Abstract:
A probe card  2  for an IC testing apparatus electrically connected to a test head board  11  of the IC testing apparatus and having a plurality of needle contacts  211  provided on a main surface for electrical contact with a device under test, wherein a plurality of zero insertion force connectors electrically connected to the needle contacts are provided at substantially radial positions from the position where the needle contacts are provided.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an IC testing apparatus for testing a semiconductor integrated circuit device or other various types of electronic devices (hereinafter referred to as an “IC” as a representative example), more particularly relates to a probe card used for connecting a test head and a device under test. 
     2. Description of the Related Art 
     A large number of semiconductor integrated circuit devices are formed on a silicon wafer etc., then go through various processes such as dicing, wire bonding, and packaging to complete electronic devices. Such ICs are tested operationally before shipment. These tests of the ICs are conducted in either the state of the completed products or the wafer state. 
     As an IC testing apparatus for testing ICS in the wafer state, there is known the one disclosed in Japanese Utility Model Publication (Kokai) No. 5-15431, for example. In this IC testing apparatus, zero insertion force connectors are attached to reduce the force for pressing a probe card provided with needles (pin contacts) from the test head and thereby poor contact due to deformation of the probe card is prevented. 
     In the conventional probe card, however, since the distance from the needles to the contacts of the zero insertion force connectors connected to the same was uneven, there was the problem that the impedances of the wiring patterns differed and the electrical characteristics fluctuated. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a probe card for an IC testing apparatus superior in electrical characteristics. 
     (1) According to the present invention, there is provided a probe card for an IC testing apparatus to be electrically connected to a test head board of the IC testing apparatus and having a plurality of needle contacts for electrical contact with a device under test provided on its main surface, 
     wherein a plurality of connectors electrically connected to said needle contacts are provided at substantially radial positions from the position where said needle contacts are provided. 
     In this invention, the connector is not particularly limited, but preferably the connector is zero insertion force connector. 
     In the probe card for an IC testing apparatus of the present invention, since the connectors are provided at substantially radial positions from the position where the needle contacts are provided, the distance between the needle contacts and the contacts of the connectors connected to them can be set uniformly. Therefore, it is possible to make the impedances of the wirings from the needle contacts to the connectors uniform and thereby possible to suppress fluctuations in the electrical characteristics. 
     The “substantially radial positions” of the present invention mean positions or areas of substantially equal distances (distances from center point) fanning out radially from the position or area where the-needle contacts are provided and do not mean strict radial shapes geometrically. The point is that the all positions are included where the impedances of the wiring connecting the needle contacts and contacts of the connectors become uniform enough not to have an effect on the electrical characteristics of the probe card. (2) In the above invention, the specific means for arranging the zero force connectors substantially radially from the position where the needle contacts are provided is not particularly limited, but as one embodiment, it is possible to mention a probe card for an IC testing apparatus wherein a board is formed in a circular shape, said needle contacts are provided at the substantial center of the board, and said parts of the zero insertion force connectors are provided at outer circumferential edges of the board. 
     When the device under test is a logic type IC etc., a small number of one or two devices under test are often simultaneously measured, but in this case the main surface of the board can be used efficiently and the distance between the needle contacts and zero insertion force connectors can be easily laid out uniformly by providing the needle contacts at the substantial center of the board and providing the zero insertion force connectors at the outer circumferential edges of the board. 
     The “zero insertion force connectors” referred to in the present invention mean connectors of a type not requiring application of force in the direction or insertion or withdrawal when inserting together or pulling apart parts of the zero insertion force connectors. The specific structure is not particularly limited. 
     Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will be explained in more detail below with reference to the attached drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is an exploded perspective view of key parts showing a test head of an IC testing apparatus to which the probe card of the present invention is applied; 
     FIG. 2 is a sectional view of the state of a probe card of FIG. 1 attached to the test head; and 
     FIG. 3 is a plan view of the probe card of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be explained below based on the drawings. 
     As shown in FIG. 1, the devices under test, that is, wafer ICs, are a large number of semiconductor circuits formed integrated on a single wafer. When testing them, the wafer is held by vacuum by a wafer chuck  3  and held in a state positioned with a high accuracy. 
     A card holder  4  positioned above the wafer chuck  3  is formed with a circular through hole  41  at its center. Around the circumferential edge of the through hole  41  is formed a step  42  for holding the probe card  2 . This card holder  4  is affixed to a ring carrier  43  as shown in FIG.  2 . It is positioned with respect to the later mentioned top plate  11  by insertion of guide pins  44  provided at the ring carrier  43  side into guide bushes  13  provided at a top plate  11  side. 
