Abstract:
Multiple integrated circuit devices in a stacked configuration that use a spacing element for allowing increased device density and increased thermal conduction or heat removal for semiconductor devices and the methods for the stacking thereof are disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of application Ser. No. 10/933,843, filed Sep. 2, 2004, now U.S. Pat. No. 7,064,006, issued Jun. 20, 2006, which is a divisional of application Ser. No. 09/989,326, filed Nov. 20, 2001, now U.S. Pat. No. 6,911,723, issued Jun. 28, 2005, which is a continuation of application Ser. No. 09/247,009, filed Feb. 8, 1999, now U.S. Pat. No. 6,351,028, issued Feb. 26, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to the packaging of integrated circuit devices by interposing a plurality of integrated circuit devices within a common package for increased semiconductor device density. More particularly, the present invention relates to multiple integrated circuit devices in a stacked configuration that uses a spacing element allowing increased semiconductor device density and allowing better thermal conductivity for dissipating heat for semiconductor memory devices, semiconductor processor type devices, or any desired type integrated circuit semiconductor device. 
     2. State of the Art 
     Integrated circuit semiconductor devices have been known since shortly after the development of the electronic transistor device. The goals in designing and manufacturing semiconductor devices have been to make the devices smaller, more complex, with higher densities, and to include additional features. One method that improves the features and the densities of the semiconductor devices is to shrink the line sizes used in the lithographic process step in fabricating semiconductor devices. For example, each one-half reduction in line width of the circuits of the semiconductor device corresponds to a four-fold increase in chip density for the same size device. Unfortunately, increasing density simply through improved lithographic techniques is limited because of physical limits and the cost factor of scaling down the dimensions of the semiconductor device. Accordingly, alternative solutions to increase semiconductor device density have been pursued. One such alternative has been the stacking of multiple semiconductor devices. However, conventional stacking of semiconductor devices can lead to excessive local heating of the stacked semiconductor devices as well as lead to restraints on how the heat may be removed from the stacked semiconductor devices. 
     One approach of semiconductor device (die) stacking uses a chip geometry known as cubic chip design and is illustrated in drawing  FIG. 1  (Prior Art). The device  2  includes substrate  4 , upon which a plurality of semiconductor devices  6  is stacked. Each semiconductor device  6  is connected to another semiconductor device and to substrate  4  via bonding elements  8 , which are then encased in a suitable type of resin material  10  forming a package. The semiconductor devices  6  are designed such that an overhanging flange is provided by cutting the edges of a semiconductor device at approximately a 30- to 35-degree angle and inverting the device for the bonding connection. This allows the semiconductor devices  6  to stack one on top of another in a uniform and tight arrangement. 
     Unfortunately, the cubic design has several disadvantages that make it unsuitable for all types of semiconductor device packaging design. One disadvantage is that the cubic stacking of the semiconductor devices one on top of another causes stack stresses or bending, or both. Additionally, because of stack stressing or bending, there is a limit to the number of semiconductor devices that can be stacked one on top of another. Also, if the adhesive of the stack weakens and comes loose, the semiconductor device will shift, which can result in the breaking of the bonds between the various devices  6  and the substrate  4 . Furthermore, the stacking of the semiconductor devices generates thermal and mechanical problems where the semiconductor devices generate heat that cannot be easily dissipated when they are stacked one upon another. 
     Additional solutions have been developed in the prior art and are illustrated in U.S. Pat. Nos. 5,585,675 (&#39;675 patent) and 5,434,745 (&#39;745 patent). The &#39;675 patent discloses a packaging assembly for a plurality of semiconductor devices that provides for stacking of the semiconductor devices. The packaging assembly uses angularly offset pad-to-pad via structures that are configured to allow three-dimensional stacking of the semiconductor devices. The electrical connection is provided to a via structure where multiple identical tubes are provided in which a semiconductor device is mounted and then one tube is mounted on top of another tube. The angularly offset via pads are provided through the stack tube structure for connection. One disadvantage with the angularly offset pad via structure is that the tubes must be precisely manufactured so that the vias are lined up properly. Further, the semiconductor devices must be set within strict tolerances for the tubes to stack one on top of another so the vias can be aligned properly as well. 
