Patent Publication Number: US-7719296-B2

Title: Inspection contact structure and probe card

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This is a division of application Ser. No. 11/270,444, filed Nov. 10, 2005, now U.S. Pat. No. 7,267,551 which is incorporated in its entirety herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an inspection contact structure to contact with an object electrically to be inspected to inspect electric properties of the object to be inspected, and a probe card. 
   2. Description of the Related Art 
   Inspection of electric properties of an electronic circuit such as an IC, LSI, or the like formed, for example, on a semiconductor wafer is performed by bringing, for example, a plurality of probe needles arranged on the lower surface of a probe card into electrical contact with electrode pads of the electronic circuit on the wafer. Therefore, the probe needles need to be arranged in alignment with the positions of the respective electrode pads. 
   However, the pattern of the electronic circuit has become finer in which the electrode pads have been made finer and intervals between the electrode pads have become smaller. This requires formation of fine contact portions at a narrow pitch, such as those with a width dimension of 100 μm or less and at a pitch of 180 μm or less. Hence, use of an anisotropic conductive sheet instead of the probe needles is proposed (Japanese Patent Application Laid-open Publication No. H03-196416 (U.S. Pat. No. 3,038,859)). The anisotropic conductive sheet is a sheet having a plurality of elastic conductive portions protruding from one surface of the sheet being an insulating portion, in which the conductive portions can be formed very fine at a narrow pitch. 
   However, when the above-described anisotropic conductive sheet is simply used, the conductive portions have limitations in dimension in the height direction because the conductive portions are formed fine at a narrow pitch, resulting in small displacement in the height direction presented by the elasticity of the conductive portions. As a result, the conductive portions cannot absorb, by their elasticity, variations in height of a number of electrode pads on the wafer surface, thus causing unstable contact between the conductive portions and the electrode pads within the wafer surface. Further, the inclination and distortion on the probe card side occurring due to attachment or thermal expansion of the probe card cannot be sufficiently absorbed by the elasticity of the conductive portions, resulting in unstable contact of the electrode pads within the wafer surface. 
   SUMMARY OF THE INVENTION 
   The present invention has been developed in consideration of the above points and its object is to provide an inspection contact structure and a probe card in which contact portions to an object to be inspected such as a wafer can be made very fine at a narrow pitch, and contact with the object to be inspected can be stable. 
   To achieve the above object, the present invention is an inspection contact structure to contact with an object electrically to be inspected to inspect electric properties of the object to be inspected, the inspection contact structure including: a substrate in a flat plate shape; and sheets respectively attached to both surfaces of the substrate, each of the sheets including a plurality of elastic conductive portions and insulating portions each interconnecting the conductive portions. The conductive portions are formed to pass through the sheet and protrude from both surfaces of the sheet, and the substrate is formed with a plurality of current-carrying paths linearly passing through the substrate in a thickness direction in a manner to correspond to the conductive portions. The conductive portions of the sheets on both surfaces of the substrate are in contact with end portions of the respective corresponding current-carrying paths in a manner to have the current-carrying paths sandwiched therebetween. 
   According to the present invention, a sheet is used which is formed with a number of conductive portions within the sheet surface, so that very fine contact portions at a narrow pitch can be realized. Since the sheets are respectively attached to both surfaces of the substrate, the conductive portions of the sheet on the side of the object to be inspected come into contact with the object to be inspected, so that the elasticity of the conductive portions can absorb variations in height of the object to be inspected. Further, the conductive portions of the sheet on the side opposite to the object to be inspected come into contact with, for example, connecting terminals on the circuit board on the probe card side to which an electrical signal for inspection is applied, so that the elasticity of the conductive portions can absorb distortion and inclination of the whole probe card or the circuit board. Accordingly, even though the contact portions are fine at a narrow pitch, contact with the object to be inspected is stable and the inspection of the electric properties is appropriately performed. 
   The conductive portions of the sheets on both surface of the substrate and the current-carrying paths in the substrate may be arranged on same axes. In this case, when the object to be inspected is pressed against and brought into contact with the conductive portions of one of the sheets, force acts on the substrate on the same axes passing from the conductive portions on both surfaces through current-carrying paths. Therefore, only opposing couple force in the thickness direction but no moment can act, thereby preventing breakage of the substrate. The effect is significantly presented particularly when using a very thin substrate with a thickness of 1 mm or less. 
