Abstract:
A method of producing a contact structure for establishing electrical connection with contact targets. The contact structure is formed of a contactor carrier and a plurality of contactors. The contactor has an upper end oriented in a vertical direction, a straight beam portion oriented in a direction opposite to the upper end and having a lower end which functions as a contact point for electrical connection with a contact target, a return portion returned from the lower end and running in parallel with the straight beam portion to create a predetermined gap therebetween, a diagonal beam portion provided between the upper end and the straight beam portion to function as a spring.

Description:
This is a continuation of U.S. patent application Ser. No. 09/954,333 filed Sep. 12, 2001 now U.S. Pat. No. 6,608,385 which is a continuation-in-part of patent application Ser. No. 09/201,299 filed Nov. 30, 1998, now U.S. Pat. No. 6,297,164, and a continuation-in-part of patent application Ser. No. 09/503,903 filed Feb. 14, 2000, now U.S. Pat. No. 6,540,524, and a continuation-in-part of patent application Ser. No. 09/733,508 filed Dec. 9, 2000, now U.S. Pat. No. 6,471,538. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a contact structure and a production method thereof and a probe contact assembly using the contact structure, and more particularly, to a contact structure having a large number of contactors in a vertical direction and to a method for producing such a large number of contactors on a semiconductor wafer in a horizonal direction and removing the contactors from the wafer to be mounted on a substrate in a vertical direction to form the contact structure such as a contact probe assembly, probe card, IC chip, or other contact mechanism. 
     BACKGROUND OF THE INVENTION 
     In testing high density and high speed electrical devices such as LSI and VLSI circuits, a high performance contact structure such as a probe card having a large number of contactors must be used. In other applications, contact structures may be used for IC packages as IC leads. 
     The present invention is directed to a structure and production process of such contact structures for use in testing and burning-in LSI and VLSI chips, semiconductor wafers and dice, packaged semiconductor devices, printed circuit boards and the like. The present invention can also be applicable to other purposes such as forming leads or terminal pins of IC chips, IC packages or other electronic devices. However, for the simplicity and convenience of explanation, the present invention is described mainly with respect to the semiconductor wafer testing. 
     In the case where semiconductor devices to be tested are in the form of a semiconductor wafer, a semiconductor test system such as an IC tester is usually connected to a substrate handler, such as an automatic wafer prober, to automatically test the semiconductor wafer. Such an example is shown in FIG. 1 in which a semiconductor test system has a test head  100  which is ordinarily in a separate housing and electrically connected to the test system with a bundle of cables  110 . The test head  100  and a substrate handler  400  are mechanically as well as electrically connected with one another with the aid of a manipulator  500  which is driven by a motor  510 . The semiconductor wafers to be tested are automatically provided to a test position of the test head  100  by the substrate handler  400 . 
     On the test head  100 , the semiconductor wafer to be tested is provided with test signals generated by the semiconductor test system. The resultant output signals from the semiconductor wafer under test (IC circuits formed on the semiconductor wafer) are transmitted to the semiconductor test system. In the semiconductor test system, the output signals from the wafer are compared with expected data to determine whether the IC circuits on the semiconductor wafer function correctly. 
     Referring to FIGS. 1 and 2, the test head  100  and the substrate handler  400  are connected through an interface component  140  consisting of a performance board  120  which is a printed circuit board having electric circuit connections unique to a test head&#39;s electrical footprint, coaxial cables, pogo-pins and connectors. The test head  100  includes a large number of printed circuit boards  150  which correspond to the number of test channels (test pins) of the semiconductor test system. Each of the printed circuit boards  150  has a connector  160  to receive a corresponding contact terminal  121  of the performance board  120 . 
     A “frog” ring  130  is mounted on the performance board  120  to accurately determine the contact position relative to the substrate handler  400 . The frog ring  130  has a large number of contact pins  141 , such as ZIF connectors or pogo-pins, connected to contact terminals  121 , through coaxial cables  124 . 
     As shown in FIG. 2, the test head  100  is positioned over the substrate handler  400  and connected to the substrate handler through the interface component  140 . In the substrate handler  400 , a semiconductor wafer  300  to be tested is mounted on a chuck  180 . In this example, a probe card  170  is provided above the semiconductor wafer  300  to be tested. The probe card  170  has a large number of probe contactors (such as cantilevers or needles)  190  to contact with contact targets such as circuit terminals or pads in the IC circuit on the semiconductor wafer  300  under test. 
     Electrodes (contact pads) of the probe card  170  are electrically connected to the contact pins  141  provided on the frog ring  130 . The contact pins  141  are also connected to the contact terminals  121  of the performance board  120  through the coaxial cables  124  where each contact terminal  121  is connected to the corresponding printed circuit board  150  of the test head  100 . Further, the printed circuit boards  150  are connected to the semiconductor test system through the cable  110  having, for example, several hundreds of inner cables. 