     The &#39;745 patent discloses a stacked semiconductor device carrier assembly and a method for packaging interconnecting semiconductor devices. The carriers are constructed from a metal substrate onto which the semiconductor device attaches. Next, the semiconductor device is wired bonded to the conductor pattern on the substrate and each conductor is routed to the edge of the substrate where it is connected to a half circle of a metallized through-hole. Again, the &#39;745 patent discloses a tube-like design with half circle vias for allowing interconnection to the stack of multiple semiconductor devices. 
     One disadvantage with the stack type semiconductor device carrier of the &#39;745 patent is that the tubes are connected one with another. Any potential rework operation involving the wire connections is very difficult in that the tube assemblies must be disassembled for such a rework operation. 
     Accordingly, a multiple stacked arrangement of semiconductor devices and associated methods of stacking that reduce stack stresses or bending of the semiconductor devices, that allow easier reworking of the wiring interconnecting bond pads of the semiconductor devices, that protect the bond pads of each semiconductor device from the other devices, and that effectively remove heat from the semiconductor devices are needed. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to the packaging of integrated circuit devices by interposing a plurality of integrated circuit devices within a common package for increased semiconductor device density. The present invention relates to multiple integrated circuit devices in a stacked configuration that uses a spacing element for allowing increased device density and the removal of thermal energy from semiconductor devices and the methods for the stacking thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a prior art cubic semiconductor device package; 
         FIG. 2  is a cross-sectional diagram of an embodiment of the T-interposer devices of the present invention used for the stacking of multiple semiconductor devices according to the present invention; 
         FIG. 3  is a perspective view of an embodiment of a single T-interposer of the present invention; 
         FIG. 4  is a cross-sectional view of multiple semiconductor devices mounted to an embodiment of a T-interposer according to the present invention; 
         FIG. 5  is a cross-sectional diagram of another embodiment of T-interposers having differing dimensions of the present invention; 
         FIG. 6  is a perspective view of an embodiment of an inverted T-interposer of the present invention; 
         FIG. 7  is a cross-sectional view of a multiple semiconductor device (die) package that has a sealant about the interconnections; 
         FIG. 8  is a cross-sectional view of another embodiment of the T-interposer of the present invention in a stacked configuration; 
         FIG. 9  is a cross-sectional view of another embodiment of the T-interposer of the present invention in a stacked configuration; and 
         FIG. 10  is a block diagram of an electronic system incorporating the semiconductor device of  FIG. 2  and the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Illustrated in a cross-sectional diagram in drawing  FIG. 2  is a multi-stacked semiconductor device structure utilizing a T-interposer device having a T-shape in cross-section of the present invention. Multiple stack unit  20  comprises a substrate  22 ; a first semiconductor device  24  disposed on substrate  22 , a first T-interposer  26  disposed on the first semiconductor device  24 , and multiple semiconductor devices  24  disposed on multiple T-interposers  26 . Each semiconductor device  24  includes a plurality of bond pads  28  thereon. Each T-interposer  26  includes a substantially vertical stem  27  having substantially vertical edges and T-bar cross portions or members  29  having substantially horizontal edges or surfaces with respect to the vertical edges of the stem  27 , the upper surface  29 ′ of the T-bar members  29  extending across the stem  27  to form a substantially horizontal surface with respect to the vertical upon which to mount one or more semiconductor devices  24 . The flange (horizontal) edges or surfaces of each T-interposer  26  are offset so that a portion of the active surface  25  of each semiconductor device  24  attaches to the base of the stem  27  of an adjacent T-interposer  26  while bond pads  28  of each semiconductor device  24  are exposed for wire bonding to substrate  22  or another semiconductor device  24  or the circuit of another T-interposer  26 . Each semiconductor device  24  is subsequently stacked one on top of another in a horizontal plane with a T-interposer  26  disposed between each semiconductor device  24 . Each semiconductor device  24  may be bonded either to the T-interposer  26 , another semiconductor device  24 , or to substrate  22  or both. In this structure, the T-interposer  26  is placed on an individual semiconductor device  24  as other semiconductor devices  24  are stacked one on top of another, each stacked semiconductor device  24  being located in a separate substantially horizontal plane. This provides for access and protection to bond pads  28  of the semiconductor devices  24 . The T-interposer  26  can be made of a variety of materials, including those materials having a coefficient of thermal expansion (CTE) matching or similar to the semiconductor device(s)  24 , such as silicon, ceramic, alloy  42 , etc., and having the desired thermal energy (heat transfer or conductivity) characteristics for the transfer of thermal energy or beat from semiconductor devices in contact with or around T-interposer  26 . Alternately, the material for the T-interposer  26  may be selected for thermal energy insulation effects to prevent thermal energy from being transferred from one semiconductor device  24  connected to the T-interposer to another semiconductor device  24  connected to the T-interposer. 
