Abstract:
A probe card includes a first probe plate having a first plurality of tapered apertures formed therein. Each of the tapered apertures has a first opening that is smaller than a second opening. The first openings and the second openings are on opposite surfaces of the first probe plate. The probe card further includes a second probe plate having a second plurality of tapered apertures formed therein. Each of the tapered apertures has a first opening that is smaller than a second opening. The first openings and the second openings are on opposite surfaces of the second probe plate. The surfaces having the second openings are disposed adjacent to one another. Pairs of the tapered apertures of the first and second probe plates substantially align. The probe card further includes a plurality of probes, wherein each of the probes is disposed in one of the pairs of the tapered apertures.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to integrated circuit technology. More particularly, the present invention relate to a test method and test apparatus for integrated circuit technology. 
         [0002]    Integrated circuits (ICs) are typically tested prior to being used in an application, such as a circuit board. IC testing is often performed on wafers prior to packaging, after the ICs are packaged, and are often tested once soldered onto a circuit board. Finished products that include ICs are also often tested prior to shipping to consumers, and these finished products tests often further test of the ICs of these products. 
         [0003]    Testing an IC at the wafer level typically includes contacting a probe card to pads on the IC and driving electrical signals into and receiving electrical signal from the IC. More specifically, the probe card&#39;s probes are configured to contact to the bond pads of the IC to drive and receive the electrical signals. The electrical signals received from the IC are typically generated by the IC in response to the electrical signal driven into the IC by the probe card. The electrical signals driven into the probe card and the IC are often generated by a signal generator, such as an automated test equipment (ATE) machine. The ATE machine may also be configured to receive the electrical signal from the IC via the probe card and compare the received electrical signal with known good (i.e., passing) and/or bad (i.e., failing) test patterns to determine whether the IC will be packed or rejected from packaging. 
         [0004]    Relatively early generation probe cards were configured to contact and test a single IC (or die) on a wafer. These early probe cards often included tungsten probes that were substantially horizontally disposed and bent at the tips of the probes to contact the bond pads of the IC. Latter versions of these probe cards often included sets of probes that were often diagonally disposed to test two or more ICs in a single touch down of the probe card to the wafer. One draw back of both of these early generation probe cards is the limited number of ICs that can be tested in a single touch down. This draw back has become significant as IC manufacturer&#39;s would like to test all or a substantial percentage of the ICs on a wafer in a single touch down of the probe card to the wafer. 
         [0005]    Therefore, new probe card methods and new probe apparatus are needed for testing wafers wherein a relatively large percentage of ICs on a wafer are tested in a single touch down of the probe card to the wafer. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a new test method and test apparatus for integrated circuit technology. More particularly, the present invention provides a probe card configured to transfer test signal to and receive test signal from an integrated circuit. 
         [0007]    According to one embodiment of the present invention, the probe card includes a first probe plate having a first plurality of tapered apertures formed therein. Each of the tapered apertures has a first opening that is smaller than a second opening. The first openings and the second openings are on opposite surfaces of the first probe plate. The probe card further includes a second probe plate having a second plurality of tapered apertures formed therein. Each of the tapered apertures has a first opening that is smaller than a second opening. The first openings and the second openings are on opposite surfaces of the second probe plate. The surfaces having the second openings are disposed adjacent to one another. Pairs of the tapered apertures of the first and second probe plates substantially align. The probe card further includes a plurality of probes, wherein each of the probes is disposed in one of the pairs of the tapered apertures. 
         [0008]    According to a specific embodiment of the present invention, the surface of the second probe plate that includes the first openings is a first surface of the probe card, and a second end of each of the probes is configured to extend from the first surface of the probe card. 
         [0009]    According to another specific embodiment, the probe card further includes a space transformer that includes a plurality of pads disposed on a first surface of the space transformer, wherein each of the pads is configured to contact a first end of each of the probes. Each probe includes a lateral support that is configured to permit the force applied to the probe by the space transformer to be different than the force applied to the probe by a bond pad of an integrated circuit. According to a specific embodiment, a portion of each probe between the space transformer and the lateral support is constrained with a higher compression force than a compression force applied to the probe by a bond pad. The space transformer includes a second plurality of pads disposed on a second surface, which is disposed opposite the first mentioned surface of the space transformer. 
         [0010]    According to a specific embodiment of the present invention, the probe card further includes a printed circuit board (PCB) coupled to the space transformer, wherein the PCB includes a plurality of pads, which is configured to respectively couple to the second plurality of pads of the space transformer. The density of the plurality of pads of the PCB is less than a density of the first plurality of the pads of the space transformer. 
