Patent Publication Number: US-8524530-B2

Title: Flexible semiconductor package and method for fabricating the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Korean patent application number 10-2008-0098753 filed on Oct. 8, 2008, which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to semiconductor devices, and more particularly to a flexible semiconductor package and a method for fabricating the same. 
     Recent developments in semiconductor technology have resulted in semiconductor chips capable of both storing massive amounts of data and processing the data, and a semiconductor package including the semiconductor chip. 
     A typical semiconductor package includes a substrate, a semiconductor chip disposed on the substrate, a connection member for connecting the semiconductor chip and the substrate, and a molding member covering the semiconductor chip in order to protect the semiconductor chip from external impact. In order to provide sufficient protection from external impact, the molding member covering the semiconductor chip has high strength. 
     As the application of semiconductor packages has increased, efforts have been undertaken to develop a flexible semiconductor package capable of being deflected (e.g., curved or bent). 
     The flexible semiconductor package has a structure in which a semiconductor chip is mounted on a flexible substrate. 
     However, when a memory semiconductor chip is mounted on a flexible semiconductor package, the semiconductor chip of the flexible semiconductor package is frequently damaged. 
     The damage to the memory semiconductor chip mounted in a flexible semiconductor package is due to the memory semiconductor chip having a relatively large size when a data storing unit for storing data and a data processing unit for processing the data are disposed together in a single memory semiconductor chip. In general, in a flexible semiconductor package, when the size of the semiconductor chip is increased, the semiconductor chip is damaged more frequently when the substrate is deflected (i.e., curved or bent). 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention include a flexible semiconductor package capable of being deflected (e.g., curved or bent) as well as preventing damage to a semiconductor chip of the semiconductor package. 
     Also, embodiments of the present invention are directed to a method for fabricating the flexible semiconductor package. 
     In one aspect of the present invention, a flexible semiconductor package includes a flexible substrate; a data chip disposed over the flexible substrate and having a data storage unit for storing data and first bonding pads electrically connected with the data storage unit; a control chip disposed over the flexible substrate and having a data processing unit for processing the data in the data chip and second bonding pads electrically connected with the data processing unit; and wirings for electrically connecting the first bonding pads to the second bonding pads. 
     A plurality of the data chips may also be disposed in a matrix form over the flexible substrate. 
     The flexible semiconductor package may further include a first bump interposed between the first bonding pad and the wiring; and a second bump interposed between the second bonding pad and the wiring. 
     The wiring may include a first coupling recess for inserting the first bump therein to increase a contact area between the wiring and the first bump, and a second coupling recess for inserting the second bump therein to increase a contact area between the wiring and the second bump. 
     The flexible semiconductor package may further include a flexible protection member disposed over the flexible substrate to cover the data chip and the control chip and having an opening some portion of the wiring. 
     The flexible semiconductor package may further include a first stress absorption member interposed between the data chip and the flexible substrate; and a second stress absorption member interposed between the control chip and the flexible substrate. 
     In another aspect of the present invention, a method for fabricating a semiconductor package includes electrically connecting first bonding pads of a data chip having a data storage unit for storing data to wirings of a flexible substrate; electrically connecting second bonding pads of a control chip having a data processing unit for processing the data in the data chip to the wirings of the flexible substrate; and forming a flexible protection member for covering the data chip and the control chip over the flexible substrate. 
     At least two data chips may also be disposed in a matrix form over the flexible substrate. 
     The wiring and the first bonding pads may be electrically connected by a first bump, and the wiring and the second bonding pads may be electrically connected by a second bump. 
     The step of forming the protection member may also include a step of forming an opening for exposing some portion of the wiring. 
     The method may further include interposing a first stress absorption member between the data chip and the flexible substrate; and interposing a second stress absorption member between the control chip and the flexible substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view showing a flexible semiconductor package in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view taken along line I-I′ in  FIG. 1 . 
         FIGS. 3 through 5  are plan views shown for illustrating a method for fabricating a semiconductor package in accordance with an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
       FIG. 1  is a plan view showing a flexible semiconductor package in accordance with an embodiment of the present invention.  FIG. 2  is a cross-sectional view taken along line I-I′ in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a flexible semiconductor package  100  includes a flexible substrate  10 , a data chip  20 , a control chip  30  and wirings  40 . In addition, the flexible semiconductor package  100  further includes a protection member  50  and first and second stress absorption members  60 ,  70 . 
     The flexible substrate  10  contains a flexible material. The flexible substrate  10  has, for example, a flexible film shape with a thin thickness. 
     The data chip  20  is disposed over the flexible substrate  10 . In the present embodiment, a plurality of the data chips  20  is disposed over the flexible substrate  10 , and the data chips are disposed in matrix form. The data chips  20  are spaced apart from each other by a distance D. In the present embodiment, the data chips  20  are disposed in a form of a 3×2 matrix over the flexible substrate  10 . 