     Under this arrangement, the probe contactors (needles)  190  contact the surface (contact target) of the semiconductor wafer  300  on the chuck  180  to apply test signals to the semiconductor wafer  300  and receive the resultant output signals from the wafer  300 . As noted above, the resultant output signals from the semiconductor wafer  300  under test are compared with the expected data generated by the semiconductor test system to determine whether the IC circuits on the semiconductor wafer  300  performs properly. 
     FIG. 3 is a bottom view of the probe card  170  of FIG.  2 . In this example, the probe card  170  has an epoxy ring on which a plurality of probe contactors  190  called needles or cantilevers are mounted. When the chuck  180  mounting the semiconductor wafer  300  moves upward in FIG. 2, the tips of the needles  190  contact the pads or bumps (contact targets) on the wafer  300 . The ends of the needles  190  are connected to wires  194  which are further connected to transmission lines (not shown) formed on the probe card  170 . The transmission lines are connected to a plurality of electrodes (contact pads)  197  which are in communication with the pogo pins  141  of FIG.  2 . 
     Typically, the probe card  170  is structured by a multi-layer of polyimide substrates having ground planes, power planes, signal transmission lines on many layers. As is well known in the art, each of the signal transmission lines is designed to have a characteristic impedance such as 50 ohms by balancing the distributed parameters, i.e., dielectric constant and magnetic permeability of the polyimide, inductances and capacitances of the signal paths within the probe card  170 . Thus, the signal lines are impedance matched establishing a high frequency transmission bandwidth to the wafer  300  for supplying currents in a steady state as well as high current peaks generated by the device&#39;s outputs switching in a transient state. For removing noise, capacitors  193  and  195  are provided on the probe card between the power and ground planes. 
     An equivalent circuit of the probe card  170  is shown in FIG.  4 . As shown in FIGS. 4A and 4B, the signal transmission line on the probe card  170  extends from the electrode  197 , the strip (impedance matched) line  196 , the wire  194 , to the needle  190 . Since the wire  194  and needle  190  are not impedance matched, these portions are deemed as an inductor L in the high frequency band as shown in FIG.  4 C. Because of the overall length of the wire  194  and needle  190  is around 20-30 mm, significant limitations will be resulted from the inductor when testing a high frequency performance of a device under test. 
     Other factors which limit the frequency bandwidth in the probe card  170  reside in the power and ground contactors shown in FIGS. 4D and 4E. If the power line can provide large enough currents to the device under test, it will not seriously limit the operational bandwidth in testing the device. However, because the series connected wire  194  and needle  190  for supplying the power (FIG. 4D) as well as the series connected wire  194  and needle  190  for grounding the power and signals (FIG. 4E) are equivalent to inductors, the high speed current flow is seriously restricted. 
     Moreover, the capacitors  193  and  195  are provided between the power line and the ground line to secure a proper performance of the device under test by filtering out the noise or surge pulses on the power lines. The capacitors  193  have a relatively large value such as 10 μF and can be disconnected from the power lines by switches if necessary. The capacitors  195  have a relatively small capacitance value such as 0.01 μF and fixedly connected close to the DUT. These capacitors serve the function as high frequency decoupling on the power lines. In other words, the capacitors limit the high frequency performance of the probe contactor. 
     Accordingly, the most widely used probe contactors as noted above are limited to the frequency bandwidth of approximately 200 MHz which is insufficient to test recent semiconductor devices. In the industry, it is considered that the frequency bandwidth on the order of 1 GHz or higher, will be necessary in the near future. Further, it is desired in the industry that a probe card is capable of handling a large number of semiconductor devices, especially memories, such as 32 or more, in a parallel fashion to increase test throughput. 
     In the conventional technology, the probe card and probe contactors such as shown in FIG. 3 are manually made, resulting in inconsistent quality. Such inconsistent quality includes fluctuations of size, frequency bandwidth, contact forces and resistance, etc. In the conventional probe contactors, another factor making the contact performance unreliable is a temperature change under which the probe contactors and the semiconductor wafer under test have different temperature expansion ratios. Thus, under the varying temperature, the contact positions therebetween vary which adversely affects the contact force, contact resistance and bandwidth. Thus, there is a need of a contact structure with a new concept which can satisfy the requirement in the next generation semiconductor test technology. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide a contact structure having a large number of contactors for electrically contacting with contact targets with a high frequency bandwidth, high pin counts and high contact performance as well as high reliability. 
     It is another object of the present invention to provide a contact structure such as a probe card for use in testing semiconductor devices and the like which has a very high frequency bandwidth to meet the test requirements in the next generation semiconductor test technology. 
