Abstract:
A wafer-level package structure, applicable to a flip-chip arrangement on a carrier, which comprises a plurality of contact points, is described. This wafer-level package structure is mainly formed with a chip and a conductive layer. The conductive layer is arranged on the bonding pads of the chip as contact points. The conductive layer can further be arranged at a region outside the bonding pads on the chip as a heat sink to enhance the heat dissipation ability of the package.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the priority benefit of Taiwan application serial no. 91103381, filed on Feb. 26, 2002. 
   BACKGROUND OF INVENTION 
   1. Field of Invention 
   The present invention relates to a wafer-level package structure. More particularly, the present invention relates to a wafer-level package structure that can replace the bump chip carrier (BCC) and the quad flat nonleaded (QFN) type of wafer-level package structure. 
   2. Description of Related Art 
   In today&#39;s information age, the market for multi-media applications is rapidly expanding. The packaging technique for integrated circuits thereby needs to be improved in accordance to the developing trends of electronic devices, such as, digitization, networking, local networking and user friendliness. In order to accommodate the above demands, electronic devices must maintain high operating speed and must be multifunctional, highly integrated, light weight and low cost. Therefore, the packaging technique for integrated circuits must also developed along the direction of further miniaturization and higher integration. Generally speaking, packaging products can be divided into the pin through hole (PTH) type and the surface mount device (SMD). The pin through hole type of packaging basically comprises pins of the device inserting into holes of the circuit board for electrical connection. The pin through hole type of packaging product is the best representative for the dual in-line package (DUP). The surface mount device, however, is directly arranged on a carrier. The contact point of the carrier and the lead of the package are electrically connected through a tin paste. As a result, the package can be easily fixed to the carrier. 
   Referring to  FIGS. 1A and 1B ,  FIGS. 1A and 1B  are schematic diagrams illustrating the cross-sectional views of a conventional bump chip carrier package structure. As shown in  FIG. 1A , a conventional bump chip carrier package structure comprises a chip  100 , a thermal conductive adhesive  104 , a plurality of bonding wires  106 , a plurality of terminals  108  and an encapsulant  110 . The chip  100  comprises a plurality of bonding pads  102 , and the chip  100  is configured on the thermal conductive adhesive  104 . The bonding pads  102  on the chip  100  are electrically connected to the terminals  108  through the bonding wires  106 . The encapsulant  110  is used to encapsulate the chip  100  and the bonding wires  106 . Further, the thermal conductive adhesive  104  is exposed by the encapsulant  110  to enhance thermal dissipation. The terminals  108  are also exposed to the outside of the encapsulant  110  such that the chip  100  can be electrically connected to other carrier. 
   Referring to  FIG. 1B , another type of bump chip carrier package is formed with a chip  100 , a thermal conductive adhesive  104 , a heat sink  114 , a plurality of bonding wires  106  and  112 , a plurality of terminals  108  and an encapsulant  110 . The chip comprises a plurality of bonding pads  102 . Further, the chip  100  is configured on the heat sink  114  with the thermal conductive adhesive  104 . The bonding pads  102  on the chip  100  are electrically connected to the terminals  108  through the bonding wires  106 . The bonding pads  102  are also electrically connected to the heat sink  114  through the bonding wires  112 . The encapsulant  110  is used to encapsulate the chip  100 , the thermal conductive adhesive  104  and the bonding wires  106  &amp;  112 . Further, the heat sink  114  is exposed to the outside of the encapsulant  110  in order for the chip  100  to electrically connected to other carriers through the terminals  108 . 
   Referring to  FIG. 2 ,  FIG. 2  is a schematic diagram illustrating a cross-sectional view of a conventional quad flat nonleaded package structure. The quad flat nonleaded package structure is a leadframe based CSP (Chip Scale Package) constructed on a lead frame. The quad flat nonleaded package is constructed on a lead frame, wherein the lead frame comprises a die pad  214  and a plurality of leads  208 . The chip  200  is configured on the die pad  214  with a thermal conductive adhesive  204 . The chip  200  comprises a plurality of bonding pads  202  thereon, wherein the bonding pads  202  are electrically connected to the leads  208  through the bonding wires  206 . The bonding pads  202  can also be electrically connected to the die pad  214  through the bonding wires  212 . The encapsulant  210  is used to encapsulate the chip  200 , the thermal conductive adhesive  204  and the bonding wires  206 ,  212 . Further, the die pad  214  is exposed to the outside of the encapsulant  210  to enhance the thermal dissipation of the package. The leads  208  are also exposed to the outside of the encapsulant  210  to allow the chip  200  to electrically connected with other carrier. 
   In a conventional BCC, chemical etching must be relied upon to expose the terminals, which greatly complicates the manufacturing process. 
   According to the prior art, wire bonding and molding must be performed regardless the packaging is a BCC type or a QFN type of structure. Therefore, the entire packaging process would become complicated. 
   Further, in the conventional BCC package or the QFN package, both bonding wires and encapsulant would affect the size and the weight of the entire package. 
   SUMMARY OF INVENTION 
   Accordingly, the present invention provides a small-sized, light-weighted and easy manufactured wafer-level package structure. Further, the wafer-level package structure of the present invention is compatible with the BCC package or the QFN package. 
   Accordingly, a wafer-level package structure is provided, which is applicable to a flip-chip arrangement on a carrier with multiple contact points (for example, a printed circuit board). The wafer-level package structure comprises mainly a chip and a conductive layer, wherein the chip comprises a plurality of bonding pads and a protective layer. The protective layer is used to protect the chip surface and to expose the surface of the bonding pad. The conductive layer is configured on the chip. The conductive layer is configured on, for example, the bonding pad, and is used as a contact point for bonding with a carrier. Further, a heat sink is configured at a region outside the bonding pads on the chip to increase the thermal dissipation capability of the package. 
