Abstract:
A contacting device comprises a carrier device with a first surface, a plurality of first terminal regions on the first surface, at least one elastic elevation on the first surface, and a plurality of interconnects, each running from a respective of the first terminal regions to an upper side of the elastic elevation. The plurality of first terminal regions is configured so that signals of a tester device can be fed to the plurality of first terminal regions, the interconnects have first contact regions located at the upper side of the elastic elevation configured to be contacted electrically with corresponding second contact regions of an integrated circuit, and the first contact regions comprise first particles for roughening the surface of the first contact regions.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a contacting device for the contacting of an integrated circuit, in particular of a chip or a wafer, with a tester device, a corresponding testing method and a corresponding production method.  
         [0003]     Although it can be applied in principle to any integrated circuits or components, the present invention and the problem on which it is based are explained with reference to chips with integrated circuits using silicon technology.  
         [0004]     2. Description of the Prior Art  
         [0005]     The increasing production density of today&#39;s electronic circuits or electronic circuit units, also referred to as chips, is leading to increased requirements for testing. Before delivery, the electronic circuit units must be subjected to various tests. In a conventional way, the electronic circuit units accommodated in packages are inserted into special test sockets and thereby contacted at the package contacts. For the contacting of unpackaged chips, needle cards, which usually have resilient contact pins, are used.  
         [0006]     During the contacting, the circuit units to be tested are subjected to various test conditions. For example, series of tests are conducted at an elevated temperature over a prolonged period of time, for example 120° C. for a time period of 24 hours. These series of tests are also referred to as “burn-in”. Long test times can rapidly lead here to high costs of testing and to commercial disadvantages.  
         [0007]     For the efficient contacting of the circuit units to be tested, it has been proposed to provide sockets into which the circuit units to be tested are introduced.  
         [0008]     A major disadvantage of known methods for the contacting of electronic circuit units is that these circuit units have to be provided with a package and corresponding terminal contacts outside the package.  
         [0009]     Conventional contacting devices cannot be used for circuit units to be tested without a package, i.e. so-called “bare chips”. There is an increasing demand for provision of so-called multi-chip modules, i.e. various chips or circuit units are accommodated in a single module.  
         [0010]     It is quite possible here for the individual circuit units to be supplied by different manufacturers. One important aspect in the delivery of circuit units without a package is that the circuit units must be inspected for defects just as carefully as the packaged circuit units.  
         [0011]     Most widespread are chips with contact areas of aluminum. An electrical measurement of such unpackaged chips is currently carried out with needle adaptors. The needles perforate the thin oxide skin of the aluminum and lead to a good, low-impedance contact. Corresponding measuring devices are complex, expensive and unsuitable for a multi-hour burn-in. Published German patent application 103 24 450 A1 discloses an example of a known contacting device.  
       SUMMARY OF THE INVENTION  
       [0012]     It is an object of the present invention to provide an improved contacting device for the contacting of an integrated circuit, in particular of a chip or a wafer, with a tester device, a corresponding testing method and a corresponding production method, which ensure a more reliable low-impedance temporary electrical contact even in the case of contact metals with a thin surface oxide which is also suitable for a burn-in.  
         [0013]     The object is achieved in accordance with the invention by means of a contacting device for the contacting of an integrated circuit with a tester device, comprising a carrier device with a first surface, a plurality of first terminal regions on the first surface, to which signals of the tester device can be fed; at least one elastic elevation on the surface; and a plurality of interconnects, which respectively run from a first terminal region to the upper side of the elastic elevation; wherein the regions of the interconnects form on the upper side of the elastic elevation first contact regions, which can be brought into electrical contact with corresponding contact regions of the integrated circuit, and the interconnects are roughened, at least in the regions, by particles for roughening the surface being incorporated in the regions.  
         [0014]     The idea on which the present invention is based is to use a contact system in which the ends of the contact elements of the integrated circuit and the substrate are placed one on top of the other and are simultaneously under a certain compressive pressure, the interconnects being roughened at least in the contact regions, so that a thin oxide on contact regions of the integrated circuit can be easily perforated.  
         [0015]     The contact surfaces of the contact structures on both sides should be of such a nature that they are stable over a long time with regard to the pressure contact and have good electrical functionality. It must also be ensured that the material of the elastic elevations retains the desired elasticity in the entire application range.  
         [0016]     The inventive elastic contact structure makes it possible to compensate for differences between the materials involved in the linear expansion in the connecting plane, and also to ensure a reliable electrical contact between the materials involved in the direction of compression.  
         [0017]     The inventive contacting devices can be produced at very low cost and are suitable for contacting contact areas with a thin oxide reliably and with low impedance. The contact elements are temperature-resistant up to at least 150° C. and consequently also suitable for burn-in processes of memory chips.  