     It is a further object of the present invention to provide a contact structure to establish electrical connection with a large number of semiconductor devices for testing such semiconductor devices in parallel at the same time. 
     It is a further object of the present invention to provide a method for producing a large number of contactors in a two dimensional manner on a silicon substrate, removing the contactors from the substrate and mounting the contactors on a contact substrate in a three dimensional manner to form a contact structure. 
     It is a further object of the present invention to provide a method for producing a large number of contactors in a two dimensional manner on a silicon substrate, transferring the contactors to an adhesive tape and removing the contactors therefrom for vertically mounting the same on a contact substrate to form a contact structure. 
     In the present invention, a contact structure is formed of a large number of contactors produced on a planar surface of a dielectric substrate or a silicon substrate by a photolithography technology. The contact structure of the present invention is advantageously applied to testing and burning-in semiconductor devices, such as LSI and VLSI chips, semiconductor wafers and dice, packaged ICs, printed circuit boards and the like. The contact structure of the present invention can also be used as components of electronics devices such as IC leads and pins. 
     The first aspect of the present invention is a contact structure for establishing electrical connection with contact targets. The contact structure is formed of a contactor carrier and a plurality of contactors. The contactor has an upper end oriented in a vertical direction, a straight beam portion oriented in a direction opposite to the upper end and having a lower end which functions as a contact point for electrical connection with a contact target, a return portion returned from the lower end and running in parallel with the straight beam portion to create a predetermined gap therebetween, a diagonal beam portion provided between the upper end and the straight beam portion to function as a spring. 
     Another aspect of the present invention is a method of producing the contactors in a two dimensional manner on a silicon substrate and removing therefrom for establishing a contact structure. The production method is comprised of the following steps of: 
     (a) forming a sacrificial layer on a surface of a silicon substrate; 
     (b) forming a photoresist layer on the sacrificial layer; 
     (c) aligning a photo mask over the photoresist layer and exposing the photoresist layer with ultraviolet light through the photo mask, the photo mask including an image of the contactors; 
     (d) developing patterns of the image of the contactors on a surface of the photoresist layer; 
     (e) forming the contactors made of conductive material in the patterns on the photoresist layer by depositing the conductive material; each of the contactors having an upper end, a straight beam portion oriented with a lower end as a contact point, a return portion to create a predetermined gap with the straight beam portion, and a diagonal beam portion provided between the upper end and the straight beam portion to function as a spring; 
     (f) stripping the photoresist layer off; 
     (g) removing the sacrificial layer by an etching process so that the contactors are separated from the silicon substrate; and 
     (h) mounting the contactors on a contactor carrier having through holes to receive the contactors therein. 
     A further aspect of the second present invention is a probe contact assembly including the contact structure of the present invention. The probe contact assembly is formed of a contactor carrier having a plurality of contactors mounted on a surface thereof, a probe card for mounting the contactor carrier and establishing electrical communication between the contactors and electrodes provided on the probe card, and a pin block having a plurality of contact pins to interface between the probe card and a semiconductor test system when the pin block is attached to the probe card. Each contactor has a structure as described above with respect to the first aspect of the present invention. 
     According to the present invention, the contact structure has a very high frequency bandwidth to meet the test requirements of next generation semiconductor technology. Since the large number of contactors are produced at the same time on the substrate without involving manual handling, it is possible to achieve consistent quality, high reliability and long life in the contact performance as well as low cost. Further, because the contactors are assembled on the same substrate material as that of the device under test, it is possible to compensate positional errors caused by temperature changes. 
     Further, according to the present invention, the production process is able to produce a large number of contactors in a horizontal direction on the silicon substrate by using relatively simple technique. Such contactors are removed from the substrate and mounted on a contact substrate in a vertical direction. The contact structure produced by the present invention are low cost and high efficiency and have high mechanical strength and reliability. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing a structural relationship between a substrate handler and a semiconductor test system having a test head. 
     FIG. 2 is a diagram showing an example of more detailed structure for connecting the test head of the semiconductor test system to the substrate handler through an interface component. 
     FIG. 3 is a bottom view showing an example of the probe card having an epoxy ring for mounting a plurality of probe contactors in the conventional technology. 
     FIGS. 4A-4E are circuit diagrams showing equivalent circuits of the probe card of FIG.  3 . 
     FIG. 5 is a schematic diagram showing an example of contact structure of the present invention using contactors produced in a horizontal direction on a substrate and vertically mounted on a contactor carrier. 
     FIGS. 6A and 6B are schematic diagrams showing a basic concept of production method of the present invention in which a large number of contactors are formed on a planar surface of a substrate and removed therefrom for later processes. 
     FIGS. 7A and 7B are diagrams showing details of the contactor of the present invention wherein FIG. 7A is a front view of the contactor when no pressure is applied thereto and FIG. 7B is a front view of the contactor when it is pressed against the contact target. 
