Abstract:
A thermally enhanced semiconductor assembly with three dimensional integration includes a stacked semiconductor sub-assembly electrically coupled to a wiring board by bonding wires. A heat spreader that provides an enhanced thermal characteristic for the stacked semiconductor sub-assembly is disposed in a through opening of a wiring structure. Another wiring structure disposed on the heat spreader not only provides mechanical support, but also allows heat spreading and electrical grounding for the heat spreader by metallized vias. The bonding wires provide electrical connections between the sub-assembly and the wiring board for interconnecting devices assembled in the sub-assembly to terminal pads provided in the wiring board.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. application Ser. No. 15/166,185 filed May 26, 2016, a continuation-in-part of U.S. application Ser. No. 15/289,126 filed Oct. 8, 2016, a continuation-in-part of U.S. application Ser. No. 15/353,537 filed Nov. 16, 2016, a continuation-in-part of U.S. application Ser. No. 15/415,844 filed Jan. 25, 2017, a continuation-in-part of U.S. application Ser. No. 15/415,846 filed Jan. 25, 2017 and a continuation-in-part of U.S. application Ser. No. 15/462,536 filed Mar. 17, 2017. The U.S. application Ser. No. 15/166,185 claims the priority benefit of U.S. Provisional Application Ser. No. 62/166,771 filed May 27, 2015. The U.S. application Ser. No. 15/289,126 is a continuation-in-part of U.S. application Ser. No. 15/166,185 filed May 26, 2016. The U.S. application Ser. No. 15/353,537 is a continuation-in-part of U.S. application Ser. No. 15/166,185 filed May 26, 2016 and a continuation-in-part of U.S. application Ser. No. 15/289,126 filed Oct. 8, 2016. The U.S. application Ser. Nos. 15/415,844, 15/415,846 and 15/462,536 are continuation-in-part of U.S. application Ser. No. 15/166,185 filed May 26, 2016, continuation-in-part of U.S. application Ser. No. 15/289,126 filed Oct. 8, 2016 and continuation-in-part of U.S. application Ser. No. 15/353,537 filed Nov. 16, 2016. The entirety of each of said applications is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a semiconductor assembly and, more particularly, to a thermally enhanced semiconductor assembly with three dimensional integration in which a stacked semiconductor sub-assembly is wire bonded to and thermally conductible to a wiring board having a heat spreader integrated with dual wiring structures, and a method of making the same. 
       DESCRIPTION OF RELATED ART 
       [0003]    Market trends of multimedia devices demand for faster and slimmer designs. One of assembly approaches is to interconnect two devices with stacking configuration so that the routing distance between the two devices can be the shortest possible. As the stacked devices can talk directly to each other with reduced latency, the assembly&#39;s signal integrity and additional power saving capability are greatly improved. However, as semiconductor devices are susceptible to performance degradation at high operational temperatures, stacking chips without proper heat dissipation would worsen devices&#39; thermal environment and may cause immediate failure during operation. 
         [0004]    Additionally, U.S. Pat. Nos. 8,008,121, 8,519,537 and 8,558,395 disclose various assembly structures having an interposer disposed in between the face-to-face chips. Although there is no TSV in the stacked chips, the TSV in the interposer that serves for circuitry routing between chips induces complicated manufacturing processes, high yield loss and excessive cost. 
         [0005]    For the reasons stated above, and for other reasons stated below, an urgent need exists to provide a three dimensional semiconductor assembly that can address high packaging density, better signal integrity and high thermal dissipation requirements. 
       SUMMARY OF THE INVENTION 
       [0006]    The objective of the present invention is to provide a thermally enhanced semiconductor assembly in which a stacked semiconductor sub-assembly is electrically connected to a wiring board through a plurality of bonding wires and thermal conductible to a heat spreader provided in the wiring board. The heat spreader is disposed in a through opening of a wiring structure and mechanically supported by, electrically connected with, and thermally dissipated through another wiring structure, thereby improving mechanical, thermal and electrical performances of the assembly. 
         [0007]    In accordance with the foregoing and other objectives, the present invention provides a thermally enhanced semiconductor assembly having a stacked semiconductor sub-assembly electrically connected to a wiring board through bonding wires. The stacked semiconductor sub-assembly includes a first device, a second device and a routing circuitry. The wiring board includes a heat spreader, a first wiring structure and a second wiring structure. In a preferred embodiment, the first device is thermally conductible to the heat spreader and spaced from and electrically connected to the second device through the routing circuitry; the routing circuitry provides primary fan-out routing and the shortest interconnection distance between the first device and the second device; the first wiring structure laterally surrounds peripheral edges of the heat spreader and the sub-assembly, and is electrically coupled to the routing circuitry by bonding wires to provide further fan-out routing; and the second wiring structure covers the first wiring structure and the heat spreader to provide mechanically support, and is thermally conductible to the heat spreader and electrically coupled to the first wiring structure. 
         [0008]    Accordingly, the present invention provides a thermally enhanced semiconductor assembly with three dimensional integration, comprising: a stacked semiconductor sub-assembly that includes a first device, a second device and a routing circuitry, wherein the first device is electrically coupled to a first surface of the routing circuitry and the second device is electrically coupled to a second surface of the routing circuitry opposite to the first surface; a wiring board that includes a first wiring structure, a second wiring structure and a heat spreader, wherein (i) the first wiring structure has a first surface, an opposite second surface, and a through opening extending from the first surface and to the second surface, (ii) the heat spreader is disposed in the through opening and has a backside surface substantially coplanar with the first surface of the first wiring structure, (iii) the second wiring structure is disposed on the backside surface of the heat spreader and the first surface of the first wiring structure and electrically connected to the first wiring structure and thermally conductible to the heat spreader through metallized vias, and (iv) the stacked semiconductor sub-assembly is disposed in the through opening; and a plurality of bonding wires that electrically couple the routing circuitry to the wiring board. 
         [0009]    Additionally, the present invention provides a method of making a thermally enhanced semiconductor assembly with three dimensional integration, comprising: providing a stacked semiconductor sub-assembly that includes a first device, a second device and a routing circuitry, wherein the first device is electrically coupled to a first surface of the routing circuitry and the second device is electrically coupled to a second surface of the routing circuitry opposite to the first surface; providing a wiring board that includes a first wiring structure, a second wiring structure and a heat spreader, wherein (i) the first wiring structure has a first surface, an opposite second surface, and a through opening extending from the first surface to the second surface, (ii) the heat spreader is disposed in the through opening and has a backside surface substantially coplanar with the first surface of the first wiring structure, and (iii) the second wiring structure is disposed on the backside surface of the heat spreader and the first surface of the first wiring structure and electrically connected to the first wiring structure and thermally conductible to the heat spreader through metallized vias; disposing the stacked semiconductor sub-assembly in the through opening of the first wiring structure and over the heat spreader; and providing a plurality of bonding wires that electrically couple the routing circuitry and the wiring board. 
         [0010]    Unless specifically indicated or using the term “then” between steps, or steps necessarily occurring in a certain order, the sequence of the above-mentioned steps is not limited to that set forth above and may be changed or reordered according to desired design. 
         [0011]    The semiconductor assembly and the method of making the same according to the present invention have numerous advantages. For instance, stacking and electrically coupling the first and second devices to both opposite sides of the routing circuitry can offer the shortest interconnect distance between the first and second devices. Inserting the sub-assembly into the through opening of the first wiring structure of the wiring board is particularly advantageous as the wiring board can provide mechanical housing for the sub-assembly, whereas the heat spreader in the through opening and mechanically supported by the second wiring structure can provide thermal dissipation for the first device. Additionally, attaching the bonding wires to the sub-assembly and the wiring board can offer a reliable connecting channel for interconnecting the devices assembled in the sub-assembly to terminal pads provided in the wiring board. 