     The data chip  20  includes a data storage unit  22  for storing data and first bonding pads  24  electrically connected to the data storage unit  22 . In the present embodiment, the first bonding pads  24  are disposed along an edge of the face of the data chip  20  facing the flexible substrate  10  (hereinafter referred to as the “upper face”). Alternatively, the first bonding pads  24  may be disposed along multiple edges (for example, opposing edges) of the upper face of the data chip  20 . 
     While a data storage unit for storing data and a peripheral circuit unit having a peripheral circuit for inputting/outputting the data into/from the data storage unit are formed integrally with each other in a conventional memory semiconductor chip, the data chip  20  in accordance with the present embodiment includes the data storage unit  22  alone without a peripheral circuit unit. In the present embodiment, when the data chip  22  includes the data storage unit  22  alone without a peripheral circuit unit, the data chip  20  has a size much smaller than that of a conventional memory semiconductor chip. 
     In the present embodiment, it is impossible to input/output the data through the first bonding pads  24  with only the data chip  20 . 
     The control chip  30  is disposed over the flexible substrate  10 . The control chip  30  can be disposed, for example, on the same face of the flexible substrate  10  as the face over which the data chip  20  is formed (that is, the face of the flexible substrate that faces the upper face of data chip  20  as shown in  FIG. 2 ). Alternatively, the control chip  30  can be disposed on the face of the flexible substrate  10  that opposes the face over which the data chip  20  is formed. 
     In an exemplary embodiment of the present invention, the control chip  30  can be disposed between the data chips  20 . The number of the control chip can be at least one, and in the present embodiment shown in  FIG. 1 , the control chip  30  is disposed in 3×1 matrix form between the data chips  20 . 
     Each control chip  30  includes a data processing unit  32  for controlling the data storage unit  22  of the data chip  20  to generate a control signal for inputting/outputting the data into/form the data chip  20 , and second bonding pads  34  electrically connected to the data processing unit  32 . In the present embodiment, the second bonding pads  34  can be disposed along an edge of an upper face of the control chip  30  which faces to the flexible substrate  10 . 
     In the present embodiment, the respective control chips  30  do not include a data storage unit. Since the control chips  30  do not include the data storage unit, the respective control chips  30  has a very small size when compared to a conventional memory semiconductor chip having a data storage unit and a data processing unit together. In the present embodiment, each control chip  30  can have, for example, a size smaller than the size of the data chip  20 . 
     Wirings  40  are disposed over the flexible substrate  10 . The wirings  40  include a first wiring  42 , a second wiring  44  and a third wiring  46 . 
     A first end of the first wiring  42  is electrically connected to the first bonding pad  24  of the data chip  20  and a second end opposite to the first end is electrically connected to the second bonding pad  34  of the control chip  30 . 
     A first end of the second wiring  44  is electrically connected to the second bonding pad  34  of the control chip  30  and a second end opposite to the first end is electrically connected to the second bonding pad  34  of the adjacent control chip  30 . 
     A first end of the third wiring  46  is electrically connected to the second bonding pad  34  of the control chip  30  and a second end opposite to the first end is disposed over the flexible substrate  10 . Pads  48  are disposed at the second end of the third wiring  46 . 
     Referring to  FIG. 2 , the wiring  40  and the first bonding pad  24  of the data chip  20  can be electrically connected by a first bump  26 . Also, the wiring  40  and the second bonding pad  34  of the control chip  30  can be electrically connected by a second bump  36 . 
     In the present embodiment, when deflection is generated in the flexible substrate  10 , a large shear stress is applied to the first bump  26  for connecting the first bonding pad  24  of the data chip  20  to the wiring  40 , since less deflection is generated in the data chip  20  as compared to the flexible substrate  10 . In the present embodiment, a first stress absorption member  60  is interposed between the flexible substrate  10  and the data chip  20  to reduce the shear stress applied to the first bump  26 . The first stress absorption member  60  functions to reduce the shear stress applied to the first bump  26  as well as to firmly secure the data chip  20  to the flexible substrate  10 . 
     Also, when the deflection is generated in the flexible substrate  10 , a large shear stress is applied to the second bump  36  connecting the second bonding pad  34  of the control chip  30  to the wiring  40 , since less deflection is generated in the control chip  30  as compared to the flexible substrate  10 . In the present embodiment, a second stress absorption member  70  is interposed between the flexible substrate  10  and the control chip  30  to reduce the shear stress applied to the second bump  36 . The second stress absorption member  70  functions to reduce the shear stress applied to the second bump  36  as well as to firmly secure the control chip  30  to the flexible substrate  10 . 
     Meanwhile, in order to efficiently absorb the shear stress applied to the first bump  26 , the wiring  40  connected to the first bump  26  can be formed with a recess or a hole for inserting the first bump  26  therein. When the first bump  26  is inserted in the recess or hole of the wiring  40 , a contact area between the first bump  26  and the wiring  40  is increased to thereby prevent the first bump  26  from being separated from the wiring  40  by the shear stress. 
