Abstract:
A method for fabricating a semiconductor package is provided, which includes the steps of: providing a first substrate having a plurality of first conductive posts on a surface thereof and providing a second substrate having a third surface having a chip disposed thereon and a fourth surface opposite to the third surface; disposing the first substrate on the third surface of the second substrate through the first conductive posts; forming an encapsulant between the first substrate and the second substrate, wherein the encapsulant has a first surface adjacent to the first substrate and a second surface opposite to the first surface; and removing the first substrate, thereby effectively preventing solder bridging from occurring.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to semiconductor packages and fabrication methods thereof, and more particularly, to a semiconductor package and a fabrication method thereof applicable to package on package (PoP) structures. 
         [0003]    2. Description of Related Art 
         [0004]    In recent years, to meet the miniaturization requirement of electronic products, PoP type packages have become an R&amp;D focus since they facilitate to save planar area of substrates while maintaining good processing performances. 
         [0005]      FIG. 1  is a schematic cross-sectional view of a conventional PoP type package. Referring to  FIG. 1 , a plurality of solder balls  11  are provided to serve as an interconnection structure for electrically connecting a lower packaging substrate  12  and an upper packaging substrate  13 . However, as the I/O density of the package increases, if the size of the package does not change, the pitch between the solder balls  11  must be reduced. As such, solder bridging easily occurs between the solder balls  11 . 
         [0006]    Therefore, there is a need to provide a semiconductor package and a fabrication method thereof so as to overcome the above-described drawbacks. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the above-described drawbacks, the present invention provides a method for fabricating a semiconductor package, which comprises the steps of: providing a first substrate having a plurality of first conductive posts on a surface thereof and a second substrate having a third surface having a chip disposed thereon and a fourth surface opposite to the third surface, and disposing the first substrate on the third surface of the second substrate through the first conductive posts; forming an encapsulant between the first substrate and the second substrate, wherein the encapsulant has a first surface adjacent to the first substrate and a second surface opposite to the first surface; and removing the first substrate. 
         [0008]    In the above-described method, the third surface of the second substrate can further have a plurality of conductive pads that are correspondingly electrically connected to the first conductive posts so as to dispose the first substrate on the second substrate. The first substrate can have a dielectric layer, a first metal layer and a second metal layer sequentially stacked, and the first conductive posts are formed on the second metal layer. 
         [0009]    In the above-described method, removing the first substrate can comprise removing the dielectric layer and the first metal layer first and then removing the second metal layer. A plurality of conductive elements can further be formed on top ends of the first conductive posts. A plurality of second conductive posts can further be formed on the conductive pads and correspondingly electrically connected to the first conductive posts. A plurality of conductive elements can further be formed on top ends of the second conductive posts. 
         [0010]    After removing the first substrate, the method can further comprise forming an OSP (Organic Solderability Preservative) layer on the first conductive posts. After removing the first substrate, the method can further comprise forming a plurality of conductive elements on the fourth surface of the second substrate. 
         [0011]    In the above-described method, the second substrate can have a first carrier and an adhesive layer sequentially stacked such that the first substrate is disposed on the second substrate with the first conductive posts attached to the adhesive layer, and after removing the first substrate, the method further comprises removing the second substrate so as to form a second redistribution layer on the second surface of the encapsulant. After removing the first substrate, the method can further comprise forming a first redistribution layer on the first surface of the encapsulant. 
         [0012]    After forming the first redistribution layer, the method can further comprise: disposing a second carrier on the first redistribution layer and removing the second substrate so as to form a second redistribution layer on the second surface of the encapsulant; and removing the second carrier. After forming the second redistribution layer, the method can further comprise forming a plurality of conductive elements on the second redistribution layer. 
         [0013]    The present invention further provides a semiconductor package, which comprises: an encapsulant having a first surface and a second surface opposite to the first surface; a chip embedded in the encapsulant and exposed from the second surface of the encapsulant; a plurality of conductive posts formed in the encapsulant and penetrating the first and second surfaces; a first redistribution layer formed on the first surface of the encapsulant and electrically connected to the conductive posts; and a second redistribution layer formed on the second surface of the encapsulant and electrically connected to the chip and the conductive posts. 