         [0012]    These and other features and advantages of the present invention will be further described and more readily apparent from the detailed description of the preferred embodiments which follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The following detailed description of the preferred embodiments of the present invention can best be understood when read in conjunction with the following drawings, in which: 
           [0014]      FIG. 1  is a cross-sectional view of a structure with routing traces formed on a sacrificial carrier in accordance with the first embodiment of the present invention; 
           [0015]      FIG. 2  is a cross-sectional view of the structure of  FIG. 1  further provided with a dielectric layer and via openings in accordance with the first embodiment of the present invention; 
           [0016]      FIG. 3  is a cross-sectional view of the structure of  FIG. 2  further provided with conductive traces in accordance with the first embodiment of the present invention; 
           [0017]      FIG. 4  is a cross-sectional view of the structure of  FIG. 3  further provided with a first device in accordance with the first embodiment of the present invention; 
           [0018]      FIG. 5  is a cross-sectional view of the structure of  FIG. 4  further provided with a molding compound in accordance with the first embodiment of the present invention; 
           [0019]      FIG. 6  is a cross-sectional view of the structure of  FIG. 5  after removal of the sacrificial carrier in accordance with the first embodiment of the present invention; 
           [0020]      FIG. 7  is a cross-sectional view of the structure of  FIG. 6  further provided with a second device to finish the fabrication of a stacked semiconductor sub-assembly in accordance with the first embodiment of the present invention; 
           [0021]      FIG. 8  is a cross-sectional view of a first wiring structure in accordance with the first embodiment of the present invention; 
           [0022]      FIG. 9  is a cross-sectional view of the structure of  FIG. 8  further provided with a heat spreader in accordance with the first embodiment of the present invention; 
           [0023]      FIG. 10  is a cross-sectional view of the structure of  FIG. 9  further provided with a second wiring structure to finish the fabrication of a wiring board in accordance with the first embodiment of the present invention; 
           [0024]      FIG. 11  is a cross-sectional view of the structure of  FIG. 10  further provided with the stacked semiconductor sub-assembly of  FIG. 7  in accordance with the first embodiment of the present invention; 
           [0025]      FIG. 12  is a cross-sectional view of the structure of  FIG. 11  further provided with bonding wires to finish the fabrication of a semiconductor assembly in accordance with the first embodiment of the present invention; 
           [0026]      FIG. 13  is a cross-sectional view of the structure of  FIG. 12  further provided with an encapsulant in accordance with the first embodiment of the present invention; 
           [0027]      FIG. 14  is a cross-sectional view of the structure of  FIG. 13  further provided with a third device in accordance with the first embodiment of the present invention; 
           [0028]      FIG. 15  is a cross-sectional view of the structure of  FIG. 14  further provided with solder balls in accordance with the first embodiment of the present invention; 
           [0029]      FIG. 16  is a cross-sectional view of the structure of  FIG. 13  further provided with passive components, an additional heat spreader and solder balls in accordance with the first embodiment of the present invention; 
           [0030]      FIG. 17  is a cross-sectional view of the inverted structure of FIG.  13  further provided with third devices, an additional heat spreader and solder balls in accordance with the first embodiment of the present invention; 
           [0031]      FIG. 18  is a cross-sectional view of the structure of  FIG. 13  further provided with an additional wiring board in accordance with the first embodiment of the present invention; 
           [0032]      FIG. 19  is a cross-sectional view of the structure of  FIG. 18  further provided with third devices and solder balls in accordance with the first embodiment of the present invention; 
           [0033]      FIG. 20  is a cross-sectional view of the structure of  FIG. 13  further provided with another aspect of the additional wiring board in accordance with the first embodiment of the present invention; 
           [0034]      FIG. 21  is a cross-sectional view of a wiring board in accordance with the second embodiment of the present invention; 
           [0035]      FIG. 22  is a cross-sectional view of the structure of  FIG. 21  further provided with the stacked semiconductor sub-assembly of  FIG. 7  in accordance with the second embodiment of the present invention; 
           [0036]      FIG. 23  is a cross-sectional view of the structure of  FIG. 22  further provided with bonding wires to finish the fabrication of a semiconductor assembly in accordance with the second embodiment of the present invention; 
           [0037]      FIG. 24  is a cross-sectional view of the structure of  FIG. 23  further provided with an encapsulant in accordance with the second embodiment of the present invention; 
           [0038]      FIG. 25  is a cross-sectional view of the inverted structure of  FIG. 24  further provided with a third device and passive components in accordance with the second embodiment of the present invention; 
           [0039]      FIG. 26  is a cross-sectional view of the inverted structure of  FIG. 25  further provided with an encapsulant in accordance with the second embodiment of the present invention; 
           [0040]      FIG. 27  is a cross-sectional view of the inverted structure of  FIG. 26  further provided with solder balls in accordance with the second embodiment of the present invention; 
           [0041]      FIG. 28  is a cross-sectional view of the structure with a stacked semiconductor sub-assembly attached to the wiring board of  FIG. 10  in accordance with the third embodiment of the present invention; 
           [0042]      FIG. 29  is a cross-sectional view of the structure of  FIG. 28  further provided with bonding wires in accordance with the third embodiment of the present invention; 
           [0043]      FIG. 30  is a cross-sectional view of the structure of  FIG. 29  further provided with vertical connecting elements in accordance with the third embodiment of the present invention; 
           [0044]      FIG. 31  is a cross-sectional view of the structure of  FIG. 30  further provided with an encapsulant to finish the fabrication of a semiconductor assembly in accordance with the third embodiment of the present invention; 
           [0045]      FIG. 32  is a cross-sectional view of the structure of  FIG. 31  further provided with a third device in accordance with the third embodiment of the present invention; 
           [0046]      FIG. 33  is a cross-sectional view of the structure of  FIG. 32  further provided with solder balls in accordance with the third embodiment of the present invention; 
           [0047]      FIG. 34  is a cross-sectional view of another aspect of the semiconductor assembly in accordance with the third embodiment of the present invention; 
           [0048]      FIG. 35  is a cross-sectional view of yet another aspect of the semiconductor assembly in accordance with the third embodiment of the present invention; 
           [0049]      FIG. 36  is a cross-sectional view of a stacked semiconductor sub-assembly in accordance with the fourth embodiment of the present invention; 
           [0050]      FIG. 37  is a cross-sectional view of the structure with the sub-assembly of  FIG. 36  wire bonded to the wiring board  30  of  FIG. 10  in accordance with the fourth embodiment of the present invention; 
           [0051]      FIG. 38  is a cross-sectional view of the structure of  FIG. 37  further provided with an encapsulant in accordance with the fourth embodiment of the present invention; 
           [0052]      FIG. 39  is a cross-sectional view of the structure of  FIG. 38  further provided with a third device in accordance with the fourth embodiment of the present invention; 
           [0053]      FIG. 40  is a cross-sectional view of the inverted structure of  FIG. 38  further provided with third devices, a heat spreader and solder balls in accordance with the fourth embodiment of the present invention; 
           [0054]      FIG. 41  is a cross-sectional view of a semiconductor assembly in accordance with the fifth embodiment of the present invention; 
           [0055]      FIG. 42  is a cross-sectional view of the structure of  FIG. 41  further provided with a third device and solder balls in accordance with the fifth embodiment of the present invention; 
           [0056]      FIG. 43  is a cross-sectional view of the structure of  FIG. 41  further provided with a lens and solder balls in accordance with the fifth embodiment of the present invention; 
           [0057]      FIG. 44  is a cross-sectional view of a semiconductor assembly in accordance with the sixth embodiment of the present invention; 
           [0058]      FIG. 45  is a cross-sectional view of the structure of  FIG. 44  further provided with a third device and solder balls in accordance with the fifth embodiment of the present invention; and 
           [0059]      FIG. 46  is a cross-sectional view of the structure of  FIG. 44  further provided with a lens and solder balls in accordance with the sixth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0060]    Hereafter, examples will be provided to illustrate the embodiments of the present invention. Advantages and effects of the invention will become more apparent from the following description of the present invention. It should be noted that these accompanying figures are simplified and illustrative. The quantity, shape and size of components shown in the figures may be modified according to practical conditions, and the arrangement of components may be more complex. Other various aspects also may be practiced or applied in the invention, and various modifications and variations can be made without departing from the spirit of the invention based on various concepts and applications. 