   The sheet may be fixed to a frame formed along an outer peripheral portion of the sheet and fixed to the substrate via the frame. In this case, the deflection and distortion of the sheet itself can be suppressed so that the sheet can be made to follow the surface of the substrate. As a result of this, uniform contact can be realized by the conductive portions within the sheet surface. 
   The frame may be bonded to the substrate with a silicone adhesive. In this case, the frame can be relatively easily detached from the substrate, thus allowing replacement and maintenance of the sheet to be easily performed. 
   Tapered contactors that come into contact with the object to be inspected may be attached to tip portions of the conductive portions of the sheet located on the side of the object to be inspected. In this case, the contact pressure to the object to be inspected increases, whereby the electrical contact with the object to be inspected can be more stable. Further, since the conductive portions never come into direct contact with the object to be inspected, wear of the conductive portions can be prevented. 
   The present invention according to another aspect is a probe card for inspecting electric properties of an object to be inspected, the card including: a circuit board; and an inspection contact structure provided between the circuit board and the object to be inspected, for passing current between the object to be inspected and the circuit board. The inspection contact structure includes: a substrate in a flat plate shape; and sheets respectively attached to both surfaces of the substrate, each of the sheets composed of a plurality of elastic conductive portions and insulating portions each interconnecting the conductive portions. The conductive portions are formed to pass through the sheet and protrude from both surfaces of the sheet, and the substrate is formed with a plurality of current-carrying paths linearly passing through the substrate in a thickness direction in a manner to correspond to the conductive portions. The conductive portions of the sheets on both surfaces of the substrate are in contact with end portions of the respective corresponding current-carrying paths in a manner to have the current-carrying paths sandwiched therebetween, and the inspection contact structure is configured to be freely attached to/detached from the circuit board. 
   In this case, the above-described inspection contact structure is freely attached to/detached from the circuit board, so that the inspection contact structure can be detached to allow, for example, maintenance of the inspection contact structure such as replacement of the sheet to be easily performed. 
   The inspection contact structure may be bonded to the circuit board with a silicone adhesive. In this case, the inspection contact structure can be easily detached from the circuit board. 
   Further, the circuit board may be formed with suction ports for sucking the substrate of the inspection contact structure. In this case, stop of the suction through the suction ports allows the inspection contact structure to be freely attached to/detached from the circuit board. 
   According to the present invention, inspection of the electric properties of the object to be inspected can be stably performed, so that defects in electronic devices can be surely detected to improve their quality. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an explanatory view of a longitudinal section showing a schematic configuration of a probe device; 
       FIG. 2  is an explanatory view of a longitudinal section showing a configuration of an inspection contact structure; 
       FIG. 3  is a plan view of a sheet; 
       FIG. 4  is an explanatory view of a structure of the sheet; 
       FIG. 5  is an explanatory view of a longitudinal section of the probe device showing a state in which conductive portions are in contact with electrode pads; 
       FIG. 6  is a plan view of a silicone substrate where a wiring pattern is formed on its upper surface; 
       FIG. 7  is a plan view of a silicone substrate where a wiring pattern is formed on its upper surface; 
       FIG. 8  is an explanatory view of a longitudinal section of a probe device including piping having suction ports; and 
       FIG. 9  is an explanatory view of a longitudinal section of an inspection contact structure having tapered contactors attached thereto. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, a preferred embodiment of the present invention will be described.  FIG. 1  is an explanatory view of a longitudinal section showing a schematic configuration of the inside of a probe device  1  in which an inspection contact structure according to this embodiment is used. 
   In the probe device  1 , for example, a probe card  2  and a mounting table  3  on which a wafer W as an object to be inspected is mounted are provided. The probe card  2  includes a circuit board  10  for transmitting an electrical signal to electrode pads U on the wafer W on the mounting table  3 ; a holder  11  for holding the outer peripheral portion of the circuit board  10 ; and an inspection contact structure  12  attached to the circuit board  10  on the wafer W side which comes into contact with the electrode pads U on the wafer W to pass current between the circuit board  10  and the electrode pads U. 