         [0014]    The above-described semiconductor package can further comprise a plurality of conductive elements formed on the second redistribution layer. 
         [0015]    Therefore, the prevent invention uses conductive posts to electrically connect upper and lower substrates. Since less space is consumed by the conductive posts compared with the conventional solder balls, the present invention meets the fine pitch requirement and prevents solder bridging from occurring. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a schematic cross-sectional view of a conventional PoP type package; 
           [0017]      FIGS. 2A to 2I  are schematic cross-sectional views showing a method for fabricating a semiconductor package according to a first embodiment of the present invention and an application example of the semiconductor package, wherein  FIG. 2B ′ shows another embodiment of  FIG. 2B ,  FIGS. 2C ′ and  2 C″ show other embodiments of  FIG. 2C  and  FIG. 2D ′ shows another embodiment of  FIG. 2D ; and 
           [0018]      FIGS. 3A to 3K  are schematic cross-sectional views showing a method for fabricating a semiconductor package according to a second embodiment of the present invention and an application example of the semiconductor package. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0019]    The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparent to those in the art after reading this specification. 
         [0020]    It should be noted that all the drawings are not intended to limit the present invention. Various modifications and variations can be made without departing from the spirit of the present invention. Further, terms such as “first”, “second” etc. are merely for illustrative purposes and should not be construed to limit the scope of the present invention. 
       First Embodiment 
       [0021]      FIGS. 2A to 2I  are schematic cross-sectional views showing a method for fabricating a semiconductor package according to a first embodiment of the present invention and an application example of the semiconductor package. 
         [0022]    Referring to  FIG. 2A , a first substrate  20  is provided, which has a dielectric layer  201 , a first metal layer  202  and a second metal layer  203  sequentially stacked. The dielectric layer  201  can be made of FR4, the first metal layer  202  can be a copper layer and the second metal layer  203  can be a copper foil. 
         [0023]    Referring to  FIG. 2B , a plurality of first conductive posts  204  are formed on the second metal layer  203  of the first substrate  20 . The first conductive posts  204  can be made of copper. In the present embodiment, a plurality of conductive elements  205  made of such as a solder material are further formed on top ends of the first conductive posts  204 . In another embodiment, referring to  FIG. 2B ′, the conductive elements  205  can be omitted. 
         [0024]    Referring to  FIG. 2C , a second substrate  21  is provided. The second substrate  21  can be, for example, a BT substrate, an FR-4 substrate or a ceramic substrate. The second substrate  21  has a third surface  21   a  and a fourth surface  21   b  opposite to the third surface  21   a.  A chip  22  is disposed on the third surface  21   a.  Further, the third surface  21   a  has a plurality of conductive pads  211 . Further, referring to  FIG. 2C ′, a plurality of second conductive posts  212  can be formed on the conductive pads  211 . Furthermore, referring to  FIG. 2C ″, a plurality of conductive elements  213  made of such as a solder material can be formed on the second conductive posts  212 . 
         [0025]    Referring to  FIG. 2D , the first substrate  20  is disposed on the second substrate  21  by correspondingly electrically connecting the first conductive posts  204  to the conductive pads  211 . In another embodiment, referring to  FIG. 2D ′, the first conductive posts  204  are correspondingly electrically connected to the second conductive posts  212 . 
         [0026]    Referring to  FIG. 2E , continued from  FIG. 2D , an encapsulant  23  is formed between the first substrate  20  and the second substrate  21 . The encapsulant  23  has a first surface  23   a  adjacent to the first substrate  20  and a second surface  23   b  opposite to the first surface  23   a.    
         [0027]    Referring to  FIG. 2F , the dielectric layer  201  and the first metal layer  202  are removed by such as peeling. 
         [0028]    Referring to  FIG. 2G , the second metal layer  203  is removed by such as etching to expose the first conductive posts  204 . If needed, an OSP (Organic Solderability Preservative) layer (not shown) can be formed on the first conductive posts  204 . 
         [0029]    Referring to  FIG. 2H , a plurality of conductive elements  24  are formed on the fourth surface  21   b  of the second substrate  21 , thereby forming a semiconductor package  2 . 
