Abstract:
A method and a device for the mutual contacting of two wafer-type component composite configurations made of multiple identical components which are implemented coherently, in particular a semiconductor wafer ( 12 ) with a functional component wafer ( 14 ), to produce electronic assemblies on the wafer level, in which the component composite configurations are each situated on a receptacle unit ( 11; 13 ) and the contact pressure necessary for the contacting between contact metallizations of the component composite configurations to be connected to one another is generated in such a way that a vacuum is generated in a contact chamber which receives the component composite configurations and is delimited by the receptacle units, and the contacting of the contact metallizations is performed by a rear energy impingement of a component composite configuration.

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS 
     This is a National Phase of International Application No. PCT/DE2005/001230, filed on Jul. 11, 2005, which claims priority from German Patent Application No. 10 2004 034 421.3, filed on Jul. 15, 2004. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method for the mutual contacting of two wafer-type component composite configurations from multiple identical components which are implemented coherently, in particular a semiconductor wafer with a functional component wafer, to produce electronic assemblies on the wafer level, according to Claim  1 . In addition, the present invention relates to a device according to Claim  7 , which is especially suitable for performing the method. 
     The method and the device of the above-mentioned type are very generally used when substrates implemented coherently in a composite are to be connected with components also situated in a composite without prior dissolution of the particular composite. 
     To produce electronic assemblies on the chip level, for example, chips which are contacted with functional components activated via the chips, such as laser diodes, it is known to produce both the chip and also the laser diode on the wafer level, i.e., in a coherent wafer composite, and subsequently to isolate both the chips and also the laser diodes from the particular wafer composite before contacting the chips with the laser diodes. The necessity results therefrom of performing a positioning and connection procedure necessary for contacting the chips with the laser diodes separately and repeatedly in accordance with the number of chips and/or laser diodes. 
     The advantages of being able to perform contacting of this type on the wafer level in order to perform the required positioning and connection procedure only once for multiple laser diodes or chips situated in the composite are obvious. Because of the relatively large-area distribution of the individual contact metallizations of chips and laser diodes to be connected to one another, it has proven difficult, however, to set a uniform gap dimension over the entire wafer surface. The result thereof may be faulty contacts between individual pairs of contact metallizations. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to suggest a method and a device for producing electronic assemblies on the wafer level which allows the implementation of a uniform gap dimension between the wafers to be contacted. 
     To achieve this object, the method according to the present invention has the features of Claim  1  and the device according to the present invention has the features of Claim  7 . 
     In the method according to the present invention, the contact pressure between the contact metallizations to be connected to one another which is required for the contacting is generated by implementing a vacuum in the contact chamber receiving the component composite configurations. The subsequent contacting of the contact metallizations occurs through a rear energy impingement of a component composite configuration. 
     Implementing the vacuum in the contact chamber ensures a coplanar configuration of the component composite configurations, without the specific bending behavior of the wafers and/or of devices on which the wafers are situated having to be taken into consideration in comparison with a pressure impingement for generating the required contact pressure. 
     In particular, it is not necessary to take measures to compensate for the bending behavior and/or a deviation of the bending line from a straight line in the wafers, as would be the case in the event of a pressure impingement of the wafers. 
     Furthermore, arbitrarily high contact pressures between the wafers, which are solely limited by the component strength, may be set via the setting of the vacuum, without an additional outlay for apparatus in terms of mechanical or hydraulic contact pressure devices being necessary. 
     The method according to the present invention may be used especially advantageously for producing “SAW (surface acoustic wave) filters” on the wafer level. In these assemblies, to achieve a vacuum-tight connection with carrier chips, cover chips are connected to the carrier chips via a hermetically-sealed peripheral contact metallization in addition to the electrical contacts. 
     In an especially advantageous variation of the method, the contact chamber is generated by producing a vacuum-tight connection between the receptacle units which receive the component composite configurations having their contact metallizations diametrically opposite one another. It is thus possible to implement the contact chamber using the lowest possible number of components, only a seal unit being added to the receptacle units provided in any case. 
     Energy impingement of the friction-locked composite of the component composite configurations implemented by the vacuum impingement in the contact chamber prior to the thermal contact, i.e., to implement the bond connection, is made possible in an especially simple method by an energy impingement of the composite via a receptacle unit. In this way, the outlay for apparatus required for performing the method may especially be reduced, since a furnace unit, into which the composite situated in the contact chamber would be introduced, may be dispensed with. 
     An especially simple type of energy impingement may be performed by performing the energy impingement by implementing the receptacle unit as a heating unit. 
