Abstract:
Methods of assembling an integrated circuit are provided. An interposer supported by an integrated handler is solder bumped onto one or more bond pads on a substrate. The integrated handler is removed from the interposer. A side of the interposer opposite that of the substrate is solder bumped to one or more bond pads on a chip.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to the field of integrated circuits and, more particularly, to assembly operations performed on an integrated circuit for packaging. 
       BACKGROUND OF THE INVENTION 
       [0002]    As the complexity of integrated circuit technology increases, requiring an increased number of linked transistors, the integrated circuitry dimensions are shrinking. Thus, a specific challenge in the semiconductor industry is to develop improved methods for electrically connecting and packaging circuit devices. Such improvements may include the construction of transistors which occupy less surface area on the silicon chip/die for the semiconductor industry. 
         [0003]    The decreasing size of integrated circuit (IC) packages and increasing size and level of circuit integration in the IC packages is particularly true in the case of system-on-a-chip (SoC) devices. Most, if not all, of an electronic appliance of SoC devices is integrated onto a single integrated circuit (IC) die. However, as the number and complexity of devices increase, it becomes more and more important to pack as many IC dies as possible onto circuit board. Meanwhile, miniaturization of systems is desired for most electronic applications. In order to further these objectives, manufactures place IC dies as close together as possible on a substrate to increase IC die density and reduce the interconnection distance between IC dies. The ultimate solution is to stack IC dies vertically in order to minimize the signal delay. Conventional chip stacking involves wire bonding, which has relatively low interconnection density and lager electrical parasitics. Die stacking with area array interconnection can maximize the interconnection density and minimize interconnection distance, thus improve the overall performance a system of the integrated circuit dies. 
         [0004]    Stacking of multiple levels of integrated circuit dies with area array interconnects requires careful design of bonding metallurgy hierarchy and assembly processes. In addition, the stacked integrated circuit dies are usually thinned significantly to ensure small total thickness for the packages. Therefore, novel assembly method and apparatus are needed to facilitate the bumping and stacking of the fragile thin Si dies. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention in an illustrative embodiment provides techniques for assembling integrated circuit devices using a thin silicon (Si) interposer. 
         [0006]    In accordance with one aspect of the invention, a method of assembling an integrated circuit is provided. An interposer supported by an integrated handler is solder bumped onto one or more bond pads on a substrate. The integrated handler is removed from the interposer. A side of the interposer opposite that of the substrate is solder bumped to one or more bond pads on a chip. 
         [0007]    In accordance with another aspect of the invention, a method of assembling an integrated circuit is provided. An interposer supported by an integrated handler is solder bumped to a temporary chip attach structure. The integrated handler is removed from the interposer. A side of the interposer opposite that of the temporary chip attach structure is solder bumped to one or more bond pads of a chip to form an interposer-chip stack on the temporary chip attach structure. The interposer-chip stack is removed from the temporary chip attach structure. The interposer-chip stack is solder bumped to one or more bonding pads on a substrate. 
         [0008]    Additional embodiments of the present invention may include the steps of cleaning the interposer after the handler is removed and reballing the solder bumps after the interposer-chip stack is removed from the temporary chip attach structure. 
         [0009]    In accordance with another aspect of the invention, an integrated circuit is provided. The integrated circuit comprises a die having one or more bond pads. One or more solder bumps are connected to the one or more bond pads of the die. An interposer is connected via the one or more solder bumps to the one or more bond pads of the die. 
         [0010]    Further embodiments of the present invention may comprise underfill between the die and interposer surrounding the one or more solder bumps. These embodiments may also comprise one or more additional solder bumps on a side of the interposer opposite that of the die, and a substrate having a one or more bond pads connected to the one or more additional solder bumps on a side of the interposer opposite that of the die. 