         [0018]     The elastic elevation may be comprised of an elastomer, particles for roughening the surface of the elastic elevation being incorporated or applied and that this roughening is molded into the regions.  
         [0019]     The particles for roughening the surface may be incorporated in the regions, protuberances for roughening the surface may be incorporated in the regions, the particles may have a grain size in the range of 3 to 20 μm, the interconnects may be produced from copper, the interconnects may be coated with nickel and finally with hard gold, the at least one elastic elevation may have an elongate wall-like form, at least two elastic elevations may be provided, running substantially parallel to each other, and a plurality of second terminal regions may be provided on a second surface, to which signals of the tester device can be fed, the first and second terminal regions being connected to each other by means of via holes.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a schematic representation of an exemplary embodiment of an inventive contacting device.  
         [0021]      FIGS. 2   a,b  are cross-sectional views of elastic contact elements of a known contacting device as described in published German patent application 103 24 450 A1 along the line A-A′ in  FIG. 1 .  
         [0022]      FIG. 3  is a cross-sectional view of an elastic contact element of an contacting device according to the first embodiment of the present invention along the line A-A′ in  FIG. 1 .  
         [0023]      FIG. 4  is a cross-sectional view of an elastic contact element of a contacting device according to a second embodiment of the present invention along the line A-A′ in  FIG. 1 .  
         [0024]      FIG. 5  is a cross-sectional view of an elastic contact element of a contacting device according to a third embodiment of the present invention along the line A-A′ in  FIG. 1 .  
         [0025]      FIG. 6  is a cross-sectional view of two elastic contact elements of the contacting device according to a fourth embodiment of the present invention along the line A-A′ in  FIG. 1  with a chip placed on and pressed into place for testing. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     In the figures, the same reference numerals designate components which are the same or functionally the same.  
         [0027]     Without restricting generality, in the two exemplary embodiments explained below the integrated circuit is a chip.  
         [0028]      FIG. 1  is a schematic representation of a contacting device according to a first embodiment of the present invention.  
         [0029]     In  FIG. 1 , reference numeral  10  designates a carrier device of an organic material or of silicon or a ceramic, which has a rectangular form and a first, upper surface  10   a  and a second, lower surface  1   b.    
         [0030]     On the upper surface  10   a  there are two elastic elevations  15 ,  15 ′ of an elastomer, such as for example silicone, polyurethane or flexibilized epoxy. The elastic elevations have an elongate, wall-shaped form and follow in their shape the contact areas to be contacted of the chip to be tested. They may be applied, for example, by a printing process or by dispensing.  
         [0031]     A plurality of first terminal regions  45  are provided on a first surface  10   a , to be precise in respective rows parallel to the first and second elastic elevations  15 ,  15 ′. Starting from the first terminal regions  45 , interconnects  55 ′ run to the upper side OS and OS′, respectively, of the elastic elevations  15 ,  15 ′.  
         [0032]     The end regions  60  of the interconnects  55 ′ form on the upper sides OS and OS′, respectively, of the elastic elevations  15 ,  15 ′ first contact regions, which can be brought into electrical contact with corresponding contact regions  2 ,  2 ′ of the integrated circuit  1  (compare  FIG. 6 ). As a result of how they are produced, the interconnects  55 ′ are roughened in such a way that, in the regions  60 , a thin oxide on contact regions  2 ,  2 ′ of the integrated circuit  1  can be perforated when pressure is applied, so that a secure low-impedance contact is possible even in the case of slightly corroded contact areas of the integrated circuit  1 .  
         [0033]     The first terminal regions  45  are connected by means of via holes  50  to second terminal regions  40 , which are provided on the second surface  10   b  of the carrier device  10 .  
         [0034]     By means of further connections that are not represented any more specifically, the second terminal regions  40  are connected to a tester device  400 , which applies to the regions  60  predeterminable electrical signals, which are to be transferred to the chip  1  to be tested.  
         [0035]     The interconnects  55 ′, mounted elastically on the elastic elevations  15 ,  15 ′, are arranged in such a way that a contact region  2 ,  2 ′ of the chip corresponds to each region  60 . With its contact areas adjusted, the chip is placed onto the contacting device formed in this way and is pressed into place by means of pressure P, as represented in  FIG. 6 .  
         [0036]      FIGS. 2   a,b  are cross-sectional views of elastic contact elements of the known contacting device according to DE 103 24 450 A1 along the line A-A′ in  FIG. 1 .  
         [0037]      FIG. 2   a  shows the elastic elevation  15 ′ of the elastomer directly after its production by dispensing.  