     FIGS. 8A-8L are schematic diagrams showing an example of production process in the present invention for producing the contactors of the present invention. 
     FIGS. 9A-9D are schematic diagrams showing another example of production process in the present invention for producing the contactors of the present invention. 
     FIGS. 10A-10N are schematic diagrams showing an example of process for producing the contactors of the present invention on the surface of a substrate and transferring the contactors to an intermediate plate. 
     FIGS. 11A and 11B are schematic diagrams showing an example of pick and place mechanism and its process for picking the contactors and placing the same on a contactor carrier to produce the contact structure of the present invention. 
     FIG. 12 is a cross sectional view showing an example of probe contact assembly using the contact structure of the present invention for use between a semiconductor device under test and a test head of a semiconductor test system. 
     FIG. 13 is a cross sectional view showing another example of probe contact assembly using the contact structure of the present invention for use as an interface between the semiconductor device under test and a test head of the semiconductor test system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be explained in detail with reference to FIGS. 5-13. It should be noted that the description of the present invention includes such terms as “horizontal” and “vertical”. The inventors use these terms to describe relative positional relationship of the components associated with the present invention. Therefore, the interpretation of the terms “horizontal” and “vertical” should not be limited to absolute meanings such as an earth horizontal or gravity vertical. 
     FIG. 5 shows an example of contact structure of the present invention. The contact structure is configured by a contactor carrier  20  and contactors  30 . In an application of semiconductor test, the contact structure is positioned, for example, over a semiconductor device such as a silicon wafer  300  to be tested. When the silicon wafer  300  is moved upward, the lower ends of the contactors  30  contact with contact pads  320  on the semiconductor wafer  300  to establish electrical communication therebetween. 
     In this example, the contactor carrier  20  is comprised of a system carrier  22 , a top plate carrier  24 , an intermediate plate carrier  26 , and a bottom plate carrier  28 . The contactor carrier  20  is made of silicon or dielectric material such as polyimide, ceramic or glass. The system carrier  22  supports the top, intermediate, and bottom plate carriers with predetermined space therebetween. The top plate carrier  24 , the intermediate plate carrier  26  and the bottom plate carrier  28  respectively have through holes for mounting the contactors  30 . 
     In FIG. 5, each contactor  30  has a cantilever like shape as a whole which is composed of an upper end (base portion)  33 , a diagonal beam (spring) portion  32 , a straight beam portion  36 , a lower end (contact portion)  35  and a return portion  37 . Preferably, stoppers  34  and  38  are provided to each contactor  30  to securely mount the contactor  30  on the contactor carrier  20 . Namely, the stopper  38  limits the upward movement of the contactor  30  by engaging with the upper plate carrier  24  and the stopper  34  limits the downward movement of the contactor  30  by engaging with the intermediate plate carrier  26 . 
     The diagonal beam portion  32  diagonally extends between the upper end  33  and the straight beam portion  36 . The straight beam portion  36  extends downwardly between the diagonal beam portion  32  and the lower end  35 . The upper end  33  and the lower end  35  function as contact points to establish electrical communication with other components. In the semiconductor test application, the upper end  33  functions to contact with a probe card of the test system and the lower end  35  functions to contact with a contact target such as the contact pad  320  on the semiconductor wafer  300 . 
     The return portion  37  runs upwardly from the lower end  35  in parallel with the straight beam portion  36 . In other words, the return portion  37  and the straight beam portion  36  constitute a space (gap) S therebetween at about a position inserted in the through hole of the bottom plate carrier  28 . This structure ensures a sufficient width with respect to the through holes on the bottom plate carrier  28  and allows flexibility when deforming the contactor  30 . This is effective when the contactor is pressed against the contact target, which will be further explained later with reference to FIGS. 7A and 7B. 
     The contactors  30  are mounted on the contactor carrier  20  via the through holes provided therein. In this example, the top plate carrier  24 , the intermediate plate carrier  26  and the bottom plate carrier  28  respectively include through holes to receive the contactors  30  therein. The upper end  33  is projected from the upper surface of the top plate carrier  24  and the lower end  35  is projected from the lower surface of the bottom plate carrier  28 . The middle portion of the contactor  30  may be loosely coupled to the intermediate plate carrier  26  so that the contactor  30  is movable when the contact structure is pressed against a contact target, such as the contact pad  320  on the semiconductor wafer  300 . 
     The diagonal beam (spring) portion  32  of the contactor  30  functions as a spring to produce a resilient force when the upper end  33  contact the probe card and the lower end  35  is pressed against the contact target. The lower end (contact point)  35  of the contactor  30  is preferably sharpened to be able to scrub the surface of the contact pad  320 . The resilient force promotes such a scrubbing effect at the lower end  35  against the surface of contact pad  320 . The scrubbing effect promotes an improved contact performance when the contact point scrubs the metal oxide surface layer of the contact pad  320  to electrically contact the conductive material of the contact pad  320  under the metal oxide surface layer. 