     This protects the semiconductor devices  24  during the stacking and enables a variety of interconnections to be used between semiconductor devices  24 , T-interposers  26 , and/or substrates  22 . The interconnection between semiconductor devices  24  or T-interposers  26  or substrates  22 , or both, uses conductor traces, tape, wire bonding, conductive paste, or conductive adhesives, or any other type of suitable semiconductor interconnection technique known to one skilled in the art. The T-interposer  26  allows bond pads  28  of the semiconductor device  24  to be exposed, so no additional rerouting steps are required to reroute a bond pad  28  to the edges. This is advantageous over the prior art structures, such as the cubic design shown in drawing  FIG. 1 , in that the shell case or the interconnection requires additional processing in those materials and additional time. Further, the flanged edges forming the stem  27  of T-interposer  26  allow direct connection to the bond pads  28  and contact to all four sides of semiconductor devices  24 . This allows increased interconnect density between a substrate and a plurality of semiconductor devices. 
     In multiple stack unit  20 , if desired, the first semiconductor device  24 , which is mounted to substrate  22 , can be a microprocessor while the second semiconductor device  24 , located above T-interposer  26  mounted to the first semiconductor device  24  located on the substrate  22 , can be a semiconductor memory device, which allows for mixing and matching of the semiconductor devices such as memory devices and processing devices and control logic devices for a complete, integrated semiconductor device package. 
     Referring to drawing  FIG. 3 , further illustrated is an inverted T-interposer  26  as shown in drawing  FIG. 2 . Again, T-interposer  26  can be manufactured to match the same CTE of the semiconductor device  24  or the semiconductor device substrate  22  used for each of semiconductor devices  24 , or both. This allows T-interposer  26  to serve as a thermal or heat dissipation device between each semiconductor device  24  while allowing for greater heat dissipation than would otherwise be possible were the semiconductor devices  24  stacked directly upon each other. Further, T-interposer  26  provides electrical insulation between each semiconductor device  24  that would not be otherwise possible were the semiconductor devices to be stacked one upon another such as in the prior art described in drawing  FIG. 1 . Additionally, the T-interposer  26  may be comprised of two different materials to provide both thermal conductivity from one semiconductor device and thermal insulation with respect to a second semiconductor device. For instance, the stem  27  may be of a thermally conductive material while the T-bar members  29  are formed of a thermally insulative material; the stem  27  may be joined to the T-bar member(s)  29  by any suitable means, such as adhesive bonding, etc. The T-interposer  26  of the present invention provides for much greater bonding edge relief for different types of connection devices with respect to the bond pad  28  location on the active surface  25  of the semiconductor device  24  than that shown in the prior art device illustrated in drawing  FIG. 1  and greater insulation capacity for the bond pads  28  of the semiconductor devices  24  with the T-interposer  26  in place. Finally, a top T-interposer  26  is further provided for capping the device to protect and promote heat transfer from the last semiconductor device  24  forming the multiple stacked unit  20 . 
