal of foreign matters attached to the probe tip  20   b  of the probe  20 . 
         [0035]    The cleaning apparatus  40  according to the present invention comprises a base plate  42  and a surface layer  44  formed on the base plate as shown in  FIG. 1 . As the base plate  42 , a silicon plate such as a silicon crystal substrate can be used. A surface  42   a  of the base plate  42  undergoes miltor processing by e.g., surface polishing as needed and thereafter is processed to become a rough surface by e.g., sandblast processing. 
         [0036]    By this surface roughening, the surface  42   a  of the base plate  42  is formed so that the arithmetic mean roughness (Ra) may become 0.02 to 1.00 micrometers. 
         [0037]    On the surface  42   a  of the base plate  42  that has undergone the surface roughening, the surface layer  44  is formed. This surface layer  44  is made of a metal material whose Vickers hardness (Hv) value is 400 to 600, which is smaller than that of the probe tip  20   b . Such a metal material is represented by nickel or a nickel alloy. 
         [0038]    This metal material for the surface layer  44  is deposited on the surface  42   a  to have a thickness of 0.05 to 1.0 micrometers by using, e.g., a spattering technique. By this deposition of the metal material, the surface layer  44  having a surface  44   a  approximately conforming to convexo-concave of the surface  42   a  of the base plate  42  is formed. This surface  44   a  of the surface layer  44  forms a smoother curve surfaced than the surface  42   a  of the base plate  42  does, and the arithmetic mean roughness (Ra) value of the surface  44   a  of the surface layer  44  is approximately 10% smaller than the arithmetic mean roughness value of the surface  42   a  of the base plate  42 . Also, although convexo-concave corresponding to the corners of the convexo-concave of the surface  42   a  of the base plate  42  is formed on the surface  44   a  of the surface layer  44  in the schematic view of  FIG. 1 , the surface  44   a  with these corners is in fact a smooth curved surface. Thus, even in a case where corners are formed on the surface  42   a  of the base plate  42 , no corner-like parts occur on the surface  44   a  of the surface layer  44 . The surface layer  44  of the cleaning apparatus  40  according to the present invention does not contain conventional highly hard polishing agent at all, is lower in hardness (Hv) than the probe tip  20   b  of the probe  20 , and has the surface  44   a  conforming to the surface  42   a  of the base plate  42 . Accordingly, by letting the probe tip  20   b  of the probe  20  slide on the surface  44   a  of the surface layer  44  of the cleaning apparatus  40 , foreign matters can be removed effectively without causing significant abrasion of the probe tip  20   b.    
         [0039]    As the base plate  42 , an amorphous carbon plate, a silicon carbide plate, a ceramic plate, or the like can be used instead of the aforementioned silicon plate. 
         [0040]    Also, the surface layer  44  can be formed by deposition of copper, a copper alloy, tungsten, a tungsten alloy, chromium, or a chromium alloy. The surface layer  44  is preferably one that is hard enough for the probe tip  20   b  of the probe  20  not to stick in the surface layer  44  when the probe tip  20   b  of the probe  20  is thrust toward the surface layer  44  at the time of cleaning of the probe  20  and that is less harder than the probe tip. Therefore, the material for the surface layer is determined by the relation with the hardness of the material for the probe tip. 
         [0041]    Also, the surface layer  44  can be formed by deposition of an insulating material such as a gelled material or a silicon nitride film as well. 
         [0042]    The present invention is not limited to the above embodiments but may be altered in various ways without departing from the spirit and scope of the present invention.