Abstract:
A semiconductor package is provided, including: a substrate; a first semiconductor element disposed on the substrate and having a first conductive pad grounded to the substrate; a conductive layer formed on the first semiconductor element and electrically connected to the substrate; a second semiconductor element disposed on the first semiconductor element through the conductive layer; and an encapsulant formed on the substrate and encapsulating the first and second semiconductor elements. Therefore, the first and second semiconductor elements are protected from electromagnetic interference (EMI) shielding with the conductive layer being connected to the grounding pad of the substrate. A fabrication method of the semiconductor package is also provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to semiconductor packages, and, more particularly, to a semiconductor package having an EMI shielding function and a fabrication method thereof. 
         [0003]    2. Description of Related Art 
         [0004]    With the development of electronic industry, electronic products at the market have demands for light weight, compact, high performance and multi functions. A semiconductor package inside a product thereby is developed toward to high computation speed, high element density and high complexity, and is further integrated with electronic components having other biological, optical, mechanical, electrical, magnetic and the like functions into the same die. 
         [0005]    In order to correspond the trend of compact semiconductor package, system in package (SiP) develops a package structure of stacked die. However, the structure increases the element density, and results the electromagnetic interference (EMI) between a top die and a bottom die. 
         [0006]    In order to solve the EMI problem between the top and bottom dies, the prior art forms a metal layer on the bottom face of the top die by a sputtering method. Therefore the metal layer is between the top die and the bottom die, and the EMI shielding effect can be achieved after grounding the metal layer. 
         [0007]    Please refer to  FIG. 1 , which is a schematic cross sectional view of a semiconductor package  1  according to the prior art. As shown in  FIG. 1 , the semiconductor package  1  comprises: a substrate  10  having a grounding pad  100 ; a first semiconductor element  11  disposed and electrically connected through a conductive bump to the substrate  10 ; a second semiconductor element  13  with a sputtered metal layer  12 , wherein the second semiconductor element  13  is disposed on the first semiconductor element  11  by the side of the metal layer  12 , and the metal layer  12  is connected to the grounding pad  100  on the substrate  10 ; and an encapsulant  14  formed on the substrate  10  such that the first semiconductor element  11  and the second semiconductor element  13  are encapsulated in the encapsulant  14 . 
         [0008]    However, the metal layer  12  is formed by a sputtering method to achieve the EMI shielding effect, which is complicated and costly. 
         [0009]    Therefore, how to overcome the EMI problem of the prior art is substantially an issue desirably to be solved in the industry. 
       SUMMARY OF THE INVENTION 
       [0010]    In view of the problems of the above-mentioned prior art, the present invention provides a semiconductor package, comprising: a substrate; a first semiconductor element disposed on the substrate and having a first conductive pad grounded to the substrate; a conductive layer formed on the first semiconductor element and electrically connected to the first conductive pad; a second semiconductor element disposed on the conductive layer; and an encapsulant formed on the substrate and encapsulating the first and second semiconductor elements. 
         [0011]    The present invention further provides a fabrication method of the semiconductor package, comprising: providing a substrate; disposing on the substrate a first semiconductor element having a first conductive pad; grounding the first conductive pad and the substrate; forming on the first semiconductor element a conductive layer electrically connected to the first conductive pad; disposing a second semiconductor element on the conductive layer; and forming on the substrate an encapsulant encapsulating the first and second semiconductor elements. 
         [0012]    In an embodiment, the first conductive pad is grounded to the substrate by bonding wires. 
         [0013]    In an embodiment, the first semiconductor element has a redistribution layer formed on the first conductive pad, the conductive layer is disposed on the redistribution layer, and the redistribution layer electrically connects the first conductive pad to the conductive layer and is grounded to the substrate. In an embodiment, the redistribution layer has a conductive land electrically connected to the first conductive pad, and the conductive land is grounded to the substrate by bonding wires. 
         [0014]    In an embodiment, the first semiconductor element has a redistribution layer, and the redistribution layer has the first conductive pad. 
         [0015]    The present invention further provides a semiconductor package, comprising: a substrate; a first semiconductor element disposed on the substrate and having a first conductive pad and a second conductive pad connected to the first conductive pad and grounded to the substrate; a conductive layer formed on the first semiconductor element and electrically connected to the first conductive pad; a second semiconductor element disposed on the conductive layer; and an encapsulant formed on the substrate and encapsulating the first and second semiconductor elements. 
         [0016]    The present invention further provides a fabrication method of the semiconductor package, comprising: providing a substrate; disposing on the substrate a first semiconductor element having a first conductive pad and a second conductive pad connected to the first conductive pad; grounding the second conductive pad and the substrate; forming on the first semiconductor element a conductive layer electrically connected to the first conductive pad; disposing a second semiconductor element on the conductive layer; and forming on the substrate an encapsulant encapsulating the first and second semiconductor elements. 