       Embodiment 1 
       [0061]      FIGS. 1-12  are schematic views showing a method of making a semiconductor assembly that includes a routing circuitry  21 , a first device  22 , a molding compound  25 , a second device  27 , a wiring board  30  and bonding wires  41  in accordance with the first embodiment of the present invention. 
         [0062]      FIG. 1  is a cross-sectional view of the structure with routing traces  212  formed on a sacrificial carrier  10 . The sacrificial carrier  10  typically is made of copper, aluminum, iron, nickel, tin, stainless steel, silicon, or other metals or alloys, but any other conductive or non-conductive material also may be used. In this embodiment, the sacrificial carrier  10  is made of an iron-based material. The routing traces  212  typically are made of copper and can be pattern deposited by numerous techniques, such as electroplating, electroless plating, evaporating, sputtering or their combinations, or be thin-film deposited followed by a metal patterning process. For a conductive sacrificial carrier  10 , the routing traces  212  are deposited typically by plating of metal. The metal patterning techniques include wet etching, electro-chemical etching, laser-assist etching, and their combinations with an etch mask (not shown) thereon that defines the routing traces  212 . 
         [0063]      FIG. 2  is a cross-sectional view of the structure with a dielectric layer  215  on the sacrificial carrier  10  as well as the routing traces  212  and via openings  216  in the dielectric layer  215 . The dielectric layer  215  is deposited typically by lamination or coating, and contacts and covers and extends laterally on the sacrificial carrier  10  and the routing traces  212  from above. The dielectric layer  215  typically has a thickness of 50 microns, and can be made of epoxy resin, glass-epoxy, polyimide, or the like. After the deposition of the dielectric layer  215 , the via openings  216  are formed by numerous techniques, such as laser drilling, plasma etching and photolithography, and typically have a diameter of 50 microns. Laser drilling can be enhanced by a pulsed laser. Alternatively, a scanning laser beam with a metal mask can be used. The via openings  216  extend through the dielectric layer  215  and are aligned with selected portions of the routing traces  212 . 
         [0064]    Referring now to  FIG. 3 , conductive traces  217  are formed on the dielectric layer  215  by metal deposition and metal patterning process. The conductive traces  217  extend from the routing traces  212  in the upward direction, fill up the via openings  216  to form metallized vias  218  in direct contact with the routing traces  212 , and extend laterally on the dielectric layer  215 . As a result, the conductive traces  217  can provide horizontal signal routing in both the X and Y directions and vertical routing through the via openings  216  and serve as electrical connections for the routing traces  212 . 
         [0065]    The conductive traces  217  can be deposited as a single layer or multiple layers by any of numerous techniques, such as electroplating, electroless plating, evaporating, sputtering, or their combinations. For instance, they can be deposited by first dipping the structure in an activator solution to render the dielectric layer  215  catalytic to electroless copper, and then a thin copper layer is electroles sly plated to serve as the seeding layer before a second copper layer is electroplated on the seeding layer to a desirable thickness. Alternatively, the seeding layer can be formed by sputtering a thin film such as titanium/copper before depositing the electroplated copper layer on the seeding layer. Once the desired thickness is achieved, the plated layer can be patterned to form the conductive traces  217  by any of numerous techniques such as wet etching, electro-chemical etching, laser-assist etching, or their combinations, with an etch mask (not shown) thereon that defines the conductive traces  217 . 
         [0066]    At this stage, the formation of a routing circuitry  21  on the sacrificial carrier  10  is accomplished. In this illustration, the routing circuitry  21  is a multi-layered buildup circuitry and includes routing traces  212 , a dielectric layer  215  and conductive traces  217 . 
         [0067]      FIG. 4  is a cross-sectional view of the structure with a first device  22  electrically coupled to the routing circuitry  21 . The first device  22  can be electrically coupled to the conductive traces  217  of the routing circuitry  21  using first bumps  223  in contact with the first device  22  and the first routing circuitry  21  by thermal compression, solder reflow or thermosonic bonding. In this example, the first device  22  is illustrated as a semiconductor chip. 
         [0068]      FIG. 5  is a cross-sectional view of the structure with a molding compound  25  on the routing circuitry  21  and around the first device  22  by, for example, resin-glass lamination, resin-glass coating or molding. The molding compound  25  covers the routing circuitry  21  from above and surrounds and conformally coats and covers sidewalls of the first device  22 . As an alternative, the step of providing the molding compound  25  may be omitted. 
         [0069]      FIG. 6  is a cross-sectional view of the structure after removal of the sacrificial carrier  10 . The sacrificial carrier  10  can be removed to expose the routing circuitry  21  from below by numerous techniques, such as wet chemical etching using acidic solution (e.g., ferric chloride, copper sulfate solutions), or alkaline solution (e.g., ammonia solution), electro-chemical etching, or mechanical process such as a drill or end mill followed by chemical etching. In this embodiment, the sacrificial carrier  10  made of an iron-based material is removed by a chemical etching solution that is selective between copper and iron so as to prevent the copper routing traces  212  from being etched during removal of the sacrificial carrier  10 . 
         [0070]      FIG. 7  is a cross-sectional view of the structure with a second device  27  electrically coupled to the routing circuitry  21 . The second device  27  can be electrically coupled to the routing traces  212  of the routing circuitry  21  using second bumps  273  in contact with the second device  27  and the routing circuitry  21  by thermal compression, solder reflow or thermosonic bonding. In this example, the second device  27  is illustrated as a semiconductor chip. However, in some cases, the second device  27  may be a packaged device or a passive component. 
         [0071]    At this stage, a stacked semiconductor sub-assembly  20  is accomplished and includes a routing circuitry  21 , a first device  22 , a molding compound  25 , and a second device  27 . The first device  22  and the second device  27  are electrically coupled to first and second surfaces  201 ,  202  of the routing circuitry  21 , respectively, and the molding compound  25  is disposed over the first surface  201  and laterally surrounds the first device  22 . 
         [0072]      FIG. 8  is a cross-sectional view of a first wiring structure  31 . The first wiring structure  31  has a through opening  315  extending from its first surface  311  to its second surface  312 . In this illustration, the first wiring structure  31  includes an interconnect substrate  32 , a first buildup circuitry  33  and a second buildup circuitry  34 . The interconnect substrate  32  includes a core layer  321 , a first routing layer  323 , a second routing layer  324  and metallized through vias  327 . The first routing layer  323  and the second routing layer  324  respectively extend laterally on both sides of the core layer  321 , and metallized through vias  327  extend through the core layer  321  to provide electrical connections between the first routing layer  323  and the second routing layer  324 . The first buildup circuitry  33  and the second buildup circuitry  34  are respectively disposed on both sides of the interconnect substrate  32 , and each of them includes a dielectric layer  331 ,  341  and conductive traces  333 ,  343 . The dielectric layers  331 ,  341  respectively cover both sides of the interconnect substrate  32  from below and above, and can be made of epoxy resin, glass-epoxy, polyimide, or the like. The conductive traces  333 ,  343  respectively extend laterally on the dielectric layers  331 ,  341 , and include metallized vias  334 ,  344  in the dielectric layers  331 ,  341 . The metallized vias  334 ,  344  contact the first and second routing layers  323 ,  324  of the interconnect substrate  32 , and extend through the dielectric layers  331 ,  341 . 
