Abstract:
A microelectronic device structure including increased thermal dissipation capabilities. The structure including a three-dimensional (3D) integrated chip assembly that is flip chip bonded to a substrate. The chip assembly including a device substrate including an active device disposed thereon. A cap layer is physically bonded to the device substrate to at least partially define a hermetic seal about the active device. The microelectronic device structure provides a plurality of heat dissipation paths therethrough to dissipate heat generated therein.

Description:
BACKGROUND 
     Embodiments presented herein relate to microelectronic device structures and, more particularly, to three-dimensional (3D) microelectronic integrated circuit (IC) chip structures including increased thermal dissipation capability. 
     Microelectromechanical systems (MEMS) are miniaturized devices, such as microswitches that may range in size from less than 1 micron to about 1 mm or more. 3D integrated circuits in general, include two or more layers of electronic components in a stacked configuration that are integrated both vertically and horizontally. These devices generally require a controlled environment to operate for a long period of time. Dissipation of heat is a major issue in any high-power electronics or electrical application, and extremely important in high-powered microelectromechanical systems or MEMS devices. Through substrate vias, referred to as TSVs, are utilized as conductors in the stack of chips, such as memory chips, providing amongst other functions, a heat path between the chips. Additional means for dissipating heat may be integrated. 
     Most MEMS devices are interconnected using wirebonding. However, in high power MEMS applications, wirebonding can lead to severe limitations in the performance of the device. Limitations associated with wirebonding are related to the following factors, including, but not limited to, current handling capability of the wires and an insufficient thermal path that may particularly impact handling of short current surges. In other instances, MEMS device may be interconnected using ribbon bonding with similar limitations in the performance of the device. 
     In addition to performance degradation due to inadequate thermal dissipation, the introduction of contaminants such as moisture, particulates or gas into the environment surrounding the device can cause sticking, contamination, or interference of the metal contacts, leading to device failure. 
     Accordingly, an improved microelectronic chip structure including increased thermal management, such as improved heat dissipation paths, resulting in a more reliable high-performance device with increased current carrying capabilities may be desired. In addition, it may provide protection from contaminants to an active device. 
     BRIEF DESCRIPTION 
     Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below. 
     In accordance with certain embodiments, disclosed is an apparatus including a three-dimensional (3D) integrated chip assembly and a substrate, wherein the three-dimensional (3D) integrated chip assembly is flip chip bonded to a substrate, and wherein a plurality of heat dissipation paths extend through the three-dimensional (3D) integrated chip assembly to dissipate heat generated therein. The chip assembly including a device substrate; an active device comprising one or more heat generating elements disposed on the device substrate; a cap layer physically bonded to the device substrate; and a hermetic seal formed about the active device, the hermetic seal at least partially defined by the device substrate and the cap layer. 
     In accordance with other embodiments, disclosed is an apparatus including a three-dimensional (3D) integrated chip assembly, a substrate and a heat spreader positioned proximate the three-dimensional (3D) integrated chip assembly via a thermal interface material (TIM). The three-dimensional (3D) integrated chip assembly is flip chip bonded to the substrate. The apparatus provides a plurality of heat dissipation paths through the three-dimensional (3D) integrated chip assembly to dissipate heat generated within the apparatus. The chip assembly including a device substrate; an active device comprising one or more integrated circuits disposed on the device substrate; a cap layer comprising a semiconductor material, the cap layer physically bonded to the device substrate; a hermetic seal formed about the active device, the hermetic seal at least partially defined by the device substrate and the cap layer. 
     In accordance with further embodiments, disclosed is an apparatus including a MEMS device including a cap layer and a hermetic seal, at least partially defined by the cap layer, and a substrate. The MEMS device is configured to be flip chip bonded to the substrate. 