         [0011]    According to another specific embodiment of the present invention, each probe includes a lateral support that is configured to couple to a surface of the first probe plate that includes the first opening of the first probe plate. The lateral support of each of the probes is configured to inhibit the probe from dislodging from the first and second probe-plates. The lateral support is straight, curved, and/or has a spring configuration. Each of the probes includes a top portion that has a spring configuration and the top portion is configured to flex if the probe is pressed by the space transformer. The top portion is straight, coiled, or serpentined. Each probe includes a bottom portion that has a spring configuration and the bottom portion is configured to flex if the probe presses a bond pad of an integrated surface. The bottom portion is straight, coiled, or serpentined. The first and the second pluralities of tapered apertures of the top and bottom-probe plates are formed by laser ablation. 
         [0012]    A better understanding of the nature and advantages of the present invention may be gained with reference to the following detailed description and the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIGS. 1A and 1B  are simplified side and bottoms views of a probe card according to one embodiment of the present invention; 
           [0014]      FIG. 2  is an enlarged, cross-sectional view of a portion of the probe card shown  FIGS. 1A and 1B ; 
           [0015]      FIG. 3  is a simplified side view of a variety of probes according to a variety of embodiments of the present invention; 
           [0016]      FIG. 4  is a simplified cross-sectional view of a portion of a probe card according to another embodiment of the present invention; 
           [0017]      FIG. 5  is a simplified cross-sectional view of a portion of a probe card according to another embodiment of the present invention; and 
           [0018]      FIG. 6  is a simplified cross-sectional view of a probe card according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIGS. 1A and 1B  are simplified side and bottoms views of a probe card  100  according to one embodiment of the present invention. The probe card includes a top probe plate  105 , a bottom probe plate  110 , and a plurality of probes  115 . The probes are labeled with the base reference numeral  115  and an alphabetic suffix. The probe card may also include space transformer  120  and a printed circuit board (PCB)  125 . For convenience, probe card  100  is not shown to scale in  FIGS. 1A and 1B  but is shown for convenience. 
         [0020]    The plurality of probes  115  is be configured to contact one or more of the ICs on a wafer. According to a specific embodiment of the present invention, the plurality of probes is configured to contact all of the ICs on the wafer so that all the ICs on the wafer may be tested in a single touch down of the probe card to the wafer. More specifically, the plurality of probes may be configured to contact the bond pads of the ICs on a wafer. Each probe may be configured to contact one bond pad of an IC. The probes may be configured to contact one or more of the bond pads of an IC. It should be understood that the pattern of probes shown in  FIGS. 1A and 1B  is exemplary, and that the probes may be arranged in nearly any pattern to substantially match the bond pads of an IC. 
         [0021]      FIG. 2  is an enlarged, cross-sectional view of a portion  200  (see  FIG. 1A ) of probe card  100 . For convenience, one probe  115   a  is shown in portion  200  in  FIG. 2 . It should be understood that each of the probes may be similarly disposed in the probe card. According to one embodiment of the present invention, probe  115   a  is disposed in a first hole  105   a  formed in the top probe plate and a second hole  110   a  formed in the bottom probe plate. The holes of the top and bottom probe plates may be substantially vertically aligned so that the probe is substantially vertically oriented. 
         [0022]    According to one embodiment of the present invention, each of the holes (e.g., holes  105   a  and  110   a ) formed in the top and bottom probe plates are formed via a laser ablation (or laser drilling) process. In a typical laser drilling process, at the surface on which the laser enters the material being drilled, the entry portion (e.g., entry portion  105   a ′) of the hole is larger than the exit portion (e.g., exit portion  105   a ″) of the hole. The holes may be substantially round or oblong. For example, if the holes are oblong the entrance portion or the exit portion may be 100 microns by 30 microns or the like along the longest and shortest open portions of the entrance portion or the exit portion. According to one embodiment, the top probe plate and the bottom probe plate are disposed such that the entrance surfaces (i.e., the surface associated with the entry of the laser into the material) of these probe plates are adjacent to one another. The exit surfaces (i.e., the surface associated with the exit of the laser from the material) face away from one another. As such, the smaller exit portions of the holes are further apart than the larger entrance portions of the holes. Spacing the exit holes relatively far from one another provides a relatively high lateral stability of the probes. 