     Alternatively, it is possible to perform the energy impingement by a contact heating of the receptacle unit, so that the receptacle unit is solely used for introducing heat into the composite of the component composite configurations provided in the contact chamber. 
     In a further advantageous embodiment of the method, the energy impingement is performed by a radiation impingement of the receptacle unit. It is advantageously possible for this purpose to tailor the material of the receptacle unit and the type of the radiation source to one another so that, for example, if an absorbent material is selected for the receptacle unit, an infrared radiation source may be used, or if an optically transparent material is selected for the receptacle unit, a laser radiation source may be used. 
     The device according to the present invention has a first receptacle unit for receiving the first component composite configuration and a second receptacle unit for receiving the second component composite configuration, a seal unit for the sealed connection of the receptacle units to one another and for implementing a pressure-tight contact chamber which encloses the component composite configurations, an attachment unit for attaching a vacuum unit to the contact chamber, and an energy impingement unit for the rear energy impingement of at least one component composite configuration via a receptacle unit. Accordingly, in the device according to the present invention, the contact chamber required for generating a vacuum acting between the component composite configurations is made possible by the sealed connection of the receptacle units to one another. 
     It has been shown to be especially advantageous if the seal unit is implemented as elastic at least in a connection area between the receptacle units. This elasticity may be achieved both by a corresponding material selection for the seal unit and also by a dimensionally-elastic design of the seal unit. It is essential for this purpose that the seal unit allows the implementation of the vacuum-tight contact chamber, and, in addition, does not obstruct the implementation of the contact pressure between the contact metallizations of the component composite configurations, which are situated diametrically opposite one another. 
     According to an advantageous embodiment, the seal unit has a seal body having a seal surface formed by a rigid body unit. It is thus possible to implement the elasticity required for the function of the device and, in addition, to allow a design of the seal surface which has proven in operation to be as free from abrasion as possible. 
     If the rigid body unit comprises a sealing ring which peripherally encloses the first receptacle unit and is connected to this receptacle unit, whose sealing face presses flatly against the second receptacle unit, a secure seal may be implemented, and, in addition, a deviation in the parallelism between the receptacle units may easily be compensated for via the seal body. 
     An embodiment of the device having a seal body which does not impair the usable area of the receptacle unit for situating the component composite configuration is possible if the seal body is formed from a material web of an elastic, gas-tight material and is connected to the circumference of the receptacle unit. 
     A sealed connection between the seal body and the receptacle unit may be dispensed with if the seal body extends over the rear of the receptacle unit and thus encloses the rear of the receptacle unit. 
     If the receptacle unit is provided with a handling unit, with an elastic equalizing unit situated interposed, it is ensured that parallelism deviations between the handling unit and the receptacle unit do not have a disadvantageous effect on the contact pressure between the component composite configurations. 
     An especially compact embodiment of the device is possible if the second receptacle unit is implemented as a contact plate for contact heating using a contact heating unit to implement an energy impingement unit, since the device may thus be implemented independently of a heating unit and is solely to be brought into contact with a heating unit for the heat impingement of the component composite configuration. 
     Alternatively, it is possible to implement the second receptacle unit as a plate which is at least regionally radiation-transparent to implement an energy impingement unit. 
     An embodiment of the device which is compact overall, having a quasi-integrated heating unit, is made possible if the second receptacle unit is implemented as a contact heater to implement an energy impingement unit. 
     An embodiment of the receptacle unit as a contact heater which is especially simple to implement comprises an embodiment of the receptacle unit as a resistance heater. 
     If the receptacle unit implemented as a resistance heater is implemented as an electrical resistance film, an especially light weight and simultaneously rapidly acting heating possibility for the component composite configuration results. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, preferred variations of the method are described in greater detail with explanation of preferred embodiments of the devices used for this purpose on the basis of the drawing in which 
         FIG. 1  shows a wafer bonding device for producing a contact composite between two wafers which are each situated on a receptacle unit, 
         FIG. 2  shows the wafer bonding device having the wafer composite produced in a contact chamber; 
         FIG. 3  shows the wafer bonding device raised from a work platform while carrying along the wafer composite; 
         FIG. 4  shows the wafer bonding device having the wafer composite before the positioning on a contact heater; 
         FIG. 5  shows the wafer bonding device positioned on the contact heater for performing the bond connection between contact metallizations of the wafer; 
         FIG. 6  shows a performance of the bond connection using laser impingement; 
         FIG. 7  shows a performance of the bond connection using a receptacle unit implemented as a resistance film. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a wafer bonding device  10  having a first receptacle unit  11  for situating a first wafer  12  and a second receptacle unit  13  for situating a second wafer  14 . In the present case the receptacle unit  11  comprises a metal plate and is connected to a handling unit  17  with a flat elastic seal body  15 , formed here from a film web, of a seal unit  15  and an intermediate layer  16  having elastically springy properties being situated interposed. The handling unit  17  is provided with a control unit  18  acting in three axes, which allows spatial positioning of the wafer  12  situated on the receptacle unit  11  in relation to the wafer  14  situated on the receptacle unit  13 . 