         [0011]    These and other objects, features, and advantages of the present invention will become apparent from the following detailed description of the illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a diagram illustrating a bumping and assembly process of a Si carrier to a ceramic substrate, according to an embodiment of the present invention; 
           [0013]      FIG. 2  is a diagram illustrating a bumping and assembly process of a Si carrier to a ceramic substrate using a TCA, according to an embodiment of the present invention; 
           [0014]      FIG. 3  is a diagram illustrating substrate first bumping and assembly process of a Si carrier, according to an embodiment of the present invention; 
           [0015]      FIG. 4  is a diagram illustrating a bumping and assembly process of a Si carrier to an organic substrate using a TCA, according to an embodiment of the present invention; 
           [0016]      FIG. 5  is a diagram illustrating a bumping and assembly process of an Si carrier that enables fine pitch capability for conventional TCA structures, according to an embodiment of the present invention; 
           [0017]      FIG. 6  is a flow diagram illustrating a bumping and assembly methodology for a Si carrier, according to an embodiment of the present invention; 
           [0018]      FIG. 7  is a flow diagram illustrating a bumping and assembly methodology for an Si carrier using a TCA, according to an embodiment of the present invention; and 
           [0019]      FIG. 8  is a block diagram illustrating an example of a bonding system in which a bumping and assembly technique of the invention may be implemented. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    As will be described in detail below, the present invention in the illustrative embodiment achieves assembly of Si carrier to chips and substrate to permit effective assembly, test and high yield. 
         [0021]    Referring initially to  FIG. 1 , a diagram illustrates a bumping and assembly process of a Si carrier for ceramic substrates, according to an embodiment of the present invention. An interposer  102  with an integrated handler  104  is provided. Interposer  102  is preferably a Si interposer. Interposer  102  has a high bandwidth but is very fragile and thin (20-100 microns) and thus requires a handler. Handler  104  may be a glass handler as shown in  FIG. 1 . Handler  104  allows for safe handling and assembly of thin Si interposer  102 . Solder bumps  106  are formed on an underside of Si interposer  102 , for attachment to bond pads of a module  108 , or Si carrier. Handler  104  holds thin Si interposer  102  flat to assist the solder bumps to contact bond pads on module  108 . Integrated handler  104  is removed through a laser, UV, thermal or vacuum release leaving Si interposer  102  to be supported by module  108 . For example, a porous glass handler may be dissolved through a chemical reaction. The surface of Si interposer is cleaned by ashing or reactive ion etch (RIE), before additional solder bumps  110  are formed on a top surface of Si interposer  102  for connection to an integrated circuit die or chip  112 . 97/3 PbSn or Pb-free SnCu solder bumps may be provided for both the chip and interposer. Additionally, 97/3 PbSn solder bumps may be provided for the chip, while 90/10 or 85/15 PbSn solder bumps may be provided for the interposer. Finally 97/3 PbSn solder bumps may be provided for the chip, while 63/37 PbSn solder bumps may be provided for the interposer. 
         [0022]    Referring now to  FIG. 2 , a diagram illustrates a bumping and assembly process of a Si carrier to a ceramic substrate using a temporary chip attach (TCA) structure, according to an embodiment of the present invention. A Si interposer  202  with an integrated handler  204  is provided. Solder bumps  206  are formed on an underside of Si interposer  202  for attachment to a TCA structure  208 . Handler  204  is removed through a laser, UV, thermal or mechanical process, leaving Si interposer  202  to be supported by TCA structure  208 . The surface of Si interposer  202  is cleaned by ashing or RWE, before additional solder bumps  210  are formed on a top surface of Si interposer  202  for connection to an integrated circuit die or chip  212 . TCA structure  208  is removed from stacked interposer-chip assembly  214 , and solder bumps  206  are re-balled for connection to bond pads of a module  216 . 97/3 PbSn or Pb-free SnCu solder bumps may be provided for both the chip and interposer. Additionally, 97/3 PbSn solder bumps may be provided for the chip, while 90/10 or 85/15 PbSn solder bumps may be provided for the interposer. Finally 97/3 PbSn solder bumps may be provided for the chip, while 63/37 PbSn solder bumps may be provided for the interposer. 
         [0023]    Referring now to  FIG. 3 , a diagram illustrates substrate first bumping and assembly process of a Si carrier, according to an embodiment of the present invention. A Si interposer  302  with handler  304  is provided. Solder bumps  306  are formed on an underside of Si interposer  302  for attachment to a substrate  308 . Handler  304  is removed through laser ablation, leaving Si interposer  302  to be supported by substrate  308 . The surface of Si interposer  302  is cleaned by ashing before additional solder bumps  310  are formed on a top surface of Si interposer  302  for connection to bond pads of an integrated circuit die or chip  312 . Si interposer  302  may also provide connections for multiple chips  312 . 97/3 PbSn solder bumps may be provided for the chip and 90/10 or 85/15 PbSn solder bumps may be provided for the interposer. 