         [0023]    According to one embodiment, the space transformer is configured to decrease the density and/or the pitch of the electrical contacts of the probe cards. More specifically, the plurality of probes might have a first density (or probe density) and/or first pitch (i.e., probe pitch) that are respectively higher than a second density (or PCB contact density) and/or second pitch (i.e., PCB contact pitch) of a plurality of PCB contact pads  205  that are disposed on the bottom surface of the PCB. Contact pads  205  are annular rings according to one embodiment of the present invention. One contact pad  205   a  is shown in  FIG. 2 . More specifically yet, referring to  FIG. 2 , the space transformer includes a bottom-contact pad  210  for each probe (e.g., probe  115   a ). According to the example being considered, a first tip  115   a ′ of probe  115   a  is configured to contact the bottom-contact pad  210 . A second tip  115   a ″ of the probe is configured to extend from the bottom of the probe card and to contact a bond pad of a wafer. Bottom-contact pad  210  of the space transformer may be coupled to a trace  215 , which is disposed on the bottom surface of the space transformer. Trace  215  may be coupled to a via  220 , which extends from the bottom surface of the space transfer to the top surface of space transformer. The via may be coupled to a top-contact pad  225  that is disposed on the top surface of the space transformer. While trace  215  is shown in  FIG. 2  as being disposed on the bottom surface of the space transformer, the trace may be disposed on the top surface of the space transformer or may be disposed on an inner layer of the space transformer. Various traces of the space transformer may be disposed on the top surface, the bottom surface, and/or in inner layers. According to one embodiment, at least one bottom-contact pad of the space transformer is coupled to a via of the space transformer that is in turn coupled to a top-contact pad of the space transformer without an intervening trace (e.g., see in  FIG. 1  the top and the bottom contact pads associated with probe  115   d , and see the via that couples these contact pads). 
         [0024]    According to one embodiment, the top-probe plate and the bottom-probe plate are coupled by one or more fasteners  230 , such as screws, clamps, or the like (see  FIG. 1A ). The PCB and space transformer may be coupled by one or more fasteners, such as screws, clamps, or the like. The coupled PCB and space transformer may then be coupled to the top and bottom-probe plates by one or more fasteners  235 , such as screws, clamps, or the like. The coupled PCB and space transformer may be separable from the top-probe plate and the bottom-probe plate to permit the relatively easy change of one or more probes. For example, probes may be replaced is they are damaged, the lengths of the probes are changed or the like. 
         [0025]      FIG. 3  is a simplified side view of a variety of probes according to a variety of embodiments of the present invention. The probes have a variety of shapes according to various embodiments. For example, probe  300  includes a top-spring portion  305 , a lateral support  310 , and a bottom-spring portion  315 . The top and bottom-spring portions may be coiled, serpentined, or the like to permit these portions of the probe to vertically compress. For example, the top-spring portion may compress as the space transformer is coupled to the top and bottom-probe plates. The bottom spring portion may be configured to compress as the probe contacts the bond pad of an IC. Lateral support  305  may be configured to contact the exit surface of the top-probe plate to prevent the probe from falling out of the probe card. 
         [0026]    Further, probe  330  includes a top portion  335  and a bottom portion  340  that are straight. Probe  330  may also include a lateral support  310  (describe above). The top and bottom portions of probe  330  might be configured to laterally bend under linear compression forces (e.g., a force that is substantially along a longitudinal axis of the probe). The lateral bend of the top or bottom portion of the probe provides a spring action for the probe. For example, as the space transformer is coupled to the top and bottom-probe plates, and as the bottom-contact pads  210  press on the tips  115   a ′ of the probes (e.g., the top portion of probe  330 ), the top portions of the probes might be configured to laterally bend under the compression force. The bottom portions of the probes  330  might be configured to laterally bend as the probes are pushed to contact the bond pads of an IC. According to one embodiment, the bottom-contact pads of the space transformer press on the tip of the probes with sufficient force such that the tips of the probes are held to the space transformer&#39;s bottom-contact pads and substantially do not scratch the bottom-contact pads. That is, each tip contact its associated bottom-contact pad of the space transformer in an area that is about the size of the tip, and the tip substantially does not move from the area so that the bottom-contact pad of the space transformer is not scratched. For example, as the probes are pushed to contact the bonding pads of a wafer, the tip of the probes in contact with the bottom-contact pads of the space transformer will substantially not scratch the bottom-contact pads. The top portion of each pin that is between the space transformer and the lateral support is constrained with a higher compression force, which is applied by the space transformer, than the compression force on the bottom portion of the probes that is applied by pushing the probes into contract with bond pads of a wafer. 
         [0027]    Probe  350  includes a lateral support  355  that is curved and that may be configured to compress as the space transformer is coupled to the top and bottom-probe plates. Probe  360  includes a lateral support  365  that includes two curved portions that may be configured to compress as the space transformer is coupled to the top and bottom-probe plates. Probe  370  has a step shape that is provided by a lateral support  375 . The probes shown in  FIG. 3  are exemplary and those of skill in the art will know of other useful probes and these probes are considered to be within the scope and purview of the present invention. Each of probes  350 ,  360 , and  370  includes straight top and bottom portions, such as those of probe  330  described above. Alternatively, probes  350 ,  360 , and  379  may include top and/or bottom portions that have coil shapes, serpentine shapes or the like, such as those top and bottom portions of probe  300  discussed above. 
