Abstract:
The present invention provides an apparatus having stacked semiconductor components. Two semiconductor components ( 21, 26 ) are arranged such that their contact regions ( 28, 22 ) are opposite one another. A contact-connection device ( 29 ) forms a short electrical connection between the two contact regions ( 28, 22 ). The contact regions ( 28, 22 ) are connected to external contact regions ( 36 ) of the apparatus via a rewiring ( 23 ).

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a semiconductor apparatus having stacked semiconductor components. The present invention also relates to a method for producing the semiconductor apparatus according to the invention.  
       BACKGROUND ART  
       [0002]     Although the present invention is described with reference to memory components, the invention is not restricted thereto.  
         [0003]     Memory components are connected to one another via a bus system, for example. The wiring paths provided, in particular of the signal lines, should be as short as possible. One technique provides for stacking memory components. The length of the wirings between contacts which are located above one another is kept short in this manner.  FIG. 11  illustrates one known arrangement of housed semiconductor components  5 . Two housed semiconductor components are placed on top of one another and are electrically connected to one another via the external wiring  3 .  FIG. 12  illustrates another arrangement for stacking. In this case, two unhoused semiconductor components  2  are placed on top of one another within a housing and are electrically connected by means of respective internal wiring  1  to the external wiring  3  of the housing.  FIG. 13  illustrates another variant. In this case, two semiconductor components  2  are grouped around an intermediate layer  6  in the apparatus  8  and the individual semiconductor components are once again connected via internal wiring  1  to the external wiring  3  of the housing.  FIG. 14  illustrates a fourth variant which differs from the previous arrangement by virtue of the fact that two semiconductor components  12  are stacked within a housing, an internal wire connection  1  and an interposer substrate forming the connection to the external supply lines, in the form of solder balls  16  in this case.  
         [0004]     The impedance of the wirings between the contact regions  10  of the individual semiconductor components which are connected to one another is disadvantageously not matched in all four of the known semiconductor apparatuses presented. In particular, there is no provision for matching the impedance of the bonding wires having a typical length of the order of magnitude of 1 mm. Future memory generations having signal components in the frequency range of &gt;1 GHz cannot be applied using these bonding wires.  
         [0005]     Another problem results for bus systems having branches in the signal lines. In this case, it is not easily possible to match the impedance of all wiring sections without additional capacitances and inductances. Bus systems therefore always have sections with poor impedance matching.  
         [0006]     This results in the problem of the performance of future memory components being restricted by signal reflections and interference effects on account of the wiring.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to provide a semiconductor apparatus which makes it possible to stack semiconductor components and, at the same time, to provide improved wiring.  
         [0008]     The above object is achieved by means of the apparatus mentioned in Claim  1 . The apparatus is also produced using the method mentioned in Claim  6 .  
         [0009]     The essence of the invention is that two semiconductor components are arranged such that their active surfaces face one another. This results in it being possible to place the contact regions of the respective semiconductor components very close to one another. The fork in the electrical lines to the semiconductor contacts is thus situated in the immediate vicinity of the semiconductor contacts. The length of the wiring sections (which have not been matched) after the fork is therefore negligibly short.  
         [0010]     According to the invention, the signal-carrying wirings are routed at a distance from an earth surface and are isolated from the latter by a dielectric layer. The cross section of the signal wiring, the distance between the signal wirings and the earth surfaces and the dielectric are selected in such a manner that the impedance is optimally matched for the typical frequencies of the semiconductor apparatus.  
         [0011]     In accordance with one development of the apparatus according to the invention, the semiconductor components are embedded in a potting compound or a frame. The potting compound may contain a polymer.  
         [0012]     In accordance with one development of the apparatus according to the invention, the contact-connection device has solder deposits and/or a conductive adhesive.  
         [0013]     The method for producing the apparatus according to the invention achieves the object by virtue of the fact that a semiconductor component is embedded in a potting compound and a rewiring is applied and, in a subsequent step, a second semiconductor component is arranged opposite the first semiconductor component in such a manner that their contact regions are opposite one another and the previously applied rewiring is situated between the two semiconductor components. The two contact regions are connected to one another via a contact-connection device. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Exemplary embodiments will be explained in detail below in conjunction with the figures, in which:  
         [0015]      FIGS. 1-6  show diagrammatic illustrations of one embodiment of the production method;  
         [0016]      FIGS. 7 and 8  show diagrammatic illustrations of a second embodiment of the production method and an impedance-matched semiconductor apparatus;  
         [0017]      FIGS. 9 and 10  show a diagrammatic illustration of a third embodiment of the production method and an impedance-matched semiconductor apparatus; and  
         [0018]      FIGS. 11-14  show diagrammatic illustrations of stacked semiconductor component apparatuses according to the prior art. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     One embodiment of a production method of the present invention is explained in detail in  FIGS. 1-6 . Masking and etching techniques are not described in detail since it is assumed that these techniques are sufficiently well known.  
         [0020]     In a first step (illustrated in  FIG. 1 ), a first semiconductor component  21  is embedded in a potting compound or frame  20 . This potting compound typically comprises a polymer. The first semiconductor component  21  has a contact region  22 . This contact region is situated along a centre line on an active side  25  of the semiconductor component. This active side  25  is not covered by the potting compound  20 . The active surface  25  advantageously forms a plane with an upper surface  24  of the potting compound  20 . In a further step (illustrated in  FIG. 2 ), a rewiring  23  is applied to the first semiconductor component and the potting compound. This rewiring  23  is in contact with the contact-connection region  22  of the first semiconductor component  21 . In the case of a single-row contact arrangement, the rewiring  23  is typically effected along the contact region alternately on the left-hand and right-hand sides. In a subsequent step (illustrated in  FIG. 3 ), an adhesive elevation  27  is applied in a partial region of the first semiconductor component and a contact-connection device  29  is applied to the individual contacts in the contact region  22 . The contact-connection device  29  may have solder deposits and/or conductive adhesive.  