     In accordance with further embodiments, disclosed is a method of dissipating heat within an apparatus including providing a three-dimensional (3D) integrated chip assembly. The method of providing the chip assembly including providing a device substrate having a first main surface and a second main surface, disposing an active device comprising one or more integrated circuits on the device substrate, bonding a cap layer to the device substrate, forming a hermetic seal about the active device and providing a substrate including a plurality of input/output connections. The device substrate including a plurality of input/output connections on at least one of the first main surface and the second main surface. The cap layer having a first main surface and a second main surface and including a plurality of input/output connections on at least one of the first main surface and the second main surface. The hermetic seal at least partially defined by the device substrate and the cap layer. The method further provides flip chip bonding the three-dimensional (3D) integrated chip assembly to the substrate to form an apparatus, wherein the apparatus provides a plurality of heat dissipation paths through the three-dimensional (3D) integrated chip assembly to dissipate heat generated within the apparatus. 
     Various refinements of the features noted above exist in relation to the various aspects of the present invention. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present invention alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of the present invention without limitation to the claimed subject matter. 
    
    
     
       DRAWINGS 
       The terms “top” and “bottom” are not used here because parts of the assembly are processed partly in one orientation, and partly in another. Instead, the terms “first surface” and “second surface” are used, such that all of the first surfaces eventually face the same direction in the finished device structure and all second surfaces eventually face the same direction in the finished device structure. 
         FIG. 1  illustrates in cross-section, a device structure including a three-dimensional integrated electronic assembly having increased thermal dissipation capabilities according to an embodiment; 
         FIG. 2  illustrates in cross-section, the device structure of  FIG. 1  indicating heat dissipation paths according to an embodiment; 
         FIG. 3  illustrates in cross-section, a device structure including a three-dimensional integrated electronic assembly having increased thermal dissipation capabilities according to another embodiment; 
         FIG. 4  illustrates in cross-section, a device structure including a three-dimensional integrated electronic assembly having increased thermal dissipation capabilities according to yet another embodiment; and 
         FIG. 5  illustrates in graphical representation, a comparison of thermal dissipation at transient current rise conditions in a device structure according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliant with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     Disclosed is an innovative 3D integrated microelectronic chip assembly, and in particular a microelectromechanical systems (MEMS) device including a means for improved thermal management. The 3D integrated device assembly includes integrated layers and parallel connected interconnects to aid in efficient thermal dissipation of heat generated within the device structure and provide increased current carrying capabilities, while lowering electrical resistance in the interconnect structures. 
     The drawings show example structures for microelectronic devices, and in particular MEMS devices, including the 3D integrated chip assembly capable of improved thermal dissipation. Referring now to the drawings, in which like numerals refer to like elements throughout the several views, and in particular  FIG. 1 , illustrated is a cross-sectional embodiment of one example of a device structure employing a 3D integrated chip assembly with increased thermal dissipation capabilities. This device structure, generally denoted  100 , includes a 3D integrated chip assembly  105  mounted to a substrate  110  having a first main surface  111  and a second main surface  112 . The 3D integrated chip assembly  105  in general comprises a cap layer  114  having a first main surface  122  and a second main surface  124  and a device substrate  132  having a first main surface  140  and a second main surface  150 . During fabrication of the device structure  100 , the 3D integrated chip assembly  105  is mounted to the second main surface  112  of the substrate  110 . In this particular embodiment of the device structure  100 , the cap layer  114  is mounted via a first main surface  122  to the substrate  110  utilizing a plurality of micro-bump connections  115 , also referred to herein as flip chip bump bonding, that allow for high current carrying capabilities. The device substrate  132  is mounted onto a second main surface  124  of the cap layer  114 , via a first main surface  140  of the device substrate  132  via standard metal interconnects (described presently). A heat spreader  152  may be positioned on a second main surface  150  of the device substrate  132  via a thermal interface material (TIM)  154 . In combination, the stacked elements, including the substrate  110 , the cap layer  114 , the device substrate  132 , the interconnects between the multiple layers, the thermal interface material  154  and the heat spreader  152  form the device structure  100 . 
     In this particular embodiment, the substrate  110  for electrical interconnection may be a printed circuit board (PCB) well known in the art. However, those skilled in the art will recognize that the substrate material in an alternative embodiment may comprise an active device layer, such as a metal-oxide semiconductor (MOS) based layer, including, silicon, silicon carbide, gallium-arsenide, etc., or when not considered an active layer, may be comprised of any flat supportive material, such as a polished metal, a flexible plastic, polyimide, a semiconductor material, or an insulator such as glass or a quartz material. 