     FIGS. 6A-6B show basic concepts of the present invention for producing such contactors. In the present invention, as shown in FIG. 6A, the contactors  30  are produced on a planar surface of a substrate  40  in a horizontal direction, i.e., in parallel with a planar surface of the substrate  40 . In other words, the contactors  30  are built in a two dimensional manner on the substrate  40 . Then, the contactors  30  are removed from the substrate  40  to be mounted on the contactor carrier  20  shown in FIG. 5 in a vertical direction, i.e., in a three dimensional manner. Typically, the substrate  40  is a silicon substrate although other dielectric substrates are also feasible. 
     In the example of FIGS. 6A and 6B, as noted above, the contactors  30  are produced on the planar surface of the substrate  40  in the horizontal direction. Then, in FIG. 6B, the contactors  30  are transferred from the substrate  40  to an adhesive member  90 , such as an adhesive tape, adhesive film or adhesive plate (collectively “adhesive tape”). In the further process, the contactors  30  on the adhesive tape  90  are removed therefrom to be mounted on the contactor carrier  20  of FIG. 5 in a vertical direction, i.e., in a three dimensional manner with use, for example, of a pick and place mechanism. 
     FIGS. 7A and 7B show more details of the contactor  30  of the present invention. FIG. 7A is a front view of the contactor  30  when no pressure is provided thereto, and FIG. 7B is a front view of the contactor  30  when the pressure is applied to the contact structure by being pressed against the contact target. FIG. 7A also shows an example of dimensions at each portion of the contactor  30 . As noted above with reference to FIG. 5, the contactor  30  of FIGS. 7A and 7B has the upper end (base portion)  33 , the diagonal beam (spring) portion  32 , the straight beam portion  36 , the lower end (contact portion)  35  and the return portion  37 . The stopper  38  is provided to the upper end  33  and the stopper  34  is provided to the intermediate portion of the contactor  30 . 
     In the semiconductor test application, the upper end  33  contacts with a probe card of the test system such as shown in FIG.  12  and the lower end  35  contacts with the contact target such as a semiconductor wafer under test. When mounted on the contactor carrier  20  of FIG. 5, the upper end  33  is projected from the upper surface of top plate carrier  24  of the contactor carrier  20  and the lower end  35  is projected from the lower surface of bottom plate carrier  28  of the contactor carrier  20 . 
     In the front view of FIG. 7A, the diagonal beam portion  32  and the straight beam portion  36  preferably have a width which is smaller than that of the upper end  33  or the lower end  35  to promote the spring actions. The space (gap) S between the return portion  37  and the straight beam portion  36  further promotes the spring actions as shown in FIG.  7 B. Namely, the space S allows the horizontal movements of the straight beam portion  36  and the diagonal beam portion  32  in the manner shown in FIG.  7 B. Because of the reduced width of the beams portions  32  and  36  and the space S formed at the lower end  35 , the diagonal beam portion  32  and the straight beam portion  36  easily deform when the contactor  30  is pressed between the probe card and the contact target. An example of sizes in the contactor  30  of FIG. 7 is: a=400 μm, b=1100 μm, c=50 μm, d=50 μm, e=140 μm, f=900 μm, and g=1600 μm. 
     FIGS. 8A-8L are schematic diagrams showing an example of production process for producing the contactor  30  of the present invention. In FIG. 8A, a sacrificial layer  42  is formed on a base substrate  40  which is typically a silicon substrate. Other dielectric substrate is also feasible such as a glass substrate and a ceramic substrate. The sacrificial layer  42  is made, for example, of silicon dioxide (SiO 2 ) through a deposition process such as a chemical vapor deposition (CVD). The sacrificial layer  42  is to separate contactors  30  from the silicon substrate in the later stage of the production process. 
     An adhesion promoter layer  44  is formed on the sacrificial layer  42  as shown in FIG. 8B through, for example, an evaporation process. An example of material for the adhesion promoter layer  44  includes chromium (Cr) and titanium (Ti) with a thickness of about 200-1,000 angstrom, for example. The adhesion promoter layer  44  is to facilitate the adhesion of conductive layer  46  of FIG. 8C on the silicon substrate  40 . The conductive layer  46  is made, for example, of copper (Cu) or nickel (Ni), with a thickness of about 1,000-5,000 angstrom, for example. The conductive layer  46  is to establish electrical conductivity for an electroplating process in the later stage. 