         [0073]      FIG. 9  is a cross-sectional view of the structure with a heat spreader  35  disposed in the through opening  315  of the first wiring structure  31 . The heat spreader  35  can be a thermally conductive layer made of, for example, metal, alloy, silicon, ceramic or graphite. In this embodiment, the heat spreader  35  is a metal layer and has a backside surface  351  substantially coplanar with the first surface  311  of the first wiring structure  31  from below. 
         [0074]      FIG. 10  is a cross-sectional view of the structure with a second wiring structure  36  formed on the backside surface  351  and the first surface  311  of the first wiring structure  31 . In this illustration, the second wiring structure  36  is a multi-layered buildup circuitry without a core layer, and includes multiple dielectric layers  361  and conductive traces  363  in an alternate fashion. The conductive traces  363  extend laterally on the dielectric layers  361  and include metallized vias  364  in the dielectric layers  361 . Accordingly, the second wiring structure  36  can be electrically coupled to the first wiring structure  31  and the heat spreader  35  through the metallized vias  364  embedded in the dielectric layers  361  and in contact with the first routing layer  323  and the heat spreader  35 . 
         [0075]    At this stage, a wiring board  30  is accomplished and includes a first wiring structure  31 , a heat spreader  35  and a second wiring structure  36 . As the depth of the through opening  315  is more than the thickness of the heat spreader  35 , the exterior surface of the heat spreader  35  and the sidewall surface of the through opening  315  of the first wiring structure  31  forms a cavity  316  in the through opening  315  of the first wiring structure  31 . As a result, the heat spreader  35  can provide thermal dissipation for a device accommodated in the cavity  316 , whereas the combination of the first wiring structure  31  and the second wiring structure  36  offers electrical contacts for next connection from two opposite sides of the wiring board  30 . 
         [0076]      FIG. 11  is a cross-sectional view of the structure with the stacked semiconductor sub-assembly  20  of  FIG. 7  attached to the wiring board  30  of  FIG. 10 . The stacked semiconductor sub-assembly  20  is aligned with and disposed in the through opening  315  of the first wiring structure  31 , with the first device  22  attached to the heat spreader  35  of the wiring board  30  using a thermally conductive material  39 . The thermally conductive material  39  can be a solder (e.g., AuSn) or a silver/epoxy adhesive. The interior sidewalls of the through opening  315  laterally surround and are spaced from peripheral edges of the stacked semiconductor sub-assembly  20 . As a result, a gap  317  is left in the through opening  315  between the peripheral edges of the stacked semiconductor sub-assembly  20  and the interior sidewalls of the first wiring structure  31 . The gap  317  laterally surrounds the stacked semiconductor sub-assembly  20  and is laterally surrounded by the first wiring structure  31 . 
         [0077]      FIG. 12  is a cross-sectional view of the structure with bonding wires  41  attached to the stacked semiconductor sub-assembly  20  and the wiring board  30  typically by gold or copper ball bonding, or gold or aluminum wedge bonding. The bonding wires  41  contact and are electrically coupled to the routing traces  212  of the routing circuitry  21  and the conductive traces  343  of the first wiring structure  31 . As a result, the bonding wires  41  can electrically couple the routing circuitry  21  to the first wiring structure  31 . 
         [0078]    Accordingly, as shown in  FIG. 12 , a semiconductor assembly  110  is accomplished and includes a stacked semiconductor sub-assembly  20  electrically connected to a wiring board  30  by bonding wires  41 . In this illustration, the stacked semiconductor sub-assembly  20  includes a routing circuitry  21 , a first device  22 , a molding compound  25  and a second device  27 , whereas the wiring board  30  includes a first wiring structure  31 , a heat spreader  35  and a second wiring structure  36 . 
         [0079]    The first device  22  is flip-chip electrically coupled to the routing circuitry  21  from one side of the routing circuitry  21  and enclosed by the molding compound  25  and the heat spreader  35 . The second device  27  is flip-chip electrically coupled to the routing circuitry  21  from the other side of the routing circuitry  21  and face-to-face connected to the first device  22  through the routing circuitry  21 . As such, the routing circuitry  21  offers primary fan-out routing and the shortest interconnection distance between the first device  22  and the second device  27 . The heat spreader  35  of the wiring board  30  is thermally conductible to and covers the first device  22  from below. The first wiring structure  31  laterally surrounds peripheral edges of the stacked semiconductor sub-assembly  20  and the heat spreader  35 , and is electrically coupled to the routing circuitry  21  by the bonding wires  41 . The second wiring structure  36  covers the first wiring structure  31  and the heat spreader  35  from below, and is electrically coupled to the first wiring structure  31  and thermally conductible to the heat spreader  35  through metallized vias  364 . As a result, the routing circuitry  21 , the first wiring structure  31  and the second wiring structure  36  can provide staged fan-out routing for the first device  22  and the second device  27 . 
         [0080]      FIG. 13  is a cross-sectional view of the semiconductor assembly  110  of  FIG. 12  further provided with an encapsulant  51 . The encapsulant  51  covers the bonding wires  41  and the stacked semiconductor sub-assembly  20  as well as selected portions of the wiring board  30  from above, and further fills up the gap  317  between the peripheral edges of the stacked semiconductor sub-assembly  20  and the interior sidewalls of the wiring board  30 . 
         [0081]      FIG. 14  is a cross-sectional view of the semiconductor assembly  110  of  FIG. 13  further provided with a third device  61  stacked over the stacked semiconductor sub-assembly  20  and the first wiring structure  31  of the wiring board  30 . The third device  61  can be a ball grid array package or a bumped chip, and is electrically coupled to the conductive traces  343  of the first wiring structure  31  through solder balls  71 . 
         [0082]      FIG. 15  is a cross-sectional view of the semiconductor assembly  110  of  FIG. 14  further provided with solder balls  73 . The solder balls  73  are mounted on the second wiring structure  36  of the wiring board  30  for external connection. 
         [0083]      FIG. 16  is a cross-sectional view of the semiconductor assembly  110  of  FIG. 13  further provided with passive components  65  and a heat spreader  81  at the first wiring structure  31  and solder balls  73  at the second wiring structure  36 . The passive components  65  are electrically coupled to the conductive traces  343  of the first wiring structure  31 . The heat spreader  81  has a cavity  811  and is mounted on the first wiring structure  31  and electrically coupled to the conductive traces  343  of the first wiring structure  31  for ground connection by solder balls  75 . The second device  27  is accommodated in the cavity  811  of the heat spreader  81  and thermally conductible to the heat spreader  81  by a thermally conductive material  89  in contact with the second device  27  and the heat spreader  81 . The solder balls  73  are mounted on the conductive traces  363  of the second wiring structure  36  for external connection. 
         [0084]      FIG. 17  is a cross-sectional view of the inverted semiconductor assembly  110  of  FIG. 13  further provided with third devices  61  and a heat spreader  81  at the second wiring structure  36  and solder balls  73  at the first wiring structure  31 . The third devices  61  can be ball grid array packages or bumped chips accommodated in a cavity  811  of the heat spreader  81 , and are electrically coupled to the conductive traces  363  of the second wiring structure  36  by solder balls  71 . The heat spreader  81  is thermally conductive to the third devices  61  using a thermally conductive material  89 , and electrically coupled to the conductive traces  363  of the second wiring structure  36  by solder balls  75 . The solder balls  73  are mounted on the conductive traces  343  of the first wiring structure  31  for external connection. 