         [0021]     A second semiconductor component  26  with its active surface  30  and the contact-connection region  28  situated therein is subsequently fastened on the adhesive elevations  27 . In this case, the second semiconductor component is oriented in such a manner that its contact-connection region  28  is opposite the contact-connection region  22  of the first semiconductor component. The contact-connection regions  22  of the first semiconductor component are conductively connected to the contact-connection regions  28  of the second semiconductor component by the contact-connection region  28  being brought into contact with the contact-connection device  29  and a permanent connection being established by curing or remelting the contact-connection device  29 . If necessary, a heat-treatment step is carried out in this case in order to liquefy the solder, for example. This results in the rewiring  23  being connected to the two semiconductor components  21 ,  26 . The branch in the rewiring for the two semiconductor components  21 ,  26  is thus situated directly between the two contact-connection regions  22  and  28 . A simple estimation that a signal transmission path which has not been matched has to be shorter than one tenth of the wavelength of the signal in the medium results in a limiting frequency of 200 GHz for this embodiment when the contact regions are at a distance of 100 μm from one another. This makes it possible to communicate very rapidly between the two semiconductor components which are connected via the contact-connection device. It is also ensured that the signal transmission paths from external contacts of the apparatus to the individual semiconductor components are almost of the same length, thus minimizing signal propagation differences.  
         [0022]     In a subsequent step (illustrated in  FIG. 4 ), the carrier substrate of the second semiconductor component can be ground. In this case, it is possible to achieve thicknesses of 50 μm. This is advantageous in order to achieve a low structural height of the semiconductor apparatus.  
         [0023]     In order to achieve mechanical stability of the semiconductor apparatus, the second semiconductor component is embedded in a substrate  34 . This substrate may correspond to the potting compound  20 . Embedding also makes it possible to fill the cavities  33  between the two semiconductor components. A region  35  at the edge of the rewirings is not covered by the substrate  34 . This can be achieved by subsequently removing the substrate or by previously applying a mask and finally removing this mask after the substrate  34  has been applied. The region  35  which is not covered by the substrate  34  is advantageously situated in the vicinity of the edge of the substrate  20 . The external contact-connection regions  36  are thus at a distance from one another, said distance enabling simple installation on a printed circuit board.  FIG. 6  shows that a short rewiring  37  which contact-connects the contact-connection regions  36  situated on a surface of the substrate  34  is deposited onto the region of the rewiring  23  which has not been covered. To this end, the rewiring  37  is patterned.  
         [0024]     The rewiring  37  can be deposited using thin-film and/or thick-film technology, for example electrodeposition and/or deposition in a plasma reaction chamber.  
         [0025]     A diagrammatic illustration of a second embodiment of the present invention is described in  FIG. 7 . After a first semiconductor component  21  has been embedded in the potting compound  20  and a rewiring  23  has been formed, a dielectric layer  40  is deposited. The dielectric layer  40  is configured in such a manner that it does not cover an external region of the rewiring  23  in the region of the potting compound  20 . A conductive layer  41  is deposited onto the dielectric layer. This conductive layer  41  then forms an equipotential surface or an earth surface. In the case of a given electric constant of the dielectric  40  and the typical frequencies of the semiconductor component, the thickness of the dielectric layer  40  and the width of the wiring  23  are selected, in accordance with known techniques or knowledge of electrodynamics, in such a manner that it is possible to match the impedance in an optimum manner.  
         [0026]     In subsequent steps, as described in the first exemplary embodiment, a second semiconductor component is fastened using adhesive elevations on the second semiconductor component or on the dielectric layer. The two contact-connection regions  22  and  28  are electrically connected in turn using a contact-connection device  29 . A substrate  34  is then applied in order to encapsulate the second semiconductor component. A conductive layer  42 , typically comprising a metal, is deposited onto the substrate  34 , said layer constituting an equipotential or earth surface. A dielectric  43  is deposited onto the conductive earth surface  42 . In the final steps, a rewiring  48  is effected, said rewiring connecting the rewiring  23  to the external contact-connection regions situated on an uppermost surface of the dielectric layer  43 . The impedance of the second rewiring  48  is matched using the second earth surface  42  and the dielectric layer  43  lying in between. The advantage of this embodiment resides in the fact that impedance matching is essentially ensured from the external contact connection  36  to the branch in the rewiring  23  in the immediate vicinity of the contact-connection regions  22  and  28 .  
         [0027]      FIGS. 9 and 10  illustrate a third embodiment of the present invention. This embodiment differs from the second embodiment by virtue of the fact that an equipotential or earth surface  45  is applied to the first embedded semiconductor component  21  in a first step. This earth surface  45  does not touch the contact-connection region  22 . A dielectric layer  40  is deposited onto the earth surface  45 . A rewiring  44  is then formed. This rewiring contact-connects the contact-connection region  22 . The impedance of this rewiring is matched using the earth surface  45  and the dielectric layer  40 . The subsequent steps for producing the third embodiment of the present invention correspond to those of the second embodiment.  
         [0028]     Although the present invention was described with reference to preferred exemplary embodiments, it is not restricted thereto. In particular, various techniques are known in order to fasten the second semiconductor component on the first semiconductor component. Furthermore, the materials for the rewiring are not restricted to metals but may likewise comprise doped semiconductor materials.