         [0028]    Probe  380  includes a bottom portion  382  that may be coiled, serpentine, or the like, and includes a top portion that may include a first laterally bent portion  384  and/or a second laterally bent portion  386 . Probe  380  may include a lateral support  388 . 
         [0029]    Probe  390  includes a bottom portion  392  that may be arced with a single arc, and includes a top portion  394  that includes a one or more arced portions. Probe  390  may include a lateral support  388 . 
         [0030]    Probe  395  includes a bottom portion  397  that may be a spring, such as a micro spring, and includes a top portion  398  that me be a spring, such as a micro spring. The micro springs may be of the type manufactured by Microfabrica Inc. of Van Nuys, Calif. A tip  399  that is substantially vertical (e.g., vertical with respect to the plane of the drawing sheet) may coupled to the tip of each spring. Probe  390  may include a lateral support  388 . 
         [0031]      FIG. 4  is a simplified cross-sectional view of a portion  400  of a probe card according to another embodiment of the present invention. The probe card to which probe card portion  400  belongs differs from the probe card embodiments described above in that the probe card includes a set of spacers  410  disposed between the top-probe plate and the bottom-probe plate. A set as referred to herein includes one or more members. The spacers are configured to provide a space between the top and bottom-probe plates. The space provided by the spacers may be configured to permit probes of a variety of lengths to be used with the probe card. The space provided by the spacers may also permit relatively more lateral bend of the probes. 
         [0032]      FIG. 5  is a simplified cross-sectional view of a portion  500  of a probe card according to another embodiment of the present invention. The probe card to which probe card portion  500  belongs differs from the probe card embodiments described above in that the probe card includes a spacer  510  disposed between the top-probe plate and the bottom-probe plate. A plurality of holes is formed in the spacer and each hole is located at a position where one of the probes is located. Similar to the set of spacers  510  described above, spacer  510  is configured to permit probes of a variety of lengths to be used with the probe card, and may also permit relatively more lateral bend of the probes. 
         [0033]      FIG. 6  is a simplified cross-sectional view of a probe card  600  according to another embodiment of the present invention. The same numeral scheme used in  FIG. 1A  is used in  FIG. 6  to identify substantially similar parts of probe cards  100  and  600 . Probe card  600  differs from the probe cards described above in that probe card  600  includes a spacer plate  605 . Spacer plate  605  is positioned between space transformer  120  and top probe plate  105 . A plurality of holes  610  are formed in the space transform. The holes may be formed by laser drilling or by other methods. Holes  610  are formed so that the top portions of the probes fit through the holes. Probe card  600  may includes spacers  410  or  510 . 
         [0034]    According to one embodiment of an assembly method for assembling anyone of the foregoing described probe cards, first, the top-probe plate and the bottom-probe plate may be coupled. The top-probe plate and the bottom-probe place may be moved laterally with respect to one another as or after these probe plates are coupled. The top-probe plate and/or the bottom-probe plate may be coupled to one or more stages (e.g., micrometer stages) that are configured to laterally translate these plates in one or more lateral directions. The plates may be laterally moved by the one or more stages to adjust the positions of the holes in the top-probe plate relative to the holes in the bottom-probe plate. Via the movement of these holes relative to one another, the vertical angles of the probes may be adjusted and thereby, the positions of the tips of the probes may be adjusted to align the probes with a set of bond pads on a wafer. While the foregoing embodiment is described as including the use of stages to move the top and bottom-probe plates relative to one another, these plates might be moved and/or aligned by other methods that will be well known to those of skill in the art and are to be considered within the scope and purview of the present invention. Subsequent to coupling the top-probe plate to the bottom-probe plate, the probes may be placed in the holes formed in these plates. Thereafter, the space transformer may be coupled to the assembled top and bottom-probe plates. The PCB may then be coupled to the space transformer. Alternatively, the coupled PCB and space transformer may be coupled as a single unit to the top and bottom-probe plates. The spacers and/or the spacer plate may be coupled to their associated components at the various assembly steps as will be understood by those of skill in the art. 
         [0035]    According to one embodiment, the space transformer is a ceramic or flexible circuit board, and may be a low temperature co-fired ceramic (LTCC). The PCB may be formed from a variety of well known materials such as fiber glass, polyimide, polyester or the like. The probes may be tungsten, nickel, beryllium copper, a combination of the foregoing or other known probe material. 
         [0036]    It is to be understood that the exemplary embodiments described above are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. Therefore, the above description should not be understood as limiting the scope of the invention as defined by the claims.