         [0085]      FIG. 18  is a cross-sectional view of the semiconductor assembly  110  of  FIG. 13  further provided with an additional wiring board  90 . The wiring board  90  is stacked over the stacked semiconductor sub-assembly  20  and the wiring board  30 , and includes a third wiring structure  91 , a heat spreader  95  and a fourth wiring structure  96 . In this illustration, both the third wiring structure  91  and the fourth wiring structure  96  are multi-layered buildup circuitries without a core layer, and each includes multiple dielectric layers  911 ,  961  and conductive traces  913 ,  963  in an alternate fashion to provide electrical contacts at two opposite sides of the wiring board  90 . The third wiring structure  91  has a through opening  915  extending from its first surface  911  to its second surface  912 , and is electrically coupled to the conductive traces  343  of the first wiring structure  31  by solder balls  71 . The heat spreader  95  is disposed in the through opening  915  of the third wiring structure  91 , and has a backside surface  952  substantially coplanar with the second surface  912  of the third wiring structure  91 . The second device  27  is attached to and thermally conductible to the heat spreader  95  by a thermally conductive material  99  and laterally surrounded by the third wiring structure  91 . The fourth wiring structure  96  is disposed on the second surface  912  of the third wiring structure  91  and the backside surface  952  of the heat spreader  95 , and includes metallized vias  964  embedded in the dielectric layer  961  and in contact with the conductive traces  913  of the third wiring structure  91  and the heat spreader  95 . 
         [0086]      FIG. 19  is a cross-sectional view of the semiconductor assembly  110  of  FIG. 18  further provided with third devices  61  at the fourth wiring structure  96  and solder balls  73  at the second wiring structure  36 . The third devices  61  can be ball grid array packages or a bumped chips, and are stacked over and electrically coupled to the conductive traces  963  of the fourth wiring structure  96  through solder balls  77 . The solder balls  73  are mounted on the conductive traces  363  of the second wiring structure  36  for external connection. 
         [0087]      FIG. 20  is a cross-sectional view of the semiconductor assembly  110  of  FIG. 13  further provided with another aspect of the additional wiring board  90 . The wiring board  90  is similar to that illustrated in  FIG. 18 , except that the third wiring structure  91  is an interconnect substrate that includes a core layer  921 , a first routing layer  923 , a second routing layer  924 , and metallized through vias  927 . The first routing layer  923  and the second routing layer  924  are disposed on opposite sides of the core layer  921 . The metallized through vias  927  extend through the core layer  921  and are electrically coupled to the first routing layer  923  and the second routing layer  924 . The fourth wiring structure  96  includes metallized vias  964  in contact with the second routing layer  924  of the third wiring structure  91  and the heat spreader  95 . 
       Embodiment 2 
       [0088]      FIGS. 21-24  are schematic views showing a method of making a semiconductor assembly with the stacked semiconductor sub-assembly laterally surrounded by metallized sidewalls of the cavity of the wiring board in accordance with the second embodiment of the present invention. 
         [0089]    For purposes of brevity, any description in Embodiment 1 above is incorporated herein insofar as the same is applicable, and the same description need not be repeated. 
         [0090]      FIG. 21  is a cross-sectional view of a wiring board  30 . The wiring board  30  is similar to that illustrated in  FIG. 10 , except that (i) it further includes a metal layer  37  that completely covers sidewalls of the through opening  315  of the first wiring structure  31  and contacts the heat spreader  35 , and (ii) the outmost conductive traces  363  of the second wiring structure  36  includes a thermal pad  366 . In this illustration, the exterior surface of the heat spreader  35  and the lateral surface of the metal layer  37  forms a cavity  316  in the through opening  315  of the first wiring structure  31 . 
         [0091]      FIG. 22  is a cross-sectional view of the structure with the stacked semiconductor sub-assembly  20  of  FIG. 7  attached to the wiring board  30  of  FIG. 21 . The stacked semiconductor sub-assembly  20  is disposed in the cavity  316  of the wiring board  30  and attached to the heat spreader  35  using a thermally conductive material  39 . 
         [0092]      FIG. 23  is a cross-sectional view of the structure with bonding wires  41  attached to the stacked semiconductor sub-assembly  20  and the wiring board  30 . The bonding wires  41  contact and are electrically coupled to the routing traces  212  of the routing circuitry  21  and the conductive traces  343  of the first wiring structure  31 . 
         [0093]    Accordingly, as shown in  FIG. 23 , a semiconductor assembly  210  is accomplished and includes a stacked semiconductor sub-assembly  20  electrically connected to a wiring board  30  by bonding wires  41 . In this illustration, the stacked semiconductor sub-assembly  20  includes a routing circuitry  21 , a first device  22 , a molding compound  25  and a second device  27 , whereas the wiring board  30  includes a first wiring structure  31 , a heat spreader  35 , a second wiring structure  36  and a metal layer  37 . 
         [0094]    The first device  22  and the second device  27  are disposed at two opposite sides of the routing circuitry  21  and face-to-face electrically connected to each other through the routing circuitry  21  therebetween. As such, the routing circuitry  21  offers the shortest interconnection distance between the first device  22  and the second device  27 , and provides first level fan-out routing for the first device  22  and the second device  27 . The heat spreader  35  covers the inactive surface of the first device  22  and is thermally conductible to the first device  22 , whereas the metal layer  37  surrounds peripheral edges of the stacked semiconductor sub-assembly  20  and contacts the heat spreader  35 . The first wiring structure  31  is electrically coupled to the routing circuitry  21  through bonding wires  41 . The second wiring structure  36  covers the first wiring structure  31  and the heat spreader  35  from below, and is electrically coupled to the first wiring structure  31  for signal routing and to the heat spreader  35  for ground connection through metallized vias  364 . Accordingly, the combination of the first wiring structure  31  and the second wiring structure  36  can provide second level fan-out routing for the routing circuitry  21  and electrical contacts for next-level connection, whereas the combination of the heat spreader  35  and the metal layer  37 , electrically connected to the second wiring structure  36 , provides thermal dissipation and EMI shielding for the first device  22 . 
         [0095]      FIG. 24  is a cross-sectional view of the semiconductor assembly  210  of  FIG. 23  further provided with an encapsulant  51 . The encapsulant covers the bonding wires  41 , the stacked semiconductor sub-assembly  20  as well as selected portions of the first wiring structure  31  from above, and further fills up a gap  317  between the peripheral edges of the stacked semiconductor sub-assembly  20  and the interior sidewalls of the wiring board  30 . 
         [0096]      FIG. 25  is a cross-sectional view of the inverted semiconductor assembly  210  of  FIG. 24  further provided with a third device  61  and passive components  65 . The third device  61  is illustrated as a semiconductor chip, and is attached on the thermal pad  366  of the second wiring structure  36  and electrically coupled to the conductive traces  363  of the second wiring structure  36  by bonding wires  72 . The passive components  65  are mounted on and electrically coupled to the conductive traces  363  of the second wiring structure  36 . 
         [0097]      FIG. 26  is a cross-sectional view of the semiconductor assembly  210  of  FIG. 25  further provided with an encapsulant  85 . The encapsulant  85  covers the bonding wires  72 , the third device  61 , the passive components  65  and the second wiring structure  36  from above. 
         [0098]      FIG. 27  is a cross-sectional view of the semiconductor assembly  210  of  FIG. 26  further provided with solder balls  73 . The solder balls  73  are mounted on the conductive traces  343  of the first wiring structure  31  for external connection. 
       Embodiment 3 
       [0099]      FIGS. 28-31  are schematic views showing a method of making a semiconductor assembly with vertical connecting elements on the wiring board in accordance with the third embodiment of the present invention. 