     The probe card  2  of this embodiment has a circularly formed board and is provided at the substantial center of its main surface (bottom surface in FIG.  1  and FIG. 2) with two needle groups  21  (corresponding to pin contacts of the present invention) so as to enable simultaneous measurement of two ICs. These two needle groups  21  are shaped corresponding to the shapes of the ICs formed on the wafer (square shapes in the example illustrated) arranged in two diagonally from each other (offset from each other) as shown in FIG.  3 . 
     One of the needle groups  21  among these is provided with exactly the number of needles  211  for contact with the terminals of one IC formed on the wafer (contacts in state before wire bonding). As shown in FIG. 2, the front ends of the needles  211  face the wafer IC side, while the other ends are affixed to the board of the probe card  2 . 
     Note that the two needle groups  21  are arranged diagonally from each other as illustrated to avoid the needles  211  from interfering with each other. Further, in this embodiment, the example of measurement of two ICs simultaneously was mentioned, but the probe card  2  of the present invention is not limited in any way as to the number of ICs simultaneously measured. It may also be a type measuring one IC or simultaneously measuring three or more ICs. 
     In the probe card  2  of the present embodiment, parts  22   a  of zero insertion force connectors are attached at substantially equal intervals at the outer circumferential edges of the main surface (top surface in FIG.  1  and FIG. 2) of the opposite side of the board. 
     The “zero insertion force connectors” mean connectors of a type not requiring application of force in the direction of insertion or withdrawal (vertical direction in this example) when inserting or pulling parts into or out of other zero insertion force connector parts  22   b  provided at the later explained contact ring. It is possible to use ones of a type where a slider is used to move a rail built in the connector in the longitudinal direction back and forth to move a cam engaged with the rail up and down and use that vertical movement of the cam to reduce or increase the distance between socket contacts gripping the pin contacts or ones of another type. 
     Note that the needles  211  and contacts of the zero insertion force connectors  22   a  are electrically connected by wiring patterns or through holes (both not shown in the figures) formed on or in the board of the probe card  2 . 
     On the other hand, the test head  1  of the IC testing apparatus is positioned above the wafer chuck  3 . While not illustrated, various boards are provided here, such as the performance board. At the bottommost surface of the test head  1  is affixed a top panel  11  as shown in FIG.  1  and FIG.  2 . Further, a contact ring  12  is affixed to the bottom surface of the top panel  11 . 
     The contact ring  12  of the present embodiment is formed in a ring shape as shown in FIG.  1 . The other parts  22   b  of the zero insertion force connectors explained above are affixed at the partially sectoral shaped through holes  121  formed at its outer circumference. The sectional view of FIG. 2 shows the state of attachment of the zero insertion force connectors  22   b.    
     Further, the probe card  2  and the contact ring  12  are positioned with respect to each other by making guide pins  23  provided at the probe card  2  side engage with guide bushes  122  provided at the contact ring  12  side. 
     Note that while not illustrated, the zero insertion force connector parts  22   b  attached to the contact ring  12  side and the performance board in the test head  1  are electrically connected by a large number of wires or daughter boards. 
     Next, the operation will be explained. 
     When testing wafer ICs, first the wafer held by suction by the wafer chuck  3  while positioning it. In that state, the wafer chuck  3  is positioned in the X-Y plane so that the needles  211  of the probe card  2  will contact the contacts of two target ICs and made to rise. Due to this, the first two ICs are tested. When the test is completed, the wafer chuck  3  is made to descend slightly, then the wafer chuck  3  is positioned in the X-Y plane so that the needles  211  of the probe card  2  will contact the contacts of the next two ICs and again made to rise. This operation is repeated to test the wafer ICs in all of the regions. 
     In particular, since the probe card  2  of the present embodiment is provided with two needle groups  21 ,  21  arranged at the center of the circular board and is provided with parts  22   a  of the zero insertion force connectors arranged at the outer circumferential edges of the circular board, the distances of the wiring patterns to electrically connect with the same become substantially equal at all needles  211 . Therefore, the impedances of the wiring patterns reaching from the needles  211  to the contacts of the zero insertion force connectors  22   a  become uniform and therefore the fluctuation in electrical characteristics becomes remarkably smaller. 
     Note that the embodiment explained above was described to facilitate understanding of the present invention and was not described to limit the present invention. Therefore, elements disclosed in the above embodiment include all design modifications and equivalents belonging to the technical field of the present invention.