     In the next process, a photoresist layer  48  is formed on the conductive layer  46  over which a photo mask  50  is precisely aligned to be exposed with ultraviolet (UV) light as shown in FIG.  8 D. The photo mask  50  shows a two dimensional image of the contactor  30  which will be developed on the photoresist layer  48 . As is well known in the art, positive as well as negative photoresist can be used for this purpose. If a positive acting resist is used, the photoresist covered by the opaque portions of the mask  50  hardens (cure) after the exposure. Examples of photoresist material include Novolak (M-Cresol-formaldehyde), PMMA (Poly Methyl Methacrylate), SU-8 and photo sensitive polyimide. In the development process, the exposed part of the resist can be dissolved and washed away, leaving a photoresist layer  48  of FIG. 8E having an opening or pattern “A”. Thus, the top view of FIG. 8F shows the pattern or opening “A” on the photoresist layer  48  having the image (shape) of the contactor  30 . 
     In the photolithography process in the foregoing, instead of the WV light, it is also possible to expose the photoresist layer  48  with an electron beam or X-rays as is known in the art. Further, it is also possible to directly write the image of the contact structure on the photoresist layer  48  by exposing the photoresist  48  with a direct write electron beam, X-ray or light source (laser). 
     The conductive material such as copper (Cu), nickel (Ni), aluminum (Al), rhodium (Rh), palladium (Pd), tungsten (W) or other metal, nickel-cobalt (NiCo) or other alloy combinations thereof is deposited (electroplated) in the pattern “A” of the photoresist layer  48  to form the contactor  30  as shown in FIG.  8 G. Preferably, a contact material which is different from that of the conductive layer  46  should be used to differentiate etching characteristics from one another as will be described later. The over plated portion of the contactor  30  in FIG. 8G is removed in the grinding (planarizing) process of FIG.  8 H. 
     The above noted process may be repeated for producing contactors having different thickness by forming two or more conductive layers. For example, a certain portion of the contactor  30  may be designed to have a thickness larger than that of the other portions. In such a case, after forming a first layer of the contactors (conductive material), if necessary, the processes of FIGS. 8D-8H will be repeated to form a second layer or further layers on the first layer of the contactors. 
     In the next process, the photoresist layer  48  is removed in a resist stripping process as shown in FIG.  8 I. Typically, the photoresist layer  48  is removed by wet chemical processing. Other examples of stripping are acetone-based stripping and plasma O 2  stripping. In FIG. 8J, the sacrificial layer  42  is etched away so that the contactor  30  is separated from the silicon substrate  40 . Another etching process is conducted so that the adhesion promoter layer  44  and the conductive layer  46  are removed from the contactor  30  as shown in FIG.  8 K. 
     The etching condition can be selected to etch the layers  44  and  46  but not to etch the contactor  30 . In other words, to etch the conductive layer  46  without etching the contactor  30 , as noted above, the conductive material used for the contactor  30  must be different from the material of the conductive layer  46 . Finally, the contactor  30  is separated from any other materials as shown in the perspective view of FIG.  8 L. Although the production process in FIGS. 8A-8L shows only one contactor  30 , in an actual production process, as shown in FIGS. 6A and 6B, a large number of contactors are produced at the same time. 
     FIGS. 9A-9D are schematic diagrams showing an example of production process for producing the contactors of the present invention. In this example, an adhesive tape  90  is incorporated in the production process to transfer the contactors  30  from the silicon substrate  40  to the adhesive tape.  90 . FIGS. 9A-9D only show the latter part of the production process in which the adhesive tape  90  is involved. 
     FIG. 9A shows a process which is equivalent to the process shown in FIG. 8I where the photoresist layer  48  is removed in the resist stripping process. Then, also in the process of FIG. 9A, an adhesive tape  90  is placed on an upper surface of the contactor  30  so that the contactor  30  adheres to the adhesive tape  90 . As noted above with reference to FIG. 6B, within the context of the present invention, the adhesive tape  90  includes other types of adhesive member, such as an adhesive film and adhesive plate, and the like. The adhesive tape  90  also includes any member which attracts the contactor  30  such as a magnetic plate or tape, an electrically charged plate or tape, and the like. 
     In the process shown in FIG. 9B, the sacrificial layer  42  is etched away so that the contactor  30  on the adhesive tape  90  is separated from the silicon substrate  40 . Another etching process is conducted so that the adhesion promoter layer  44  and the conductive layer  46  are removed from the contactor  30  as shown in FIG.  9 C. 
     As noted above, in order to etch the conductive layer  46  without etching the contactor  30 , the conductive material used for the contactor  30  must be different from the material of the conductive layer. Although the production process in FIGS. 9A-9C shows only one contactor, in an actual production process, a large number of contactors are produced at the same time. Thus, a large number of contactors  30  are transferred to the adhesive tape  90  and separated from the silicon substrate and other materials as shown in the top view of FIG.  9 D. 