         [0017]    In an embodiment, the first conductive pad is electrically connected to the second conductive pad by bonding wires. In an embodiment, the first semiconductor element has an internal circuit, and the first conductive pad is electrically connected to the second conductive pad by the internal circuit. 
         [0018]    In an embodiment, the substrate has a grounding pad for being grounded. 
         [0019]    In an embodiment, the second semiconductor element is electrically connected to the substrate. 
         [0020]    In an embodiment, the conductive layer is made of a conductive adhesive. 
         [0021]    In an embodiment, an electrical element is further disposed on the substrate and grounded to the substrate and the first semiconductor element. 
         [0022]    From the above, in the semiconductor package and fabrication methods thereof according to the present invention, the EMI shielding effect is achieved by disposing a conductive layer between a first semiconductor element and a second semiconductor to prevent EMI between semiconductor elements. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0023]    The invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein: 
           [0024]      FIG. 1  is a schematic sectional view illustrating a structure of a prior semiconductor package according to the prior art; 
           [0025]      FIGS. 2A-2D  are schematic sectional views of a fabrication method of a semiconductor package of a first embodiment according to the present invention, wherein FIG.  2 A′ is a top view of  FIG. 2A , FIG.  2 B′ is a top view of  FIG. 2B , and FIG.  2 C′ is a top view of  FIG. 2C ; 
           [0026]    FIGS.  3  and  3 ′ are a schematic sectional view and a top view of a semiconductor package of a second embodiment according to the present invention, wherein FIG.  3 ′ is the top view of  FIG. 3 ; 
           [0027]    FIGS.  4  and  4 ′ are a schematic sectional view and a top view of a semiconductor package of a third embodiment according to the present invention, wherein FIG.  4 ′ is the top view of  FIG. 4 ; 
           [0028]      FIG. 5  is a schematic sectional view of a semiconductor package of a fourth embodiment according to the present invention; 
           [0029]      FIG. 6  is a schematic sectional view of a semiconductor package of a fifth embodiment according to the present invention; and 
           [0030]      FIG. 7  is a schematic sectional view of a semiconductor package of a sixth embodiment according to the present invention; 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparently understood by those in the art after reading the disclosure of this specification. The present invention can also be performed or applied by other different embodiments. The details of the specification may be on the basis of different points and applications, and numerous modifications and variations can be devised without departing from the spirit of the present invention. 
         [0032]    It should be advised that the structure, ratio, and size as illustrated in this context are only used for disclosures of this specification, provided for persons skilled in the art to understand and read, and technically do not have substantial meaning. Any modification of the structure, change of the ratio relation, or adjustment of the size should be involved in the scope of disclosures in this specification without influencing the producible efficacy and the achievable objective of this specification. Also, the referred terms such as “on”, “first”, “second” and “one” in this specification are only for the convenience to describe, not for limiting the scope of embodiment in this invention. Those changes or adjustments of relative relationship without substantial change of technical content should also be considered within the category of implementation. 
         [0033]      FIGS. 2A-2D  are schematic sectional views illustrating a fabrication method of a semiconductor package of a first embodiment according to the present invention, wherein FIG.  2 A′ is a top view of  FIG. 2A , FIG.  2 B′ is a top view of  FIG. 2B , and FIG.  2 C′ is a top view of  FIG. 2C . 
         [0034]    As shown in FIGS.  2 A and  2 A′, a substrate  20  having a plurality of grounding pads  200  and grounding vias  201  is provided, a first semiconductor element  21  is disposed on the substrate  20 , the first semiconductor element  21  has a plurality of first conductive pads  211  for being grounded the substrate  20 . 
         [0035]    In an embodiment, the first conductive pad  211  is electrically connected to the grounding pad  200  by bonding wires  25 , and the first semiconductor element  21  is a die or a packaged element. 
         [0036]    As shown in  FIG. 2B , a conductive layer  22  is formed on the first semiconductor element  21 , and the conductive layer  22  covers the first conductive pads  211 , and coats one end of each of the bonding wires  25  connected to the first conductive pads to electrically connects each of the first conductive pads  211 . 
         [0037]    In an embodiment, the first semiconductor element  21  also has other connecting pads  213 , and the conductive layer  22  does not cover the connecting pads  213 , as shown in FIG.  2 B′. 
         [0038]    Moreover, the conductive layer  22  is made of a conductive adhesive containing a metal material that can shield and block EMI to achieve the EMI shielding effect. 
         [0039]    As shown in  FIG. 2C , a second semiconductor element  23  is disposed on the conductive layer  22 , and stacked on the first semiconductor element  21 . The second semiconductor element  23  is electrically connected to the substrate  20  by bonding wires  25 . 
         [0040]    In an embodiment, the second semiconductor element  23  is a die or a packaged element. 