     As  FIG. 1  also shows, the receptacle unit  13  is situated on a work platform  48 , which is located in the present case on a base frame  20 , with an elastic support unit  19  situated interposed. 
     As  FIG. 1  also shows, both the receptacle unit  11  connected to the handling unit  17  and also the receptacle unit  13  situated on the work platform  48  are provided with an attachment unit  21  or  22 , respectively, for attachment to a vacuum pump in each case (not shown in greater detail here). To implement the attachment unit  21 , the receptacle unit  11  has a hole  23 , which is situated aligned with a hole  24  in the seal body  15 , a hole  25  in the intermediate layer  16 , and a hole  26  in the handling unit  17 . The receptacle unit  13  has a hole  27 , which passes into a channel  28  implemented in the work platform  48 . The external hole  26  in the handling unit  17  and the channel  28  in the work platform  48  are each provided for the attachment to the vacuum pumps (not shown). 
     The handling module made of the handling unit  17  and the receptacle unit  11  connected thereto with the seal unit  29  and the intermediate layer  16  situated interposed, which is shown in  FIG. 1  above and at a distance to the receptacle unit  13  and the wafer  14  situated thereon, is to be identified in the following as a bonding head  30 . The bonding head  30  has a further attachment unit  31  for attachment to a further vacuum pump (not shown in greater detail here), which allows the external attachment of the vacuum pump via a hole  32  in the receptacle unit  11 , a hole  33  in the seal body  15 , a hole  34  in the intermediate layer  16 , and a hole  35  in the handling unit  17 . 
     In a method for producing a bond connection between the two wafers  12 ,  14 ,  FIG. 1  shows a phase directly before the mutual contacting of contact metallizations of the wafers  12 ,  14 , which contact metallizations are not shown in greater detail here and are diametrically opposite one another on contact surfaces  43 ,  44 . The phase illustrated in  FIG. 1  is preceded by reception of the wafer  12  by the bonding head  30  by a vacuum impingement of the wafer  12  via the bonding head  30  positioned above the wafer  12  and positioning of the bonding head  30  above the wafer  14 , which was previously positioned on the work platform  48  and is also fixed on the receptacle unit  13  using vacuum impingement. 
     In the phase illustrated in  FIG. 1 , a relative orientation of the bonding head  30  then occurs in relation to the work platform  48  in such a way that the contact metallizations of the wafers  12 ,  14  to be contacted with one another are brought into an overlapping position. For this purpose, the bonding head  30  is activated via the control unit  18  as a function of an image processing unit (not described in greater detail here), whose input signals originate from a camera unit  36  situated in a wafer intermediate chamber  48 . 
     After setting the overlapping position between the contact metallizations of the wafers  12 ,  14  and removing the camera unit  36  from the wafer intermediate chamber  49 , the bonding head  30  travels toward the work platform  48  until reaching a mechanical contact between the contact metallizations of the wafers  12  and  14  to be contacted with one another. Upon reaching the contact, a seal ring  37  of the seal unit  29 , which is shown in  FIG. 2  and is connected gas-tight to the seal body  15 , has its circular sealing surface  38  pressed against the receptacle unit  13 , which is formed by a steel plate in the exemplary embodiment illustrated here and is situated on the work platform  48 . In the exemplary embodiment illustrated here, the seal ring  37  comprises two metal rings  39 ,  40 , which receive the peripheral edge of the seal body  15  between them. 
     In the configuration illustrated in  FIG. 2 , a contact chamber  41  which is delimited by the receptacle units  11 ,  13  and is sealed by the seal unit  29  is formed by the contact of the seal ring  37  with the receptacle unit  13 , which contact chamber receives a wafer composite  42  formed by the wafers  12  and  14  therein. After the contact chamber  41  illustrated in  FIG. 2  is implemented, it may be evacuated via the attachment unit  31  which is implemented in the bonding head  30  and discharges via the receptacle unit  13  into the contact chamber  41 . 