     In this particular embodiment, the device substrate  132  may be formed of silicon well known in the art. However, those skilled in the art will recognize that the device substrate material in an alternative embodiment may comprise any flat supportive material compatible with semiconductor and MEMS based fabrication and packaging processes, such as silicon, silicon carbide, gallium arsenide, gallium nitride, alumina, sapphire, titanium, steel, plastics, polyimide, glass, quartz etc. 
     The second main surface  112  of the substrate  110  contains a plurality of input/output contacts  116  which are shown soldered via a plurality of parallel configured solder bumps  118  to a plurality of first input/output contacts  120  disposed on the first main surface  122  of the cap layer  114  and configured to match the input/output contacts  116  of the substrate  110 . Standard wafer processes are used to fabricate the substrate  110  layer&#39;s plurality of input/output contacts  116 , patterned and located to match the input/output contacts of a cap layer  114  (described presently) to which the 3D integrated chip assembly  105 , and more particularly the cap layer  114 , is to be attached. The plurality of input/output contacts  116  could be constructed as one or more metal layers, e.g., copper, nickel and/or gold layers. The actual composition of the metal layers in the input/output contact stacks would be dependent on the substrate  110  materials. In an embodiment, the device substrate  132  and cap layer  114  are first bonded together to form the 3D integrated chip assembly  105 , also referred to herein as a “MEMS” or “device chip”, that is then attached via solder bumps  118  to the substrate  110 . In a preferred embodiment, many parallel bumps are used to serve as high current carriers as well as thermal shunts. The parallel microbump interconnections can range from 2 to 50 or even more in number per IO depending on the package size, IO count, etc. 
     An underfill material  121 , as is well known in the art, is illustrated as disposed between the substrate  110  and the cap layer  114 . The underfill material  121  can be used to fill in the space between the substrate  110  and the cap layer  114  so that the micro-bump connections  115 , and more particularly the plurality of input/output connections  116 , the plurality of first input/output connections  120  and the solder bumps  118  remain secured. In the event of different coefficients of expansion between the substrate  110  and the cap layer  114 , they may expand or contract by different amounts when the device structure  100  is heated or cooled due to the heat generated during operation. This heating or cooling of the device structure  100  may create relative motion between the various device structure  100  layers. The inclusion of the underfill material  121  may aid in preventing the interconnects between the substrate  110  and the cap layer  114  becoming unsecured. 
     The cap layer  114  is further configured to support on the second main surface  124 , a plurality of second input/output contacts  126  configured to match, or otherwise interface to or be compatible with, a plurality of input/output contacts (described presently) formed on the device substrate  132 . Interconnects from the lower main surface  122  of the cap layer  114  to the second main surface  124  can be achieved by various means, including constructing a plurality of through substrate vias  128 , and more particularly a plurality of through silicon vias (TSVs)  128 , constructed using, for example, laser, high rate reactive ion etching, etc., for via formation and standard wafer processes for via metallization. 
     As shown, the plurality of first input/output contacts  120  electrically connect via the plurality of through wafer vias  130  to the plurality of second input/output contacts  126  disposed on the second main surface  124  of the cap layer  114 . The plurality of through wafer vias  130  are electrically isolated from the cap layer  114 . 
     One embodiment of the device  100  described herein includes the fabrication of the cap layer  114  of a semiconductor material, and for example, matching the cap layer  114  material to the substrate  110  to which it is to be connected, when the substrate  110  is not a printed circuit board (PCB). More specifically, one method of fabricating the device structure  100  is to select the cap layer  114  of a semiconductor material to match the material employed by the substrate  110 ; for example, silicon. This minimizes mechanical stress, strain and otherwise provides a high reliability package and interconnects, and also provides for an electrical interconnect performance equivalent. By way of example, if the device structure  100  includes a silicon substrate  110  then the cap layer  114  may also be fabricated of silicon. Since silicon based integrated circuit devices predominate today, the discussion provided herein may discuss a silicon cap layer  114 . However, those skilled in the art will recognize that the device substrate material and the cap layer material could comprise any semiconductor material, including, silicon, silicon carbide, gallium-arsenide, etc. or alternatively a material such as quartz, or the like. Standard wafer processes can be employed to fabricate the cap layer  114 , including creating the plurality of first input/output contacts  120  on the cap layer  114  using wafer processing. 