     FIGS. 10A-10N are schematic diagrams showing a further example of production process for producing the contactor  30  where the contactors are transferred to the adhesive tape. In FIG. 10A, an electroplate seed (conductive) layer  342  is formed on a base substrate  340  which is typically a silicon or glass substrate. The seed layer  342  is made, for example, of copper (Cu) or nickel (Ni), with a thickness of about 1,000-5,000 angstrom, for example. A chrome-inconel layer  344  is formed on the seed layer  342  as shown in FIG. 10B through, for example, a sputtering process. 
     In the next process in FIG. 10C, a conductive substrate  346  is formed on the chrome-inconel layer  344 . The conductive substrate  346  is made, for example, of nickel-cobalt (NiCo) with a thickness of about 100-130 μm. After passivating the conductive substrate  346 , a photoresist layer  348  with a thickness of about 100-120 μm is formed on the conductive substrate  346  in FIG. 10D and a photo mask  350  is precisely aligned so that the photoresist layer  348  is exposed with ultraviolet (UV) light as shown in FIG.  10 E. The photo mask  350  shows a two dimensional image of the contactor  30  which will be developed on the surface of the photoresist layer  348 . 
     In the development process, the exposed part of the resist can be dissolved and washed away, leaving a photoresist layer  348  of FIG. 10F having a plating pattern transferred from the photo mask  350  having the image (shape) of the contactor  30 . In the step of FIG. 10G, contactor material is electroplated in the plating pattern on the photoresist layer  348  with a thickness of about 50-60 μm. An example of the conductive material is nickel-cobalt (NiCo). The nickel-cobalt contactor material will not strongly adhere to the conductive substrate  346  made of nickel-cobalt. 
     In the case where the contactor has two or more different thickness, the above noted process may be repeated for producing the contactor by forming two or more conductive layers. Namely, after forming a first layer of the contactors, if necessary, the processes of FIGS. 10D-10G are repeated to form a second layer or further layers on the first layer of the contactors. 
     In the next process, the photoresist layer  348  is removed in a resist stripping process as shown in FIG.  10 H. In FIG. 10I, the conductive substrate  346  is peeled from the chrome-inconel layer  344  on the substrate  340 . The conductive substrate  346  is a thin substrate on which the contactors  30  are mounted with a relatively weak adhesive strength. The top view of the conductive substrate  346  having the contactors  30  is shown in FIG.  10 J. 
     FIG. 10K shows a process in which an adhesive tape  90  is placed on an upper surface of the contactors  30 . The adhesive strength between the adhesive tape  90  and the contactors  30  is greater than that between the contactors  30  and the conductive substrate  346 . Thus, when the adhesive tape  90  is removed from the conductive substrate  346 , the contactors  30  are transferred from the conductive substrate  346  to the adhesive tape  90  as shown in FIG.  10 L. FIG. 10M shows a top view of the adhesive tape  90  having the contactors  30  thereon and FIG. 10N is a cross sectional view of the adhesive tape  90  having the contactors  30  thereon. 
     FIGS. 11A and 11B are schematic diagrams showing an example of process for picking the contactors  30  from the adhesive tape  90  and placing the contactors on the contactor carrier  20 . The pick and place mechanism of FIGS. 11A and 11B is advantageously applied to the contactors produced by the production process of the present invention described with reference to FIGS. 9A-9D and FIGS. 10A-10N involving the adhesive tape. FIG. 11A is a front view of the pick and place mechanism  80  showing the first half process of the pick and place operation. FIG. 11B is a front view of the pick and place mechanism  80  showing the second half process of the pick and place operation. 
     In this example, the pick and place mechanism  80  is comprised of a transfer mechanism  84  to pick and place the contactors  30 , mobile arms  86  and  87  to allow movements of the transfer mechanism  84  in X, Y and Z directions, tables  81  and  82  whose positions are adjustable in X, Y and Z directions, and a monitor camera  78  having, for example, a CCD image sensor therein. The transfer mechanism  84  includes a suction arm  85  that performs suction (pick operation) and suction release (place operation) operations for the contactors  30 . The suction force is created, for example, by a negative pressure such as vacuum. The suction arm  85  rotates in a predetermined angle such as 90 degrees. 
     In operation, the adhesive tape  90  having the contactors  30  and the contactor carrier  20  having the bonding locations  32  (or through holes) are positioned on the respective tables  81  and  82  on the pick and place mechanism  80 . As shown in FIG. 11A, the transfer mechanism  80  picks the contactor  30  from the adhesive tape  90  by suction force of the suction arm  85 . After picking the contactor  30 , the suction arm  85  rotates by 90 degrees, for example, as shown in FIG.  11 B. Thus, the orientation of the contactor  30  is changed from the horizontal direction to the vertical direction. This orientation change mechanism is just an example, and a person skilled in the art knows that there are many other ways to change the orientation of the contactors. The transfer mechanism  80  then places the contactor  30  on the contactor carrier  20 . The contactor  30  is attached to the contactor carrier  20  when inserted in the through holes. 