   The circuit board  10  is formed, for example, in a substantially disk shape. On a lower surface of the circuit board  10 , a plurality of terminals  10   a  for conducting the circuit board  10  with the inspection contact structure  12 . 
   The inspection contact structure  12  includes a silicone substrate  20 , for example, in a shape of a flat plate; a first sheet  21  attached to the upper surface of the silicone substrate  20 ; and a second sheet  22  attached to the lower surface of the silicone substrate  20 . 
   The silicone substrate  20  is formed in a shape of a square flat plate that is thin, for example, about 200 μm to about 400 μm. The silicone substrate  20  is formed with a plurality of current-carrying paths  23  which vertically pass through the silicone substrate  20  from its upper surface to its lower surface as shown in  FIG. 2 . The current-carrying paths  23  are formed such that they correspond one-to-one with the plurality of electrode pads U on the wafer W. Upper connecting terminals  23   a  are formed at the top end portions of the current-carrying paths  23 , while lower connecting terminals  23   b  are formed at the bottom end portions of the current-carrying paths  23 . Note that processing of the silicone substrate  20  is performed by etching process through use of the photolithography technique. 
   Each of the first sheet  21  and the second sheet  22  is an elastic rubber sheet having, for example, a square shape as a whole as shown in  FIG. 3 , and is composed of a plurality of conductive portions  30  densely arranged within the sheet surface and insulating portions  31  each connecting the conductive portions  30 . The plurality of conductive portions  30  are placed at positions to correspond one-to-one with the electrode pads U on the wafer W and the current-carrying paths  23  of the silicone substrate  20  as shown in  FIG. 2 . The insulating portions  31  are formed of, for example, a polymeric substance having insulation performance and elasticity. Each of the conductive portions  30  is formed such that, for example, conductive particles A are densely filled in a polymeric substance having insulation performance and elasticity as shown in  FIG. 4 . The conductive portion  30  is formed in a shape of a square pole passing through the sheet and protruding from both surfaces of the sheet. According to the above configuration, the conductive portions  30  have conductivity in a pressed state and have elasticity in a direction of protrusion from both surfaces of the sheet. For example, the thickness T of the insulating portion  31  is set to, for example, about 100 μm, and the conductive portion  30  is formed such that its height H from the sheet surface is about 30 μm that is 0.3 times the thickness of the insulating portion  31 . The conductive portion  30  is formed such that its width D is, for example, about 85 μm, and the pitch P between adjacent conductive portions  30  is set to about 180 μm. 
   As shown in  FIG. 3 , the outer peripheral portion of each of the first sheet  21  and the second sheet  22  is fixed to, for example, a metal frame  40 . The metal frame  40  has a frame shape along the outer peripheral portion of the sheet  21  or  22 . As shown in  FIG. 2 , supporting portions  41  composed of a silicone adhesive are formed on both surfaces of the outer peripheral portion of the silicone substrate  20 . The metal frame  40  of the first sheet  21  is fixed to the supporting portion  41  on the upper surface of the silicone substrate  20 . The metal frame  40  of the second sheet  22  is fixed to the supporting portion  41  on the lower surface of the silicone substrate  20 . The height of the supporting portion  41  is adjusted so that the conductive portions  30  of the sheet  21  or  22  come into contact with the connecting terminals on the current-carrying paths  23  of the silicone substrate  20  in the pressed state. In other words, the conductive portions  30  of the first sheet  21  abut the corresponding upper connecting terminals  23   a  with the first sheet  21  being fixed to the upper surface side of the silicone substrate  20 . The conductive portions  30  of the second sheet  22  abut the corresponding lower connecting terminals  23   b  with the second sheet  22  being fixed to the lower surface side of the silicone substrate  20 . Accordingly, the conductive portions  30  of the first sheet  21 , the conductive portions  30  of the second sheet  22 , and the current-carrying paths  23  are connected on the same axes in the vertical direction. 