     By implementing the vacuum in the contact chamber  41 , the wafers  12 ,  14  of the wafer composite  42  are pressed against one another, so that depending on the level of the vacuum set, the contact pressure required for the a subsequent thermal connection procedure between the contact metallizations may be set. If parallelism deviations exist between the surfaces of the receptacle units  11 ,  13 , these are compensated for by the elastic intermediate layer  16  situated between the receptacle unit  11  and/or the seal body  15  of the seal unit  29  and the handling unit  17 , so that in any case a coplanar configuration of the contact surfaces  43 ,  44  of the wafers  12 ,  14  and/or the implementation of a constant gap dimension over the contact surfaces between the wafers  12 ,  14  in the wafer composite  42  is ensured. 
     After setting the desired contact pressure between the wafers  12 ,  14  of the wafer composite  42  in the contact chamber  41 , the vacuum applied to the rear of the wafer  14  via the attachment unit  22  implemented in the work platform  48  is turned off, so that, as shown in  FIG. 3 , the bonding head  30 , together with the receptacle unit  13 , may be lifted off of the work platform  48  while maintaining the wafer composite  42  implemented in the contact chamber  41 . 
     As shown in  FIGS. 4 and 5 , the bonding head  30  is subsequently positioned over a preheated contact heating unit  45  and lowered thereon, so that the receptacle unit  13  is lowered onto the contact heating unit  45  to allow a heat transfer. A heating procedure to the desired bonding temperature is now performed in accordance with the desired temperature profile, for the monitoring of which a temperature sensor (not shown in greater detail here) may be provided in the receptacle unit  11  of the bonding head  30 . If maintaining the bonding temperature over a defined duration is intended, the configuration illustrated in  FIG. 5  may also be provided with a distance regulation unit (not shown in greater detail here), which, after reaching the bonding temperature, allows the setting and/or changing of a distance between the receptacle unit  13  and a contact surface  46  of the contact heating unit  45  to maintain the bonding temperature over a specific duration. 
     As an alternative to the positioning of the bonding head  30  on the contact heating unit  45  explained above, it is also possible to implement the work platform  48  shown in  FIG. 1  as heated and to perform the contact heating in the configuration illustrated in  FIG. 1 . 
     If targeted cooling is desired, cooling may subsequently be performed by positioning the bonding head  30  on a contact cooling unit (not shown in greater detail here). 
     In addition, it is also possible to cool the bonding head  30  using a coolant flow, in particular an air flow, conducted through the vacuum channel  26  or separate cooling channels. 
     To prevent a parallelism deviation between the contact surface  46  of the contact heating unit  45  and the receptacle unit  13  from having an effect on the wafer composite  42 , as shown in  FIGS. 4 and 5 , an elastic support unit  19  may be provided between the base frame  20  and the contact heating unit  45 , similarly as in the configuration shown in  FIGS. 1 through 3 . 
     During the bonding phase illustrated as an example in  FIG. 5 , in which thermal bonding between the contact metallizations of the wafers  12  and  14  occurs, it is also possible if necessary to elevate the contact pressure generated by the vacuum in the contact chamber  41  further by a pressure impingement of the wafer composite  42  using the bonding head. The vacuum fixing of the wafers  12  and  14  against one another prevents a sliding movement of the wafers  12 ,  14  on one another which would otherwise be possible due to the pressure impingement. 
     Alternative possibilities for heating the wafer composite  42  situated in the contact chamber  41  on the bonding head  30  are illustrated in  FIGS. 6 and 7 .  FIG. 6  shows heating using a selective energy impingement of the contact metallizations via a pivotable laser emission unit  47 , a receptacle unit  50  made of a material transparent to the laser radiation being implemented for this purpose. If the receptacle unit is implemented from a material which absorbs radiation and/or heat, such as silicon, the wafer composite may be heated using heat conduction. 
     In a further embodiment of the bonding head (not shown in greater detail here), it may also be provided with an integrated laser emission unit, so that notwithstanding the exemplary embodiment illustrated in  FIG. 6 , the heating of the wafer composite is performed via the receptacle unit facing toward the bonding head. 
       FIG. 7  shows a receptacle unit  51  which is situated on the bonding head  30  and is implemented as an electrically heatable resistance film. A receptacle unit directly heatable in this way allows the production of the thermal bond connection between the contact metallizations of the wafers  12 ,  14  of the wafer composite  42  on the bonding head  30  itself, without a separate heating unit having to be provided.