         [0038]      FIG. 2   b  shows the elastic elevation  15 ′ after an interconnect  55  comprising the layer construction of copper, nickel and hard gold has been applied to its upper side OS′ in an electrodepositing process. The contact area to be contacted of the electrical circuit, which is produced from aluminum, has a thin oxide film. Tests have shown that low-impedance contacting for electrical testing or burn-in is not possible with such a known contacting device.  
         [0039]      FIG. 3  is a cross-sectional view of an elastic contact element of a contacting device according to a first embodiment of the present invention along the line A-A′ in  FIG. 1 . In the case of the embodiment shown in  FIG. 3 , particles  65 ′—for example silicon oxide—are embedded in the elastomer of the elastic elevation  50 ′. The particles  65 ′ are sharp-edged and preferably much harder than aluminum. The grain size and the grain size distribution depend on the size of the contact areas to be contacted of the integrated circuit and typically lie in the range from 3 to 20 μm. The particles  65 ′ located at the surface provide the roughness of the interconnect  55 ′ deposited over them, since, given an appropriately chosen thickness of the interconnect  55 ′, their contours are molded onto the latter.  
         [0040]      FIG. 4  is a cross-sectional view of an elastic contact element of a contacting device according to a second embodiment of the present invention along the line A-A′ in  FIG. 1 .  
         [0041]     As shown in the embodiment according to  FIG. 4 , it is sufficient if such particles  65 ″ are merely provided on the surface of the elastic elevation  15 ′.  
         [0042]     The particles  65 ′ according to  FIG. 3  may be mixed into the elastomer before processing. The particles  65 ″ according to  FIG. 4  are applied to the non-cured elastomer surface after processing and remain adhesively attached therein.  
         [0043]     The particles  65 ′ and  65 ″, incorporated in or applied to the elastomer of the elastic elevation  15 ′ according to  FIG. 3  and  FIG. 4 , respectively, are, as mentioned above, molded by the interconnects  55 ′ and  55 ″, respectively, and consequently produce in the regions  60  very rough surfaces, which lead to reliable and low-impedance contacting of oxidized contact areas of the integrated circuit  2 ,  2 ′ of the chip  1 . Hard gold preferably comes into consideration as the final covering material of the interconnects  55 ′ and  55 ″. This would have the advantage that no oxide can form in the regions  60  in the first place and only the oxide of the chip contact areas has to be perforated.  
         [0044]      FIG. 5  is a cross-sectional view of an elastic contact element of a contacting device according to a third embodiment of the present invention along the line A-A′ in  FIG. 1 .  
         [0045]     In the case of the embodiment according to  FIG. 5 , particles  65 ′″ are integrated in the interconnect  55 ′″ and not in the elastic elevation  15 ′. This may take place by embedding non-conducting or conducting particles  65 ′″ in an electrodepositing process. Such dispersive, electrolytic depositing is also used for example in the production of grinding wheels. As an alternative to this, the embedding of such particles  65 ′″ by a currentless depositing process is also possible. When non-conducting particles  65 ′″ are used, they must be completely embedded; conducting particles  65 ′″ may also be only partially embedded.  
         [0046]      FIG. 6  is a cross-sectional view of two elastic contact elements of the contacting device according to a fourth embodiment of the present invention along the line A-A′ in  FIG. 1  with the chip placed on and pressed into place for testing.  
         [0047]     In the case of the embodiment shown in  FIG. 6 , also represented in addition to the steps of the elastic elevations  15 ,  15 ′, is a semiconductor chip  1  with contact regions  2 ,  2 ′ of aluminum, which is pressed under pressure P onto the region  60  in such a way that the rough surface of the interconnects  554 ′ perforates a thin aluminum oxide on the contact regions  2 ,  2 ′, and consequently provides a reliable electrical contact.  
         [0048]     A further special feature in the case of this embodiment is that the roughness of the interconnects  55 ″″ is achieved in the region  60  by protuberances  65 ″″, which can be realized by choosing the depositing parameters of the state of the bath in such a way that an incomplete protuberance-like deposition takes place. Such an incomplete protuberance-like deposition may take place, for example, by depositing hard gold on the elastic elevation  15 ,  15 ′ or an interconnect of copper provided under it. High current densities and non-use of wetting agents in the bath promote such irregular electrodepositing. There are also analogous possibilities in the case of currentless depositing.  
         [0049]     Although the present invention has been described above on the basis of preferred exemplary embodiments, it is not restricted to these but can be modified in various ways.  
         [0050]     The present invention can in particular be applied not only to chips, but also to hybrids, wafers or other unpackaged integrated circuits or even more generally to components with terminals of superficially oxidizing materials.