     Still referring to the T-interposer  26  illustrated in drawing  FIG. 3 , an electrical bonding interconnect element  30  is manufactured into T-interposer  26  to provide subsequent connection should the bond pads  28  on active surface  25  of the semiconductor device  24  be mounted or connected to the T-shaped interposer  26  for electrical interconnection. 
     Referring to drawing  FIG. 4 , illustrated is a cross-section diagram of multiple semiconductor devices  38  and  40  being mounted to a single T-interposer  26 . T-interposer  26  is mounted to a substrate  36 . Substrate  36  includes bond pads/circuits  28  thereon. Semiconductor device  38  can be a processor type semiconductor device while semiconductor device  40  can be a memory type semiconductor device. Semiconductor device  38  and semiconductor device  40  are interconnected via bond pads  28  and further connected to bond pads or circuits  28  on substrate  36 . Additionally, the bonding wire from one bond pad or circuit  28 , such as on device  40 , can connect directly to the device structure to which the substrate  36  is to be permanently mounted. This can be the actual circuit board, such as a mother board used in a computer system. Of course, other direct connection options will be readily apparent to one skilled in the art. 
     Referring to drawing  FIG. 5 , illustrated is a cross-sectional diagram of an arrangement of multiple semiconductor devices  24  similar to that illustrated in drawing  FIG. 4 . The present invention illustrated in drawing  FIG. 5  further adds multiple stacking upon a particular semiconductor device  24 . Multiple T-interposers  26  are provided and are of similar sizes. Additionally, semiconductor device  24  can be directly connected to T-interposer  26  below bond pad  28  thereon. In this manner, substrate  36  mounts directly to mother board substrate  22  where additional bonding pads  28  are provided in substrates  22  and  36 . 
     Referring to drawing  FIG. 6 , depicted is an alternative embodiment T-interposer  126  of the present invention, which is similar to the embodiment of the T-interposer  26  illustrated in drawing  FIG. 3 . As illustrated in drawing  FIG. 6 , the T-interposer  126  includes additional recessed sections all around. The entire recessed periphery allows semiconductor devices that have connection pads around the entire perimeter of the device to be exposed for connection. In this manner, greater inter-connectivity is achieved with the ability to connect very dense interconnected circuit devices to other semiconductor devices. Additionally, ball weld spots  128  are provided as well and allow direct electrical and mechanical connection of any subsequent semiconductor devices. The stem  127  of the T-interposer  126  includes T-members  129  therearound and substantially horizontal surface  129 ′ located thereabove as described hereinbefore with respect to T-interposer  26 . 
     Referring to drawing  FIG. 7 , illustrated is a cross-sectional view of a multiple stack unit  20  that is completely sealed or packaged. Again, a substrate  22  is provided upon which a first semiconductor device  24  is mounted with a T-interposer  26  mounted to the first semiconductor device  24 . A final cap or top T-interposer  26  is further provided on top of the entire stack unit  20 . Lastly, an epoxy interconnect  50  is provided for sealing and/or packaging and electrically isolating the bonding performed between the multiple semiconductor devices  24 . If desired, the top of the unit  20  may include a heat sink  52  of suitable type material which may include one or more fins  54  (shown in dashed lines) for additional thermal control of the heat from the unit  20 . 
     Referring to drawing  FIG. 8 , illustrated is another embodiment of the T-interposer  26  of the present invention in a stacked arrangement between semiconductor devices  40 , which are electrically connected by wires  56  to circuits  58  of the substrate  36 . In this embodiment of the T-interposer  26  of the present invention, one T-bar member  29  has a greater length or extends farther than the opposing T-bar member  29  of the T-interposer  26  to provide greater bonding edge relief for different types of connection devices with respect to the bond pad location on the active surface of the semiconductor device  24  than the bonding edge relief provided by the T-bar member  29  on the other side of the T-interposer  26 . In this manner, the T-interposer  26  is not centrally located on a portion of the active surface of the semiconductor device  40  but, rather, is located off-center on a portion of the active surface of the semiconductor device  40 . Such a T-interposer  26  allows for the accommodation of differing sizes and shapes of semiconductor devices  40  and bond pad arrangements thereon for interconnection to the circuits  58  of substrate  36 . 