     Also, in order to efficiently absorb the shear stress applied to the second bump  36 , the wiring  40  connected to the second bump  36  can be formed with a recess or a hole for inserting the second bump  36  therein. When the second bump  36  is inserted in the recess or hole of the wiring  40 , a contact area between the second bump  36  and the wiring  40  is increased to thereby prevent the second bump  36  from being separated from the wiring  40  by the shear stress. 
     Referring to  FIG. 2 , a flexible protection member  50  can be disposed over the flexible substrate  10 . The protection member  50  can be a flexible organic layer and the protection member  50  is formed with an opening for exposing the pads  48 . The protection member  50  prevents the data chip  20  and/or the control chip  30  from being damaged by external impact and/or contaminated. 
       FIGS. 3 through 5  are plan views shown for illustrating a method for fabricating a semiconductor package in accordance with an embodiment of the present invention. 
     Referring to  FIG. 3 , in order to fabricate a flexible semiconductor package, a flexible substrate  10  is prepared. 
     The flexible substrate  10  has a flexible film shape and wirings  40  are formed over the upper face of the flexible substrate  10 . 
     In order to form the wirings  40 , a metal layer is formed over the flexible substrate  10  and the metal layer is patterned by a photolithography process. Therefore, the wirings  40  include a first wiring  42 , a second wiring  44  and a third wiring  46  that are formed over the flexible substrate  10 . 
     The first wiring  42  electrically connects a data chip to a control chip (which will be described later), the second wiring  44  electrically connects adjacent control chips  30 , and a first end of the third wiring  46  is electrically connected to the control chip. Pads are formed at a second end of the third wiring  46  that is opposite to the first end. 
     A first stress absorption member  60  is disposed in a portion of the flexible substrate  10  where the data chip to be described later is to be attached, and a second stress absorption member  70  is disposed in a portion of the flexible substrate  10  where the control chip to be described later is to be attached. When deflection is generated in the flexible substrate having attached thereon the data chip and the control chip (described layer), the first and second stress absorption members  60 ,  70  absorb a bending stress or a shear stress applied to the data chip and the control chip so as to prevent damage of the data chip and the control chip as well as prevent separation of the control chip and the wiring and separation of the data chip and the wiring. 
     Referring to  FIG. 4 , after the flexible substrate  10  is prepared, the data chip  20  is attached onto the first stress absorption member  60  of the flexible substrate  10 . The data chip  20  includes a data storage unit  22  for storing data, but the data chip  20  does not include a data processing unit for inputting/outputting the data contained in the data storage unit  22 . Therefore, the data chip  20  has a relatively small size when compared to a conventional memory semiconductor chip having the data storage unit and the data processing unit together. 
     The data chip  20  includes first bonding pads  24  as shown in  FIG. 2 , and the first bonding pads  24  are electrically connected with the wiring  40 , for example, via a first bump  26 . Alternatively, the first bonding pads  24  of the data chip  20  may be electrically connected with the wiring  40  by an anisotropic conductive film. 
     Referring to  FIG. 5 , after the data chip  20  is electrically connected to the wiring  40  of the flexible substrate  10 , the control chip  30  is attached onto the second stress absorption member  70  of the flexible substrate  10 . The control chip  30  generates a control signal for inputting/outputting the data stored in the data storage unit  22  of the data chip  20 . The control chip  30  does not include the data storage unit, and therefore the control chip  30  has a relatively small size when compared to a conventional memory semiconductor chip having the data storage unit and the data processing unit together. 
     The control chip  30  includes second bonding pads  34  as shown in  FIG. 2 , and the second bonding pads  34  are electrically connected to the wiring  40  via, for example, a second bump  36 . Alternatively, the second bonding pads  34  of the control chip  30  may be electrically connected to the wiring  40  by an anisotropic conductive film. 
     In the present embodiment, when deflection is generated in the flexible substrate  10 , a shear stress can be applied to the first bump  26  which can in turn cause the first bump  26  to be separated from the first bonding pad  24  or the wiring  40 . In the present embodiment, the wiring  40  can be formed with a recess or a hole for inserting the first bump  26  therein to increase a contact area between the first bump  26  and the wiring  40 . 
     Also, when the deflection is generated in the flexible substrate  10 , a shear stress can be applied to the second bump  36 , which can in turn cause the second bump  36  to be separated from the second bonding pad  34  or the wiring  40 . In the present embodiment, the wiring  40  can be formed with a recess or a hole for inserting the second bump  36  therein to increase a contact area between the second bump  36  and the wiring  40 . 
     Referring again to  FIG. 2 , a flexible protection member  50  is formed over the flexible substrate  10 . The protection member  50  can be a flexible organic layer. The protection member  50  prevents the data chip  20  and the control chip  30  from being damaged by an external impact and/or vibration. 
     As is apparent from the above description, according to the present invention, it is possible to prevent damage of a semiconductor chip when disposing the semiconductor chip over a flexible substrate. 
     Although specific embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and the spirit of the invention as disclosed in the accompanying claims.