         [0024]    Referring now to  FIG. 4 , a diagram illustrates a bumping and assembly process of a Si carrier to an organic substrate using a TCA structure, according to an embodiment of the present invention. A Si interposer  402  with handler  404  is provided. Solder bumps  406  are formed on an underside of Si interposer  402  for attachment to a TCA structure  408 . Handler  404  is removed through a laser, UV, thermal or mechanical process, leaving Si interposer  402  to be supported by TCA structure  408 . The surface of Si interposer  402  is cleaned by ashing before additional solder bumps  410  are formed on a top surface of Si interposer for connection to bond pads of an integrated circuit die or chip  412 . TCA structure  408  is removed from stacked interposer-chip assembly  414 , and solder bumps  406  are re-balled for connection to bond pads of a module  416 . 97/3 PbSn solder bumps may be provided for the chip and interposer and 63/37 PbSn solder bumps may be provided for the organic substrate. The solder bumps may be Pb-free SnCu solder bumps for the chip and interposer. Further, 97/3 PbSn solder bumps may be provided for the chip, 90/10 or 85/15 PbSn solder bumps may be provided for the interposer, and 63/37 PbSn solder bumps may be provided for the organic substrate. Finally, 97/3 PbSn solder bumps may be provided fro the chip and 63/37 PbSn solder bumps may be provided for the interposer and the substrate. 
         [0025]    Referring now to  FIG. 5 , a diagram illustrates a bumping and assembly process of a Si carrier that enables fine pitch capability for conventional TCA structures, according to an embodiment of the present invention. A Si interposer  502  having a handler  504  is connected via solder bumps  506  to a TCA structure  508 . Handler  504  is removed through a laser, UV, thermal or mechanical process, leaving Si interposer  502  to be supported by TCA structure  508 . The surface of Si interposer  502  is cleaned by ashing before additional solder bumps  510  are formed on a top surface of Si interposer for connection to bond pads of an integrated circuit die or chip  512 . Si interposer  502  and TCA structure  508  are removed from chip  512  and solder bumps  510  are re-balled for connection of chip  512  to a module  514 . 97/3 PbSn or Pb-free SnCu solder bumps may be provided for both the chip and interposer. Additionally, 97/3 PbSn solder bumps may be provided for the chip, while 90/10 or 85/15 PbSn solder bumps may be provided for the interposer. Finally 97/3 PbSn solder bumps may be provided for the chip, while 63/37 PbSn solder bumps may be provided for the interposer. 
         [0026]    Referring now to  FIG. 6 , a flow diagram illustrates a bumping and assembly methodology for a Si carrier, according to an embodiment of the present invention. The methodology begins in block  602  in which an interposer and integrated handler are solder bumped to bond pads of a substrate or module. In block  604 , the integrated handler is removed from the interposer. In block  606 , the surface of the interposer is cleaned. Finally, in block  608 , the top surface of the interposer is solder bumped to bond pads of a chip, terminating the methodology. 
         [0027]    Referring now to  FIG. 7 , a flow diagram illustrates a bumping and assembly methodology for a Si carrier using a TCA, according to an embodiment of the present invention. The methodology begins in block  702  in which an interposer and integrated handler are solder bumped to a TCA structure. In block  704 , the integrated handler is removed from the interposer. In block  706 , the top surface of the interposer is cleaned. In block  708 , the top surface of the interposer is solder bumped to bond pads of a chip. In block  710 , the interposer-chip stack is removed from the TCA structure. In block  712 , solder bumps that previously connected the interposer-chip stack to the TCA structure are re-balled. Finally, in block  714 , the interposer-chip stack is solder bumped to bond pads of a substrate or module. 
         [0028]    Referring now to  FIG. 8 , a block diagram illustrates an example of bonding system  800  in which a bumping and assembly technique of the invention may be implemented. As illustrated, the system  800  comprises a soldering tool  802  coupled to a computer  804  which may comprise a processor  806  and a memory  808 . One or more of the steps shown in  FIG. 1-7  may be performed at least in part utilizing software executed by processor  806  and stored in memory  808 . 
         [0029]    Additional embodiments of the present invention may incorporate various numbers and combinations of transistor dies, tuning capacitors, leads, or other circuit elements, arranged in various configurations within a given integrated circuit. 
         [0030]    Therefore, although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modification may be made by one skilled in the art without departing from the scope or spirit of the invention.