   As shown in  FIG. 1 , the silicone substrate  20  is supported on the lower surface of the circuit board  10  by a supporter  50  placed at a position outside the supporting portion  40  on the upper surface of the silicone substrate  20 . The supporter  50  is composed of, for example, a silicone adhesive. The height of the supporter  50  is adjusted so that the top end surfaces of the conductive portions  30  of the first sheet  21  come into contact with the connecting terminals  10   a  of the circuit board  10  in a pressed state. 
   The mounting table  3  is configured to be movable, for example, laterally and vertically to be able to move the wafer W mounted thereon in three-dimensional directions. 
   In the probe device  1  configured as described above, the wafer W is mounted at a predetermined position on the mounting table  3 , and the mounting table  3  subsequently moves so that the electrode pads U on the wafer W come into contact with the corresponding conductive portions  30  of the second sheet  22 . An electrical signal for inspection is then supplied from the circuit board  10  to the electrode pads U through the conductive portions  30  of the first sheet  21 , the current-carrying paths  23 , and the conductive portions  30  of the second sheet  22  in the inspection contact structure  12  in order, to inspect electric properties of a circuit on the wafer W. 
   In the probe device  1  described in the above embodiment, the sheets  21  and  22  are respectively placed on both surfaces of the silicone substrate  20  and the conductive portions  30  of the second sheet  22  are brought into contact with the electrode pads U on the wafer W, so that fine contact portions of 100 μm or less at a pitch of 180 μm or less can be realized. Even though such fine contact portions at a narrow pitch are realized, the conductive portions  30  of the second sheet  22  on the lower surface side of the silicone substrate  20 , for example, can absorb variations in height of the electrode pads U on the wafer W through use of elasticity of the conductive portions  30 . Further, the conductive portions  30  of the first sheet  21  on the upper surface side of the silicone substrate  20  can absorb distortion and inclination of the circuit board  10  through use of the elasticity of the conductive portions  30  so that the horizontality of the inspection contact structure  12  is maintained. This ensures stable contact between the electrode pads U within the wafer surface and the conductive portions  30  of the probe card  2  so that the inspection within the wafer surface can be appropriately performed. 
   When the electrode pads U on the wafer W are pressed against the conductive portions  30 , only an opposing stress in the thickness direction and no deflection moment act on the silicone substrate  20 , since the conductive portions  30  of the first sheet  21  and the second sheet  22  and the current-carrying paths  23  in the silicone substrate  20  are arranged on a straight line in the vertical direction, resulting in prevention of breakage of the very thin silicone substrate  20 . 
   Since the outer peripheral portions of the first sheet  21  and the second sheet  22  are fixed to the metal frames  40  and the metal frames  40  are attached to the supporting portions  41  on the silicone substrate  20 , the sheets  21  and  22  can be made to follow the surfaces of the silicone substrate  20 , while distortion and deflection of the sheets  21  and  22  themselves are prevented. As a result, the contact of the conductive portions  30  within the sheets  21  and  22  can be made uniformly. 
   Since the metal frames  40  of the first sheet  21  and the second sheet  22  are fixed to the silicone substrate  20  with a silicone adhesive, the first sheet  21  and the second sheet  22  can be easily detached from the silicone substrate  20 . Therefore, maintenance and replacement of the first sheet  21  and the second sheet  22  can be easily performed. 
   Further, since the silicone substrate  20  is fixed to the circuit board  10  with a silicone adhesive, the inspection contact structure  12  is attachable to/detachable from the circuit board  10  so that the inspection contact structure  12  can be easily detached from the circuit board  10 . As a result of this, maintenance and replacement of the inspection contact structure  12  can be easily performed. 
   In the above embodiment, since the silicone substrate  20  is used as the substrate to which the sheets  21  and  22  are fixed, a predetermined wiring pattern in which predetermined connecting terminals are connected using metal wires can be formed, for example, on at least any of the upper surface and the lower surface of the silicone substrate  20  by the photolithography technology. For example, particular upper connecting terminals  23   a  may be connected using metal wires  60  on the upper surface of the silicone substrate  20  as shown in  FIG. 6 , or the upper connecting terminals  23   a  on straight lines in a predetermined direction may be connected using metal wires  60  to form parallel connection lines as shown in  FIG. 7 . In this case, the plurality of conductive portions  30  whose upper connecting terminals  23   a  are connected can be used for inspection of, for example, the same electrode depending on the pattern of the electronic circuit on the wafer W. In this case, since inspection of one electrode is performed using the plurality of conductive portions  30 , the inspection is performed with more reliability. Further, the connecting wiring pattern of the upper connecting terminals  23   a  on the silicone substrate  20  can be created depending on the pattern of the electronic circuit, thus making it possible to form the wiring pattern more easily than change of the wiring pattern within the circuit board  10  and to appropriately cope with every pattern of the electronic circuit. Note that a wiring pattern may be formed in which particular lower connecting terminals  23   b  are connected on the lower surface of the silicone substrate  20 . 