     After the cap layer  114  material is selected, the plurality of through wafer  130  are created (by, for example, plasma etching, drilling, laser drilling, chemical etching, high rate reactive ion etching, laser ablation, etc., through the cap layer  114 ), optionally insulated to electrically isolate the cap layer  114  and subsequent electrical interconnections, and then metalized to form electrical connections from the first main surface  122  of the cap layer  114  to the second main surface  124  of the cap layer  114 . 
     Following via creation as previously described, standard wafer processes (photolithography, wet chemistry, physical vapor deposition (PVD), electroplating, etc.) can be employed to create the metalized through wafer vias  130 . One embodiment of the through-via construction process is to use wet chemistry (to relieve stress) followed by oxidation to establish an insulative layer partially covering the surface of the cap layer  114  and the walls of the vias (without filling the vias) to provide the necessary electrical isolation from the cap layer  114 . Seed metal is then deposited to establish a metal layer in the vias, prior to plating the vias with metal, for example, copper, nickel, gold, etc. A photomask is applied and the circuitry (e.g., input/output) contacts and interconnect to the through vias, if any, is patterned. Once complete, cap layer  114  such as depicted in  FIG. 1  is attained, wherein the metalized through vias extend from the first main surface  122  to the second main surface  124  of the cap layer  114 . 
     Following through-via creation, standard wafer processes are used to fabricate the cap layer&#39;s  114  plurality of input/output contacts  126 , patterned and located to match the input/output contacts of a device substrate  132  to which the cap layer  114  is to be attached, in addition to fabricating the plurality of first input/output contacts  120 . On the opposite first main surface  122  of the cap layer  114 , for example, the plurality of input/output contacts  120  are formed. The pluralities of input/output contacts  120  and  126  could be constructed as a stack of metal layers, e.g., copper, nickel and/or gold layers. The actual composition of the metal layers in the input/output contact stacks would be dependent on the cap layer  114  material and attachment method used. 
     In the embodiment of  FIG. 1 , the plurality of through wafer vias  130  formed within the cap layer  114  are aligned under or in close proximity to the plurality of first input/output contacts  120  to be disposed on the first main surface  122  of the cap layer  114  and the plurality of second input/output contacts  126  to be disposed on the second main surface  124  of the cap layer  114 . The plurality of second input/output contacts  126 , in one embodiment, are patterned to match a plurality of input/output contacts  138  or pad configuration of the device substrate  132  to which the cap layer  114  is to be attached, while the plurality of second input/output contacts  120  are configured to facilitate connection to the substrate  110  which the cap layer  114  is also to be connected. In one embodiment, the diameters of the through wafer vias  130  are dependent on the quantity of through wafer vias  130  and location of the device substrate  132 , plurality of input/output contacts  138  and plurality of input/output contacts  116 . For high density input/output configurations, the diameter of each via  130  may be as small as ten microns or less using today&#39;s technology. 
     As shown, the plurality of first input/output contacts  120  disposed on the first main surface  122  of the cap layer  114  electrically connect via metalized vias  130  to the plurality of second input/output contacts  126  disposed on the second main surface  124  of the cap layer  114 . 
     The device substrate  132 , as previously described, includes a plurality of input/output contacts  138  formed on the first main surface  140 . The plurality of input/output contacts  138  are shown bonded, such as through thermocompression bonding, to the plurality of second input/output contacts  126  disposed on the second main surface  124  of the cap layer  114  and configured to match the input/output contacts  126  of the cap layer  114 . It should be understood that although two separate layers are depicted throughout the figures to form the interconnections  125 , any number of layers of materials may be utilized. Thermally conductive traces  143  provide for interconnect of an active device to the first main surface  140  of the device substrate  132  and dissipation of heat (described presently). The term “active device” as used herein may comprise any heat generating element, such as a semiconducting integrated circuit (IC), a simple resistor, a sensor such as an acoustic (ultrasound) sensor, an optical (LCD, photodiode, spatial light modulator) device, or any similar type heat generating device. In the illustrated exemplary embodiment, the active device  144  comprises a microelectromechanical system (MEMS) circuit and in particular a micro scale relay. 