     FIG. 12 is a cross sectional view showing an example of total stack-up structure for forming a probe contact assembly using the contact structure of the present invention. The probe contact assembly is used as an interface between the device under test (DUT) and the test head of the semiconductor test system such as shown in FIG.  2 . In this example, the probe contact assembly includes a routing board (probe card)  260 , and a pogo-pin block (frog ring)  130  provided over the contact structure in the order shown in FIG.  12 . 
     The contact structure is configured by a plurality of contactors  30  mounted on the contactor carrier  20 . The upper end (base portion)  33  of each of the contactors  30  is projected at the upper surface of the contactor carrier  20 . The lower end (contact portion)  35  is projected from the lower surface of the contactor carrier  20 . In the present invention, the diagonal beam (spring) portion  32  between the upper end  33  and the intermediate portion has a cantilever shape which is inclined upwardly from the intermediate plate carrier  26 . The contactors  30  may be slightly loosely inserted in the through holes on the contactor carrier  20  in a manner allowing small movements in the vertical and horizontal directions when pressed against the semiconductor wafer  300  and the probe card  260 . 
     The probe card  260 , pogo-pin block  130  and contact structure are mechanically as well as electronically connected with one another, thereby forming a probe contact assembly. Thus, electrical paths are created from the contact point of the contactors  30  to the test head  100  through the cables  124  and performance board  120  (FIG.  2 ). Thus, when the semiconductor wafer  300  and the probe contact assembly are pressed with each other, electrical communication will be established between the DUT (contact pads  320  on the wafer  300 ) and the test system. 
     The pogo-pin block (frog ring)  130  is equivalent to the one shown in FIG. 2 having a large number of pogo-pins to interface between the probe card  260  and the performance board  120 . At upper ends of the pogo-pins, cables  124  such as coaxial cables are connected to transmit signals to printed circuit boards (pin electronics cards)  150  in the test head  100  in FIG.  2  through the performance board  120 . The probe card  260  has a large number of electrodes  262  and  265  on the upper and lower surfaces thereof. 
     When assembled, the base portions  33  of the contactors  30  contact the electrodes  262 . The electrodes  262  and  265  are connected through interconnect traces  263  to fan-out the pitch of the contact structure to meet the pitch of the pogo-pins in the pogo-pin block  130 . Because the contactors  30  are loosely inserted in the through holes of the contactor carrier  20 , the diagonal beam portions  32  of the contactors  30  deform easily and produce resilient contact forces toward the electrodes  262  and the contact pads  320  when pressed against the semiconductor wafer  300 . 
     FIG. 13 is a cross sectional view showing another example of probe contact assembly using the contact structure of the present invention. The probe contact assembly is used as an interface between the device under test (DUT) and the test head such as shown in FIG.  2 . In this example, the probe contact assembly includes a conductive elastomer  250 , a probe card  260 , and a pogo-pin block (frog ring)  130  provided over the contact structure. Since the contactor  30  has the diagonal beam (spring) portion as mentioned above, such a conductive elastomer is usually unnecessary. However, the conductive elastomer may be still useful for compensating the unevenness of the gaps (planarity) between the probe card  260  and the contact structure. 
     The conductive elastomer  250  is provided between the contact structure and the probe card  260 . When assembled, the upper ends  33  of the contactors  30  contact the conductive elastomer  250 . The conductive elastomer  250  is an elastic sheet having a large number of conductive wires in a vertical direction. For example, the conductive elastomer  250  is comprised of a silicon rubber sheet and a multiple rows of metal filaments. The metal filaments (wires) are provided in the vertical direction of FIG. 13, i.e., orthogonal to the horizontal sheet of the conductive elastomer  250 . An example of pitch between the metal filaments is 0.05 mm or less and thickness of the silicon rubber sheet is about 0.2 mm. Such a conductive elastomer is produced by Shin-Etsu Polymer Co. Ltd, Japan, and available in the market. 
     According to the present invention, the contact structure has a very high frequency bandwidth to meet the test requirements of next generation semiconductor technology. Since the large number of contactors are produced at the same time on the substrate without involving manual handling, it is possible to achieve consistent quality, high reliability and long life in the contact performance. 
     Further, because the contactors are assembled on the same substrate material as that of the device under test, it is possible to compensate positional errors caused by temperature changes. Further, it is possible to produce a large number of contactors in a horizontal direction on the silicon substrate by using relatively simple technique. The contact structure produced by the present invention is low cost and high efficiency and has high mechanical strength and reliability. 
     Although only a preferred embodiment is specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and within the purview of the appended claims without departing the spirit and intended scope of the invention.