         [0100]    For purposes of brevity, any description in Embodiments above is incorporated herein insofar as the same is applicable, and the same description need not be repeated. 
         [0101]      FIG. 28  is a cross-sectional view of the structure with a stacked semiconductor sub-assembly  20  disposed in the cavity  316  of the wiring board  30  of  FIG. 10 . The stacked semiconductor sub-assembly  20  is similar to that illustrated in  FIG. 7 , except that it further includes a passive component  23  and a metal pillar  24  electrically coupled to the routing circuitry  21  and encapsulated in the molding compound  25 . The stacked semiconductor sub-assembly  20  is attached on the heat spreader  35  by a thermally and electrically conductive material  38  in contact with the heat spreader  35 , the first device  22 , the metal pillar  24  and the molding compound  25 . 
         [0102]      FIG. 29  is a cross-sectional view of the structure with bonding wires  41  attached to the stacked semiconductor sub-assembly  20  and the wiring board  30 . The bonding wires  41  contact and are electrically coupled to the routing traces  212  of the routing circuitry  21  and the conductive traces  343  of the first wiring structure  31 . 
         [0103]      FIG. 30  is a cross-sectional view of the structure with vertical connecting elements  58  on the wiring board  30 . The vertical connecting elements  58  are electrically connected to and contact the conductive traces  343  of the first wiring structure  31 . In this examples, the vertical connecting elements  58  are illustrated as solder balls  581 . 
         [0104]      FIG. 31  is a cross-sectional view of the structure provided with an encapsulant  51 . The encapsulant  51  covers sidewalls of the vertical connecting elements  58  and the bonding wires  41 , the stacked semiconductor sub-assembly  20  and the wiring board  30  from above. Accordingly, a semiconductor assembly  310  is accomplished and includes a stacked semiconductor sub-assembly  20 , a wiring board  30 , bonding wires  41 , an encapsulant  51  and vertical connecting elements  58 . In this illustration, the stacked semiconductor sub-assembly  20  includes a routing circuitry  21 , a first device  22 , a passive component  23 , a metal pillar  24 , a molding compound  25  and a second device  27 , whereas the wiring board  30  includes a first wiring structure  31 , a heat spreader  35  and a second wiring structure  36 . 
         [0105]    The first device  22 /passive component  23  and the second device  27  are disposed at two opposite sides of the routing circuitry  21  and face-to-face electrically connected to each other through the routing circuitry  21  therebetween. The metal pillar  24  is electrically connected to the routing circuitry  21  and extends through the molding compound  25 . The heat spreader  35  is electrically connected to the metal pillar  24  for ground connection and thermally conductible to the first device  22  for heat dissipation. The combination of the first wiring structure  31  and the second wiring structure  36  is electrically coupled to the routing circuitry  21  using the bonding wires  41 , and electrically coupled to the heat spreader  35  through metallized vias  364 . The vertical connecting elements  58  are mounted on and electrically coupled to the first wiring structure  31  and laterally surrounded by the encapsulant  51 . 
         [0106]      FIG. 32  is a cross-sectional view of the semiconductor assembly  310  of  FIG. 31  further provided with a third device  61 . The third device  61  is stacked over the encapsulant  51 , and electrically coupled to the vertical connecting elements  58  in the encapsulant  51  through solder balls  71 . 
         [0107]      FIG. 33  is a cross-sectional view of the semiconductor assembly  310  of  FIG. 32  further provided with solder balls  73 . The solder balls  73  are mounted on the conductive traces  363  of the second wiring structure  36  for external connection. 
         [0108]      FIG. 34  is a cross-sectional view of another aspect of the semiconductor assembly according to the third embodiment of the present invention. The semiconductor assembly  320  is similar to that illustrated in  FIG. 31 , except that the encapsulant  51  has a larger thickness than that of the solder balls  581 , and has openings  511  to expose the solder balls  581  from above. 
         [0109]      FIG. 35  is a cross-sectional view of yet another aspect of the semiconductor assembly according to the third embodiment of the present invention. The semiconductor assembly  330  is similar to that illustrated in  FIG. 31 , except that it includes metal posts  583  as the vertical connecting elements  58 . 
       Embodiment 4 
       [0110]      FIGS. 36-37  are schematic views showing a method of making a semiconductor assembly with the second device wire bonded to the routing circuitry in accordance with the fourth embodiment of the present invention. 
         [0111]    For purposes of brevity, any description in Embodiments above is incorporated herein insofar as the same is applicable, and the same description need not be repeated. 
         [0112]      FIG. 36  is a cross-sectional view of a stacked semiconductor sub-assembly  20 . The stacked semiconductor sub-assembly  20  is similar to that illustrated in  FIG. 7 , except that the second device  27  is electrically coupled to the routing traces  212  of the routing circuitry  21  using bonding wires  276 . 
         [0113]      FIG. 37  is a cross-sectional view of a semiconductor assembly  410  with the stacked semiconductor sub-assembly  20  of  FIG. 36  electrically coupled to the wiring board  30  of  FIG. 10  through bonding wires  41 . The stacked semiconductor sub-assembly  20  is disposed in the cavity  316  of the wiring board  30  and attached to the heat spreader  35  using a thermally conductive material  39 . The bonding wires  41  contact and are electrically coupled to the routing traces  212  of the routing circuitry  21  and the conductive traces  343  of the first wiring structure  31 . 
         [0114]      FIG. 38  is a cross-sectional view of the semiconductor assembly  410  of  FIG. 37  further provided with an encapsulant  51 . The encapsulant  51  covers the bonding wires  41  and the stacked semiconductor sub-assembly  20  as well as selected portions of the wiring board  30  from above, and further fills up a gap  317  between the peripheral edges of the stacked semiconductor sub-assembly  20  and the interior sidewalls of the wiring board  30 . 
         [0115]      FIG. 39  is a cross-sectional view of the semiconductor assembly  410  of  FIG. 38  further provided with a third device  61  stacked over the stacked semiconductor sub-assembly  20  and the first wiring structure  31  of the wiring board  30 . The third device  61  is electrically coupled to the conductive traces  343  of the first wiring structure  31  through solder balls  71 . 
         [0116]      FIG. 40  is a cross-sectional view of the inverted semiconductor assembly  410  of  FIG. 38  further provided with third devices  61  and a heat spreader  81  at the second wiring structure  36  and solder balls  73  at the first wiring structure  31 . The third devices  61  are accommodated in a cavity  811  of the heat spreader  81 , and electrically coupled to the conductive traces  363  of the second wiring structure  36  by solder balls  71 . The heat spreader  81  is thermally conductive to the third devices  61  using a thermally conductive material  89 , and electrically coupled to the conductive traces  363  of the second wiring structure  36  by solder balls  75 . The solder balls  73  are mounted on the conductive traces  343  of the first wiring structure  31  for external connection. 
       Embodiment 5 
       [0117]      FIG. 41  is a cross-sectional view of a semiconductor assembly in accordance with the fifth embodiment of the present invention. 
         [0118]    The semiconductor assembly  510  is similar to that illustrated in  FIG. 12 , except that (i) the stacked semiconductor sub-assembly  20  further includes a passive component  23  electrically coupled to the routing circuitry  21  and encapsulated in the molding compound  25 , and (ii) the first wiring structure  31  of the wiring board  30  has a larger thickness to create a deeper cavity  316 , and the routing circuitry  21  and the second device  27  of the stacked semiconductor sub-assembly  20  also extend into the cavity  316  of the wiring board  30 . 