     As illustrated in  FIG. 1 , a sealing ring  146  provides hermetic sealing of the active device  144 . The sealing ring  146  may be comprised of any known sealing material, such as glass frit, eutectic metal compositions, polymer adhesives, thermal compressive metal bonds, or the like. In an embodiment including a glass frit sealing ring  146 , during assembly, a glass frit ring, such as a thixotropic paste, may be screen printed onto one of the device substrate  132  or the cap layer  114  and dried. In an example embodiment, the frit thickness is in the 5 to 20 micron range. The printed glass frit ring will eventually form a hermetic seal  148  for the individual active device(s)  144 . To form the hermetic seal  148 , a wafer bonding process, to melt the glass particles, is performed thereby creating the sealing ring  146  and the hermetic seal  148 . Typical wafer processing of the glass frit ring may employ glass reflow and bonding temperatures of approximately 400° C. under vacuum and with an applied wafer-to-wafer force. The reflowed glass frit sealing process will permit the sealing ring  146  to hermetically seal the active device  144  between the second main surface  124  of the cap layer  114  and the first main surface  140  of the device substrate  132 . Due to the movement generated by the mechanical components during operation, the active device  144  is susceptible to external air and unwanted particles, such as moisture, dust particles, or the like. The sealing ring  146  and hermetic seal  148  about the active device  144  may provide protection from these unwanted contaminants. 
     A second main surface  150  of the device substrate  132  may be attached to an optional heat spreader  152 , via a thermal interface material (TIM)  154  disposed therebetween. In the illustrated embodiment, heat generated by the active device  144  may be dissipated through the heat spreader  152  into the external environment. The inclusion of the heat spreader  152  and the TIM  154  may be dependent upon the need for additional heat dissipation capabilities within the structure  100 . 
     The cap layer  114 , hermetic sealing of the active device  144 , plurality of parallel interconnects and overall device structure  100  constructed as discussed above may alleviate some or all of the problems associated with heat dissipation in high powered microelectronic chip structures, and more particularly high powered microelectromechanical systems (MEMS). In addition, the 3D integrated chip assembly  105  constructed as described herein, can be easily picked and placed with a high-accuracy, high volume placement machine and assembled onto the substrate  110  for packaging. 
     Referring now to  FIG. 2 , illustrated is the device structure  100 , constructed according to the previous description, depicting a plurality of heat dissipation paths  156  according to an embodiment. As previously stated, like numerals refer to like elements throughout the several views. During transient current conditions, the plurality of heat dissipation paths  156 , as illustrated, are available. The heat dissipation paths  156  as disclosed herein place the heat generation in direct connection with dissipation over the power lines compared to heat spreaders which require heat to first flow through the bulk substrate, then through the TIM and then to the heat spreader. As illustrated, during operation, heat generated by the device structure  100 , and more particularly the active device  144 , is dissipated via the plurality of heat dissipation paths  156 , and in particular along thermally conductive traces  143  on the wafer or cap surface that take heat from the device  144  to the interconnect structure  125  and down the solder bump flip chip assembly  115 . The heat dissipation paths  156  provide a continuous thermally conductive metal pathway from the active device  144  to its metal interconnections, thus serving as the primary path for heat dissipation. The flip chip interconnects  115  provide many thermal dissipation paths  156  through each electrical joint that are better thermally coupled to the heat generation source, and more particularly the active device  144 , than solely relying on heat dissipation through bulk silicon, or the like. In addition to providing for many parallel shorter electrical paths  156 , the flip chip interconnects  115  provide for shorter dissipation paths  156 . As depicted, heat may be dissipated by the microbump interconnects  115  formed by the flip chip joints located between the substrate  110  and the cap layer  114 , and the metal interconnections  125  formed between the cap layer  114  and the device substrate  132 . Any additional heat may be dissipated through the heat spreader  152 , when included in the device structure  100 . The described novel flip chip approach provides for a shorter interconnect path length, thereby making it more favorable to dissipate heat. Such short and highly parallelized thermal paths serve a significant advantage over other interconnection methods such as wire-bonds and ribbon bonding. 