   It should be noted that the silicone substrate  20  may be fixed to the circuit board  10  by suction. In this case, the lower surface of the circuit board  10  is provided with pipe paths  71  with suction ports  70  open at their bottom ends. For example, the pipe paths  71  pass through the circuit board  10  of the probe card  2  and are connected to a negative pressure generating device  72  located, for example, outside the probe card  2 . To attach the inspection contact structure  12  to the circuit board  10 , the negative pressure generating device  72  sucks via the suction ports  70  so that the suction force fixes the silicone substrate  20  to the circuit board  10 . To detach the inspection contact structure  12  from the circuit board  10 , the suction by the negative pressure generating device  72  is stopped. In this case, detachment of the inspection contact structure  12  from the circuit board  10  can be easily performed. The inspection contact structure  12  may be attached to/detached from the circuit board  10  by another way, for example, by using magnetic force. 
   When the inspection contact structure  12  is configured to be freely attached to/detached from the circuit board  10  as described above, the inspection contact structure  12  can be easily detached from the probe card  2  and replaced with another. In addition, the conductive portions  30  of the first sheet  21  can absorb distortion and inclination of the circuit board  10  through use of elasticity of the conductive portions  30  as has been described, so that stable contact state can be achieved even if the circuit board  10  has deflection and so on. Accordingly, replacement of the inspection contact structure  12  can be performed without fine adjustment even in an ordinary work environment away from a prober. Further, since the inspection contact structure  12  is fixed at its silicone substrate  20  to the probe card  2  (directly to the circuit board  10 ), contactors (the conductive portions  30  in this embodiment) which come into direct contact with the wafer W can be formed on a desired plane. In short, the inspection contact structure  12  can be made parallel to the probe card  2  without fine adjustment. 
   Contactors for contact with the electrode pads U on the wafer W may be attached to tip portions of the conductive portions  30  of the second sheet  22  described in the above embodiment. In this case, for example, a plurality of contactors  80  in a tapered shape having a sharp tip are arranged to correspond to the conductive portions  30  as shown in  FIG. 9  and held by a holder  81 . The contactors  80  are made of, for example, a conductive metal. The holder  81  is formed in a flat plate shape and formed of an insulating material. The outer peripheral portion of the holder  81  is supported on the lower surface of the silicone substrate  20  by a supporting member  82 , and top end surfaces of the contactors  80  abut the bottom surfaces of the conductive portions  30  in a pressed state. To inspect electric properties of the circuit on the wafer W, the electrode pads U on the wafer W are pressed against the tip portions of the contactors  80  so that the electrical signal from the circuit board  10  is supplied to the electrode pads U via the contactors  80 . In this case, the contact pressure between the contactors  80  and the electrode pads U is large enough to ensure higher stability of the contact. Further, since the conductive portions  30  are not in direct contact with the electrode pads U, wear and breakage of the conductive portions  30  can be prevented. 
   Although one example of the embodiment of the present invention has been described, the present invention is not limited to this example but can take various forms. For example, any shape, number, and arrangement can be appropriately selected for the conductive portions  30  described in the above-described embodiment. The substrate constituting the inspection contact structure  12  is not limited to the silicone substrate but can be, for example, an organic substrate, a silicone dioxide substrate, a glass substrate, and the like which can be subjected to etching process. Further, the present invention is also applicable to a case where the object to be inspected is a substrate other than the wafer W, such as an FPD (Flat Panel Display), a mask reticule for photomask, or the like. 
   The present invention is useful for stably performing inspection of electric properties on portions to be inspected which are fine and provided at a narrow pitch.