         [0119]      FIG. 42  is a cross-sectional view of the semiconductor assembly  510  of  FIG. 41  further provided with a third device  61  at the first wiring structure  31  and solder balls  73  at the second wiring structure  36 . The third device  61  is stacked over the stacked semiconductor sub-assembly  20  and the wiring board  30  and electrically coupled to the first wiring structure  31  through solder balls  71 . The solder balls  73  are mounted on and electrically coupled to the second wiring structure  36  for external connection. 
         [0120]      FIG. 43  is a cross-sectional view of the semiconductor assembly  510  of  FIG. 41  further provided with a lens  88  at the first wiring structure  31  and solder balls  73  at the second wiring structure  36 . The lens  88  optically transparent to at least one range of light wavelengths is stacked over the stacked semiconductor sub-assembly  20  and mounted to the first wiring structure  31  using a joining material  881 . The solder balls  73  are mounted on and electrically coupled to the second wiring structure  36  for external connection. The exemplary material of the lens  88  includes, but is not limited to, polycrystalline ceramics (e.g. aluminum oxide ceramics, aluminum oxynitride, perovskytes, polycrystalline yttrium aluminum garnet, etc.), single crystalline ceramics, non-crystalline materials (e.g. inorganic glasses and polymers), and glass ceramics (e.g. silicate based). The joining material  881  may be metal-based material (such as solder), epoxy-based material, polyimide, any other resin or appropriate material. 
       Embodiment 6 
       [0121]      FIG. 44  is a cross-sectional view of a semiconductor assembly in accordance with the sixth embodiment of the present invention. 
         [0122]    The semiconductor assembly  610  is similar to that illustrated in  FIG. 37 , except that (i) the stacked semiconductor sub-assembly  20  further includes a passive component  23  electrically coupled to the routing circuitry  21  and encapsulated in the molding compound  25 , and (ii) the first wiring structure  31  of the wiring board  30  has a larger thickness to create a deeper cavity  316 , and the routing circuitry  21  and the second device  27  of the stacked semiconductor sub-assembly  20  also extend into the cavity  316  of the wiring board  30 . 
         [0123]      FIG. 45  is a cross-sectional view of the semiconductor assembly  610  of  FIG. 44  further provided with a third device  61  at the first wiring structure  31  and solder balls  73  at the second wiring structure  36 . The third device  61  is stacked over the stacked semiconductor sub-assembly  20  and the wiring board  30  and electrically coupled to the first wiring structure  31  through solder balls  71 . The solder balls  73  are mounted on and electrically coupled to the second wiring structure  36  for external connection. 
         [0124]      FIG. 46  is a cross-sectional view of the semiconductor assembly  610  of  FIG. 44  further provided with a lens  88  at the first wiring structure  31  and solder balls  73  at the second wiring structure  36 . The lens  88  optically transparent to at least one range of light wavelengths is stacked over the stacked semiconductor sub-assembly  20  and mounted to the first wiring structure  31 . The solder balls  73  are mounted on and electrically coupled to the second wiring structure  36  for external connection. 
         [0125]    The semiconductor assemblies described above are merely exemplary. Numerous other embodiments are contemplated. In addition, the embodiments described above can be mixed-and-matched with one another and with other embodiments depending on design and reliability considerations. For instance, the first wiring structure may have multiple through openings in an array and each stacked semiconductor sub-assembly is accommodated in its corresponding through opening. Also, the first wiring structure of the wiring board can include additional conductive traces to receive and route additional stacked semiconductor sub-assemblies. 
         [0126]    As illustrated in the aforementioned embodiments, a distinctive semiconductor assembly is configured and includes a stacked semiconductor sub-assembly electrically coupled to a wiring board by bonding wires. Optionally, an encapsulant may be further provided to cover the bonding wires. For the convenience of below description, the direction in which the first surfaces of the routing circuitry and the first wiring structure face is defined as the first direction, and the direction in which the second surfaces of the routing circuitry and the first wiring structure faces is defined as the second direction. 
         [0127]    The stacked semiconductor sub-assembly includes a first device, a second device, a routing circuitry and optionally a molding compound, and may be prepared by the steps of: electrically coupling the first device to the first surface of the routing circuitry detachably adhered over a sacrificial carrier by, for example, bumps; optionally providing the molding compound over the routing circuitry; removing the sacrificial carrier from the routing circuitry; and electrically coupling the second device to the second surface of the routing circuitry by, for example, bumps or bonding wires. As a result, the first and second devices, respectively disposed over the first and second surfaces of the routing circuitry, can be electrically connected to each other by the routing circuitry. 
         [0128]    The first and second devices can be semiconductor chips, packaged devices, or passive components. The first device can be electrically coupled to the routing circuitry by a well-known flip chip bonding process with its active surface facing in the routing circuitry using bumps without metallized vias in contact with the first device. Likewise, after removal of the sacrificial carrier, the second device can be electrically coupled to the routing circuitry by a well-known flip chip bonding process with its active surface facing in the routing circuitry using bumps without metallized vias in contact with the second device. Alternatively, the second device is electrically coupled to the routing circuitry by wire bonding process with its active surface facing away the routing circuitry. 
         [0129]    The routing circuitry can be a buildup circuitry without a core layer to provide primary fan-out routing/interconnection and the shortest interconnection distance between the first and second devices. Preferably, the routing circuitry is a multi-layered buildup circuitry and can include at least one dielectric layer and conductive traces that fill up via openings in the dielectric layer and extend laterally on the dielectric layer. The dielectric layer and the conductive traces are serially formed in an alternate fashion and can be in repetition when needed. Accordingly, the routing circuitry can be formed with electrical contacts at its first and second surfaces for first device connection from the first surface and second device connection and next-level connection from the second surface. 