     Further examples of device structure configurations employing higher power heat dissipation capabilities are depicted in  FIGS. 3 and 4 , in which like numerals again refer to like elements throughout the several views. Referring more specifically to  FIG. 3 , illustrated is another embodiment of a device structure  200  including a substrate  110 , and a 3D integrated chip assembly  105  generally comprising a cap layer  114  and a device substrate  132 . In this particular embodiment, and in contrast to the embodiment depicted in  FIGS. 1 and 2 , the device substrate  132  is disposed in a lower portion of the 3D integrated chip assembly  105  and more particularly, the cap layer  114  is disposed on a first main surface  150  of the device substrate  132 . In addition, the active device  144  is positioned via thermally conductive traces  143  on the second main surface  150  of the device substrate  132 . The device substrate  132  further includes a plurality of through wafer vias  128  formed therein and a plurality of first input/output contacts  120  disposed over a first main surface  140  thereof, wherein the plurality of second input/output contacts  120  are electrically connected to the active device  144  through the plurality of through wafer vias  130 . Similarly configured flip chip bump interconnects to those of the first embodiment illustrated in  FIGS. 1 and 2  are formed between a second main surface  112  of the substrate  110  and the first main surface  140  of the device substrate  132 . An underfill material  121  may be provided. The sealing ring  146  forms a hermetic seal  148  for the active device  144  between the device substrate  132  and the cap layer  114 . In addition, the sealing ring  146  provides a physical bond between the second main surface  150  of the device substrate  132  and the first main surface  122  of the cap layer  114 . In this particular embodiment, and in contrast to the embodiment depicted in  FIGS. 1 and 2 , the heat spreader  152  and the thermal interface material  154  have been omitted. Similar to the first disclosed embodiment, heat generated by the device structure  200 , and more particularly the active device  144 , is dissipated in a similar manner according to heat dissipation paths illustrated in  FIG. 2 . It should additionally be understood that irrespective of the configuration of the cap layer  114  and the device substrate  132  within the 3D integrated chip assembly  105 , the inclusion of the thermal interface material  154  and the heat spreader  152  remain dependent upon the need for additional heat dissipation capabilities. 
     Referring now to  FIG. 4 , illustrated is yet another embodiment of a device structure  300  including a substrate  110  and a 3D integrated chip assembly  105  generally comprising a cap layer  114  and a device substrate  132 , configured in a stack generally similar to the embodiment described in  FIGS. 1 and 2 . In this particular embodiment, and in contrast to the embodiment depicted in  FIGS. 1 and 2 , the heat spreader  152  and the thermal interface material  154  have been omitted. An optional heat spreader  152  is positioned on the first main surface  124  of the cap layer  114  via a thermal interface material (TIM)  154 . In this particular embodiment, the sealing ring is omitted, and a hermetic seal  148  for the active device  144  is formed by the device substrate  132 , the cap layer  114 , and the metal interconnects  125  formed between the cap layer  114  and the device substrate  132 . More specifically, the plurality of second input/output contacts  126  formed on the second main surface  124  of the cap layer  114  and the plurality of input/output contacts  138  formed on the first main surface  140  of the device substrate  132 , provide for the hermetic seal  148  about the active device  144 . In yet, another alternate embodiment, an additional interconnect-via structure can be included about the active device  144 , comprising a set of metal interconnects  125  formed between the cap layer  114  and the device substrate  132 , vias  130 , and interconnects  116 ,  120  and bumps  118  formed between the cap layer  114  and the substrate  110  may be included to form an additional seal. 