     Referring to drawing  FIG. 9 , illustrated is another embodiment of the T-interposer  26  of the present invention where the T-interposer  26  includes a plurality of stems  27  and T-bar members  29  to form the same, each stem  27  located on a portion of the active surface of a semiconductor device  40 , which is, in turn, located on a substrate  36  having circuits  58  located thereon connected by wires  56  while wires  62  electrically connect the semiconductor devices  40  located on surface  29 ′ of the T-interposer  26  to the circuits  60  located thereon. In this manner, the T-interposer  26  helps to increase the density of the semiconductor devices  40  located on the substrate  36  while providing thermal control of the heat generated from the semiconductor devices  40  located on the substrate  36  and on the surface  29 ′ of the T-interposer  26 . 
     Each T-interposer  26  can be manufactured in various manners; ideally, the T-interposer  26  consists of a unitary element that is milled or machined from a single piece. The side edges for producing the “T” effect are milled away to preserve the integral strength of the unitary piece. This design prevents fractures occurring in seams of the T-interposer where the top “T” portion is epoxied to the bottom as a separate element. If desired, T-interposer  26  can be made from separate pieces, one having a smaller width than the other, if the epoxy or adhesive used to connect the two elements is of sufficient strength to prevent fracturing or separation, or the strain and load placed on the seams were greatly reduced so as to minimize the possibility of fracturing. 
     The use of the T-interposer  26  for stacking bare dies has several advantages over prior art solutions. One advantage is that it reduces stack stresses or bending. Further, the T-interposer allows easier reworking of any bond interconnect when necessary. Additionally, as there are no stress problems inherent in stacking semiconductor devices upon other devices, as any number of devices can be stacked with T-interposer  26  used in separating device from device, thus allowing for greater device densities for memory devices and other type semiconductor devices. Also, several types of interconnect methods are possible with the T-interposer, such as wire bonding, ball bonding, flip-chip bonding, etc. Additional advantages include the bond pads of each semiconductor device being protected from one another in the device stack. Thermal and mechanical properties are improved because of the use of the T-interposer. The improved thermal and mechanical properties also allow for increased semiconductor device density for memory chips and SIMM type devices. 
     Those skilled in the art will appreciate that semiconductor devices according to the present invention may comprise an integrated circuit die employed for storing or processing digital information, including, for example, a Dynamic Random Access Memory (DRAM) integrated circuit die, a Static Random Access Memory (SRAM) integrated circuit die, a Synchronous Graphics Random Access Memory (SGRAM) integrated circuit die, a Programmable Read-Only Memory (PROM) integrated circuit die, an Electrically Erasable PROM (EEPROM) integrated circuit die, a flash memory die and a microprocessor die, and that the present invention includes such devices within its scope. In addition, it will be understood that the shape, size, and configuration of bond pads, jumper pads, dice, and lead frames may be varied without departing from the scope of the invention and appended claims. For example, the jumper pads may be round, oblong, hemispherical or variously shaped and sized so long as the jumper pads provide enough surface area to accept attachment of one or more wire bonds thereto. In addition, the bond pads may be positioned at any location on the active surface of the die. 
     As shown in drawing  FIG. 10 , an electronic system  130  includes an input device  132  and an output device  134  coupled to a processor device  136 , which in turn, is coupled to a memory device  138  incorporating the exemplary semiconductor device  24  and T-interposer  26  of drawing  FIG. 2 . 
     Accordingly, the claims appended hereto are written to encompass all semiconductor devices including those mentioned. Those skilled in the art will also appreciate that various combinations and obvious modifications of the preferred embodiments may be made without departing from the spirit of this invention and the scope of the accompanying claims.