         [0130]    The wiring board includes a heat spreader, a first wiring structure and a second wiring structure. The first wiring structure includes electrical contacts at its second surface for the routing circuitry connection from the second direction, whereas the second wiring structure includes electrical contacts at its exterior surface for next-level connection from the first direction. The first wiring structure has a through opening extending from its first surface to its second surface to accommodate the heat spreader and the stacked semiconductor sub-assembly therein. The first wiring structure is not limited to a particular structure, and may be a multi-layered routing circuitry that laterally surround peripheral edges of the first device, the optional molding material and the heat spreader. For instance, the first wiring structure may include an interconnect substrate, a first buildup circuitry and a second buildup circuitry. The first and second buildup circuitries are disposed on both opposite sides of the interconnect substrate. The interconnect substrate can include a core layer, first and second routing layers respectively on both opposite sides of the core layer, and metallized through vias formed through the core layer to provide electrical connection between the first and second routing layers. Each of the first and second buildup circuitries typically includes a dielectric layer and one or more conductive traces. The dielectric layers of the first and second buildup circuitries are respectively deposited on opposite sides of the interconnect substrate. The conductive traces extend laterally on the dielectric layer and include conductive vias in contact with first and second routing layers of the interconnect substrate. Further, the first and second buildup circuitries can include additional dielectric layers, additional via openings, and additional conductive traces if needed for further signal routing. Accordingly, the outmost conductive traces at both the first and second surfaces of the first wiring structure can provide electrical contacts for the routing circuitry connection from its second surface and for the second wiring structure connection from its first surface. The second wiring structure is provided to cover the backside surface of the heat spreader and the first surface of the first wiring structure, and is electrically coupled to the heat spreader and the first wiring structure by metallized vias embedded in a dielectric layer of the second wiring structure and in contact with the backside surface of the heat spreader and the first surface of the first wiring structure. Accordingly, the heat spreader, covered by the dielectric layer of the second wiring structure from the first direction, can be mechanically supported by the second wiring structure and provide thermal dissipation and EMI shielding for the first device attached thereto using a thermally conductive material. As the heat spreader has a thickness less than that of the first wiring structure, a cavity is formed in the wiring board to accommodate the stacked semiconductor sub-assembly therein. Preferably, the heat spreader is a metal layer having peripheral edges adjacent to and attached to sidewalls of the through opening of the first wiring structure. Optionally, an additional metal layer may be further provided in contact with the heat spreader and the sidewalls of the through opening of the first wiring structure and completely cover a remaining portion of sidewalls of the through opening of the first wiring structure. The second wiring structure may be a multi-layered routing circuitry and laterally extends to peripheral edges of the first wiring structure. Preferably, the second wiring structure is a multi-layered buildup circuitry without a core layer, and includes dielectric layers and conductive traces in repetition and alternate fashion. The conductive traces include metallized vias in the dielectric layer and extend laterally on the dielectric layer. The outmost conductive traces of the first and second wiring structures can respectively accommodate conductive joints, such as solder balls or bonding wires, for electrical communication and mechanical attachment with an assembly, an electronic device, an additional heat spreader, an additional wiring board or others. For instance, a third device may be a semiconductor chip and mounted over and electrically coupled to the second wiring structure through a plurality of bonding wires, or be a ball grid array package or a bumped chip and mounted over and electrically coupled to the first wiring structure or the second wiring structure through a plurality of solder balls. As another aspect of the present invention, an additional heat spreader may be mounted over the second surface of the first wiring structure, and the second device can be disposed in a cavity of the additional heat spreader and thermally conductible to the additional heat spreader through a thermally conductive material. Further, the additional heat spreader may be electrically coupled to the first wiring structure for ground connection by, for example, solder balls in contact with the additional heat spreader and the outmost conductive traces of the first wiring structure. Alternatively, an additional wiring board may be stacked over the stacked semiconductor sub-assembly and the wiring board and electrically coupled to the first wiring structure from the second surface of the first wiring structure. More specifically, the additional wiring board can include a third wiring structure, a fourth wiring structure and an additional heat spreader. The third wiring structure has a through opening extending from its first surface to its second surface to accommodate the additional heat spreader and the second device therein. Preferably, the third wiring structure is a multi-layered routing circuitry and laterally surround peripheral edges of the additional heat spreader and a selected portion of the sub-assembly outside of the through opening. For instance, the third wiring structure may include an interconnect substrate having a core layer, routing layers respectively on both opposite sides of the core layer, and metallized through vias formed through the core layer to provide electrical connection between both the routing layers. Alternatively, the third wiring structure may be a multi-layered buildup circuitry without a core layer, and includes dielectric layers and conductive traces in repetition and alternate fashion. In any case, the third wiring structure can include electrical contacts at its opposite first and second surfaces for electrical connection with the first wiring structure and with the fourth wiring structure. Accordingly, the third wiring structure can be electrically coupled to the first wiring structure by, for example, solder balls, between the second surface of the first wiring structure and the first surface of the third wiring structure, whereas the fourth wiring structure can be electrically coupled to the second surface of the third wiring structure by metallized vias. Further, the fourth wiring structure is also electrically coupled to the heat spreader disposed in the through opening of the third wiring structure by metallized vias for ground connection. As a result, when the second device of the sub-assembly is disposed in the through opening of the third wiring structure, the heat spreader of the additional wiring board can provide thermal dissipation and EMI shielding for the second device attached thereto using a thermally conductive material. Preferably, the fourth wiring structure is a multi-layered routing circuitry and laterally extends to peripheral edges of the third wiring structure. For instance, the fourth wiring structure may be a multi-layered buildup circuitry without a core layer, and include dielectric layers and conductive trace in repetition and alternate fashion. As a result, the fourth wiring structure can include conductive traces at its exterior surface to provide electrical contacts from the second direction, and a third device may be optionally stacked over and electrically coupled to the exterior surface of the fourth wiring structure. Additionally, when the stacked semiconductor sub-assembly is an optical sub-assembly, a lens optically transparent to at least one range of light wavelengths may be stacked over the sub-assembly and mounted on the first wiring structure of the wiring board. 
         [0131]    The bonding wires provide electrical connections between the routing circuitry of the sub-assembly and the first wiring structure of the wiring board. In a preferred embodiment, the bonding wires contact and are attached to the second surface of the routing circuitry exposed from the through opening of the first wiring structure and the second surface of the first wiring structure. As a result, the first and second devices can be electrically connected to the wiring board for external connection through the routing circuitry and the bonding wires. 
         [0132]    Optionally, an array of vertical connecting elements may be further provided in electrical connection with the wiring board for next-level connection. Preferably, the vertical connecting elements contact and are electrically coupled to the first wiring structure from the second surface of the first wiring structure. The vertical connecting elements can include metal posts, solder balls or others, and may be laterally covered by an encapsulant. As the vertical connecting elements have a selected portion not covered by the encapsulant, a third device can be further provided to be electrically coupled to the vertical connecting elements. 
         [0133]    The term “cover” refers to incomplete or complete coverage in a vertical and/or lateral direction. For instance, in a preferred embodiment, the heat spreader covers the first device in the first direction regardless of whether another element such as the thermally conductive material is between the first device and the heat spreader. 
         [0134]    The phrases “attached to”, “attached on”, “mounted to” and “mounted on” includes contact and non-contact with a single or multiple element(s). For instance, in a preferred embodiment, the peripheral edges of the heat spreader are attached to the sidewalls of the through opening regardless of whether the peripheral edges of the heat spreader contact the sidewalls of the through opening or are separated from the sidewalls of the through opening by an adhesive. 
         [0135]    The phrases “electrical connection”, “electrically connected” and “electrically coupled” refer to direct and indirect electrical connection. For instance, in a preferred embodiment, the bonding wires directly contact and are electrically connected to the first wiring structure, and the routing circuitry is spaced from and electrically connected to the first wiring structure by the bonding wires. 
         [0136]    The “first direction” and “second direction” do not depend on the orientation of the semiconductor assembly, as will be readily apparent to those skilled in the art. For instance, the first surfaces of the routing circuitry and the first wiring structure face the first direction and the second surfaces of the routing circuitry and the first wiring structure face the second direction regardless of whether the semiconductor assembly is inverted. Thus, the first and second directions are opposite one another and orthogonal to the lateral directions. Furthermore, the first direction is the upward direction and the second direction is the downward direction when the outer surface of the second wiring structure faces in the upward direction, and the first direction is the downward direction and the second direction is the upward direction when the outer surface of the second wiring structure faces in the downward direction. 
         [0137]    The semiconductor assembly according to the present invention has numerous advantages. For instance, the first and second devices are mounted on opposite sides of the routing circuitry, which can offer the shortest interconnect distance between the first and second devices. The routing circuitry provides primary fan-out routing/interconnection for the first and second devices, whereas the wiring board provides a second level fan-out routing/interconnection. As the routing circuitry of the sub-assembly are connected to the first wiring structure of the wiring board by bonding wires, not by direct build-up process, the simplified process steps result in lower manufacturing cost. The heat spreader can provide thermal dissipation, electromagnetic shielding and moisture barrier for the first device. The second wiring structure can provide mechanical support for the heat spreader and dissipate heat from the heat spreader. The semiconductor assembly made by this method is reliable, inexpensive and well-suited for high volume manufacture. 
         [0138]    The manufacturing process is highly versatile and permits a wide variety of mature electrical and mechanical connection technologies to be used in a unique and improved manner. The manufacturing process can also be performed without expensive tooling. As a result, the manufacturing process significantly enhances throughput, yield, performance and cost effectiveness compared to conventional techniques. 
         [0139]    The embodiments described herein are exemplary and may simplify or omit elements or steps well-known to those skilled in the art to prevent obscuring the present invention. Likewise, the drawings may omit duplicative or unnecessary elements and reference labels to improve clarity.