         [0041]    As shown in  FIG. 2D , an encapsulant  24  is formed on the substrate  20  to encapsulate the first semiconductor element  21  and the second semiconductor element  23  to fabricate a semiconductor package  2  according to the present invention. 
         [0042]    In an embodiment, forming methods and materials of the encapsulant  24  is adaptable for persons skilled in the art, and thus will not described herein. 
         [0043]    In a second embodiment shown in FIGS.  3  and  3 ′, the first semiconductor element  21  further has a second conductive pad  212  electrically connected to the first conductive pad  211 , and the second conductive pad  212  is electrically connected to the substrate  20  by bonding wires  25 , wherein the first conductive pad  211  is electrically connected to the second conductive pad  212  by bonding wires  25 . 
         [0044]    In a third embodiment shown in FIGS.  4  and  4 ′, the first semiconductor element  21  further has an internal circuit  210  to electrically connect the first conductive pad  211  to the second conductive pad  212 . 
         [0045]    In a fourth embodiment shown in  FIG. 5 , the first semiconductor element  21  has a redistribution layer  30  on the first conductive pad  211 , the conductive layer  22  is disposed and electrically connected to the redistribution layer  30 , and the redistribution layer  30  has conductive lands  300   a ,  300   b  electrically connected to the first conductive pad  211 . A portion of the electrical contact  300   b  is grounded to the substrate by bonding wires  25 . 
         [0046]    In a fifth embodiment shown in  FIG. 6 , the interconnected first conductive pad  211 ′ and second conductive pad  212 ′ may be formed in the redistribution layer  30 ′. 
         [0047]    The present invention utilizes the design of conductive layer  22  to effectively conduct remaining electricity out to the substrate  20  for grounding such that to overcome the EMI problem between the first semiconductor element  21  and the second semiconductor element  23 . The semiconductor package  2 ,  3 ,  4 ,  5 ,  6  according to the present invention thereby have better EMI shielding effect. 
         [0048]    As shown in  FIG. 7 , an electronic element  7  is additionally disposed on the substrate  20  of the semiconductor package  2 , and is grounded to the substrate  20  and the first conductive pad  211 . 
         [0049]    In an embodiment, the electronic element  7  is considered as a stacked die structure of a semiconductor package  4  shown in  FIG. 4 . The second conductive pad  72  of the electronic element  7  is for being grounded the substrate  20  and electrically connected to the first conductive pad  211  of the semiconductor package  2 , and the first conductive pad  71  of the electronic element  7  is electrically connected to the second conductive pad  72  of the electronic element  7  by an internal circuit  70 . 
         [0050]    The present invention provides a semiconductor package  2 ,  3 ,  4 ,  5 ,  6 , comprising: a substrate  20 , a first semiconductor element  21  disposed on the substrate  20 , a conductive layer  22  formed on the first semiconductor element  21 , a second semiconductor element  23  disposed on the conductive layer  22 , and an encapsulant  24  formed on the substrate  20 . 
         [0051]    The substrate  20  has a plurality of grounding pads  200 . 
         [0052]    The first semiconductor element  21  has a plurality of first conductive pads  211  grounded to the grounding pads  200  by bonding wires  25 . 
         [0053]    In an embodiment, the first semiconductor element  21  further has a second conductive pad  212  electrically connected to the first conductive pad  211  by bonding wires  25  or an internal circuit, and the second conductive pad  212  is electrically connected to the substrate  20  by bonding wires  25 . 
         [0054]    The conductive layer  22  is electrically connected to the first conductive pad  211 . 
         [0055]    In an embodiment, the conductive layer  22  is made of a conductive adhesive. 
         [0056]    The second semiconductor element  22  is electrically connected to the substrate  20 . 
         [0057]    The encapsulant  24  encapsulates the first and second semiconductor elements  21 ,  22 . 
         [0058]    In an embodiment, the first semiconductor element  21  has a redistribution layer  30  on the first conductive pad  211 , and the conductive  22  is disposed on the redistribution layer  30  to electrically connect the first conductive pad  211  to the conductive layer and ground to the substrate  20 . In an embodiment, the redistribution layer  30  further has conductive lands  300   a ,  300   b  electrically connected to the first conductive pad  211 , and the conductive land  300   b  is grounded to the substrate  20  by bonding wires  25 . 
         [0059]    In an embodiment, a redistribution layer  30 ′ has the conductive pad  211 ′. 
         [0060]    In summary, the semiconductor package and fabrication methods thereof according to the present invention overcome the drawback of generating EMI while using a stacked die structure in the prior semiconductor package by a design of conductive layer. Advantages such as simple process, low cost and various applications are provided. 
         [0061]    The foregoing descriptions of the detailed embodiments are only illustrated to disclose the features and functions of the present invention and not restrictive of the scope of the present invention. It should be understood to those in the art that all modifications and variations according to the spirit and principle in the disclosure of the present invention should fall within the scope of the appended claims.