     Similar to the previously disclosed embodiments, heat generated by the device structure  300 , and more particularly the active device  144 , is dissipated in a similar manner according to heat dissipation paths illustrated in  FIG. 2 . It should be understood that while  FIG. 4  includes the 3D integrated chip assembly  105  configured wherein the cap layer  114  is positioned to allow for attachment to the substrate  110 , in an alternative embodiment, the cap layer  114  and device substrate  132  may be reversed with respect to configuration in the 3D integrated chip assembly  105 , such as described and illustrated in  FIG. 3 , to allow for attachment of the device substrate  132  to the substrate  110 . It should additionally be understood that irrespective of the configuration of the cap layer  114  and the device substrate  132  within the 3D integrated chip assembly  105 , the inclusion of the thermal interface material  154  and the heat spreader  152  remain dependent upon the need for additional heat dissipation capabilities. 
     Illustrated in  FIG. 5 , are simulation results  400  depicting heat dissipation of embodiments of a high powered microelectronic device structure including known interconnect/stack configurations and the novel interconnect/stack configurations described herein. More specifically, heat dissipation is graphically represented in  FIG. 5  to illustrate the improved heat dissipation qualities of a flip chip board configuration. Current (A) is represented on an x-axis  402  the maximum temperature in the package (typically at the MEMS beams) and temperature (K) is represented on a y-axis  403 . Typical heat dissipation in a known microelectronic device structure, including standard wire bond/trace interconnects and a heat spreader is depicted at line  404 . As indicated, at a current of approximately 30 Amps, wire bond/trace interconnects limit the thermal conductivity of the packaged device causing the temperature to get excessively hot, and as illustrated in excess of 700 K. 
     Typical heat dissipation of a known microelectronic device structure including copper strap interconnects and a heat spreader is depicted at line  406 . As indicated, at a current of approximately 30 Amps the heat in a known device including copper strap interconnects, while capable of dissipating heat more efficiently than in the previous device including wire bond/trace interconnects, is only capable of dissipating heat wherein the device remains at a temperature in excess of 460 K. 
     Typical heat dissipation of a microelectronic device structures configured to include a cap layer, hermetic seal and interconnects as in the previously described embodiments of  FIG. 1-4  are depicted at lines  408  and  410 . As indicated at line  408 , at a current of approximately 30 Amps the heat in a novel device including a cap layer, hermetic seal, novel flip chip interconnects and a heat spreader, such as that described in  FIGS. 1-4  is capable of dissipating heat more efficiently than in previous known devices including wire bond/trace interconnects or ribbon-based interconnects. As depicted at line  408 , the temperature is efficiently dissipated and the temperature of the device at approximately 30 Amps is less than 400 K. 
     Typical heat dissipation of a microelectronic device structure configured to include a cap layer, hermetic seal and interconnects as in the previously described embodiment of  FIG. 4 , wherein a heat spreader is not incorporated in the device structure is depicted at line  410 . As indicated at line  410 , at a current of approximately 30 Amps the heat in a novel device including a cap layer and novel flip chip interconnects, but without the inclusion of a heat spreader, while dissipating less heat than the flip chip embodiment incorporating the heat spreader at line  408 , remains capable of dissipating heat more efficiently than in previous known devices including wire bond/trace interconnects or copper strap interconnects wherein a heat spreader was utilized. As depicted at line  410 , the temperature in this embodiment is efficiently dissipated and the temperature of the device at approximately 30 Amps is less than 450 K. 
     Those skilled in the art will understand from the above examples, that provided herein is a novel interconnect structure and device structure stack or package which can be employed to improve heat dissipation in high power microelectronic devices, such as microelectromechanical systems (MEMS) devices. By fabricating the device to include a 3D integrated chip assembly comprising a cap layer, a device substrate, a plurality of metal interconnects and an active device, a plurality of bump interconnects between the 3D integrated chip assembly and an underlying substrate and a hermetic seal about the active device and between the cap layer and the device substrate, a low cost, high performance, high yield device structure can be obtained using standard chemistry, mechanical processes, etc. Further, the device structure and techniques disclosed herein may result in advantages including, but not limited to, increased thermal management by way of increased heat dissipation capabilities, easier package integration and lower electrical resistance interconnects. Mechanical and thermal management systems for rather thin, fragile integrated circuit chips and devices are also provided. 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.