         [0030]    Referring to  FIG. 2I , an electronic element  25 , such as another semiconductor package or a semiconductor chip, is disposed on the semiconductor package  2  and electrically connected to the first conductive posts  204 . 
       Second Embodiment 
       [0031]      FIGS. 3A to 3K  are schematic cross-sectional views showing a method for fabricating a semiconductor package according to a second embodiment of the present invention and an application example of the semiconductor package. 
         [0032]    Referring to  FIG. 3A , a second substrate  30  is provided, which has a first carrier  301  and an adhesive layer  302  sequentially stacked. The second substrate  30  has a third surface  30   a  having at least a chip  22  disposed thereon and a fourth surface  30   b  opposite to the third surface  30   a.  The first carrier  301  can be made of glass or silicon and in a wafer or panel form. 
         [0033]    Referring to  FIG. 3B , a first substrate  20  is provided, which has a dielectric layer  201 , a first metal layer  202  and a second metal layer  203  sequentially stacked. The dielectric layer  201  can be made of FR4, the first metal layer  202  can be a copper layer and the second metal layer  203  can be a copper foil. A plurality of first conductive posts  204  are formed on the second metal layer  203  of the first substrate  20 . The first substrate  20  is disposed on the second substrate  20  with the first conductive posts  204  attached to the adhesive layer  302 . 
         [0034]    Referring to  FIG. 3C , an encapsulant  23  is formed between the first substrate  20  and the second substrate  30 . The encapsulant  23  has a first surface  23   a  adjacent to the first substrate  20  and a second surface  23   b  opposite to the first surface  23   a.    
         [0035]    Referring to  FIG. 3D , the dielectric layer  201  and the first metal layer  202  are removed by such as peeling. 
         [0036]    Referring to  FIG. 3E , the second metal layer  203  is removed by such as etching to expose the first conductive posts  204 . If needed, an OSP layer (not shown) can be formed on the first conductive posts  204 . 
         [0037]    Referring to  FIG. 3F , a first redistribution layer  31  is formed on the first surface  23   a  of the encapsulant  23 . 
         [0038]    Referring to  FIG. 3G , the second substrate  30  is removed. 
         [0039]    Referring to  FIG. 3H , if needed, a second carrier  32  is disposed on the first redistribution layer  31  through an adhesive layer  33 . 
         [0040]    Referring to  FIG. 3I , a second redistribution layer  34  is formed on the second surface  23   b.    
         [0041]    Referring to  FIG. 3J , a plurality of conductive elements  24  are formed on the second redistribution layer  34 , thereby forming a semiconductor package  3 . 
         [0042]    Referring to  FIG. 3K , an electronic element  25 , such as another semiconductor package or a semiconductor chip, is disposed on the semiconductor package  3  and electrically connected to the first conductive posts  204 . 
         [0043]    Referring to  FIG. 3J , the present invention further provides a semiconductor package, which has: an encapsulant  23  having a first surface  23   a  and a second surface  23   b  opposite to the first surface  23   a;  a chip  22  embedded in the encapsulant  23  and exposed from the second surface  23   b  of the encapsulant  23 ; a plurality of first conductive posts  204  formed in the encapsulant  23  and penetrating the first and second surfaces  23   a,    23   b;  a first redistribution layer  31  formed on the first surface  23   a  of the encapsulant  23  and electrically connected to the first conductive posts  204 ; and a second redistribution layer  34  formed on the second surface  23   b  of the encapsulant  23  and electrically connected to the chip  22  and the first conductive posts  204 . 
         [0044]    The above-described semiconductor package can further have a plurality of conductive elements  24  formed on the second redistribution layer  34 . 
         [0045]    According to the present invention, a plurality of conductive posts are formed to electrically connect upper and lower substrates and after an encapsulant is formed between the upper and lower substrates, the upper substrate is removed. Since less space is consumed by the conductive posts compared with the conventional solder balls, the present invention meets the fine pitch requirement and prevents solder bridging from occurring, thereby improving the product yield. 
         [0046]    The above-described descriptions of the detailed embodiments are only to illustrate the preferred implementation according to the present invention, and it is not to limit the scope of the present invention. Accordingly, all modifications and variations completed by those with ordinary skill in the art should fall within the scope of present invention defined by the appended claims.