   The chip used in wafer-level package of the present invention is, for example, a chip in which a re-distribution of bonding pads is already accomplished. The chip comprises a wiring and a dielectric layer. The aforementioned dielectric layer is disposed on the protective layer of the chip, wherein the dielectric layer comprises a plurality of openings. The wiring is distributed between the protective layer and the dielectric layer to fan out the bonding pads to appropriate locations, while the openings expose the wiring that is used to fan out the bond pads. 
   In accordance to the wafer-level package, wherein the bonding pads on the chip are, for example, peripherally distributed on the chip, while the heat sink is mounted, for example, inside the region enclosed by the bonding pads. 
   In the wafer-level package of the present invention, the material used to form the bonding pad on the chip includes, for example, copper, aluminum type of material. The material used to form the conductive layer (including the heat sink) includes, for example, aluminum/titanium tungsten alloy/nickel vanadin alloy/copper, chromium/nickel vanadin alloy/copper, aluminum/nickel vanadin alloy/copper and titanium/nickel vanadin alloy/copper type of material. 
   It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, 
       FIGS. 1A to 1B  are schematic diagrams illustrating the cross-sectional views of a conventional bump chip carrier package; 
       FIG. 2  is a schematic diagram illustrating the cross-sectional view of a conventional quad flat nonleaded package; 
       FIG. 3  is a top view of a structure of a wafer-level package without a heat sink according to a first aspect of the present invention; 
       FIG. 4  is a cross-sectional view of the structure in  FIG. 3  along the cutting line I—I; 
       FIG. 5  is a top view of a structure of a wafer-level package with a heat sink according to the first aspect of the present invention; 
       FIG. 6  a cross-sectional view of the structure in  FIG. 5  along the cutting line II—II; 
       FIG. 7  is a top view of a structure of a wafer-level package without a heat sink according to a second aspect of the present invention; 
       FIG. 8  is a cross-sectional view of the structure in  FIG. 7  along the cutting line III—III; 
       FIG. 9  is a top view of a structure of a wafer-level package with a heat sink according to the second aspect of the present invention; and 
       FIG. 10  is a cross-section view of the structure in  FIG. 9 , along the cutting line IV—IV. 
   

   DETAILED DESCRIPTION 
   First Aspect 
   Referring to both  FIG. 3  and  FIG. 4 ,  FIG. 3  is a top view of a structure of a wafer-level package without a heat sink according to the first aspect of the present invention, while  FIG. 4  is a cross-sectional view of the structure in  FIG. 3  along the cutting line I—I. The chip  300  comprises a plurality of bonding pads  302  and a protective layer  304 . The protective layer  304  covers the chip  300  and exposes the bonding pads  302 . The bonding pads  302  are formed with a material such as, copper or aluminum, etc., while the protective layer  304  is formed with, for example, a silicon oxide (SiO x ) material or a silicon nitride (SiN x ) material. 
   The chip  300  further comprises a wiring  306  and a dielectric layer  308  distributed thereon, wherein the dielectric layer  308 , for example, comprises a plurality of openings  310  therein. For example, the openings  310  are distributed peripherally in the dielectric layer  308  on the chip  300 . Moreover, the openings  310  expose the wiring  306  underneath the dielectric layer  308 . The wiring  306  is distributed, for example, above parts of the bonding pads  302  and the protective layer  304 , and uses the bonding pads  302  to fan-out to appropriate locations. The aforementioned dielectric layer  308  includes, for example, polyimide or benzene cyclobutene (BCB), etc., while the circuit line  306  is formed with, for example, copper. 
   Moreover, a conductive layer  312  is configured on the wiring  306  exposed by the opening  310  in the dielectric layer  308 , wherein the conductive layer  312  is used as a contact point for the chip  300  with other carrier. The conductive layer  312  includes, for example, aluminum/titanium tungsten alloy/nickel vanadin alloy/copper, chromium/nickel vanadin alloy/copper, aluminum/nickel vanadin alloy/copper and titanium/nickel vanadin alloy/copper type of material. 
   As shown in  FIG. 3 , since the openings  310  are peripherally distributed in the dielectric layer  308  on the chip  300 , the conductive layer  312  exposed on the surface of the chip  300  is also peripherally distributed. Therefore, for those skilled in the art, it is understood that the opening  310  in the dielectric layer  308  and the conductive layer  312  can be gathered in the center, distributed in a grid array arrangement or other type of arrangement. 
   Referring to both  FIG. 5  and  FIG. 6 ,  FIG. 5  is a top view of a structure of a wafer-level package with a heat sink according to the first aspect of the present invention, while  FIG. 6  is a cross-sectional view of the structure in  FIG. 5  along the cutting line II—II. The difference between the structures in  FIGS. 5 &amp; 6  and in  FIGS. 3 &amp; 4  is the arrangement of a heat sink. 
   According to the structure of the wafer-level package in  FIGS. 5 and 6 , the openings are peripherally distributed in the dielectric layer  308  on the chip  300 . Further, the conductive layer  312  is also peripherally distributed. With the openings  310  and the conductive layer  312  being peripherally distributed, the heat sink  314  above the dielectric layer  308  is configured in the region enclosed by the conductive layer  312  to further increase the heat dissipation capability. 
   Second Aspect 
   Referring to both  FIGS. 7 and 8 ,  FIG. 7  is a top view of a structure of a wafer-level package without a heat sink according to the second aspect of the present invention, while  FIG. 8  is a cross-sectional view of a structure in  FIG. 7  along the cutting line III—III. The chip  300  comprises a plurality of bonding pads  302  and a protective layer  304 . The protective layer  304  covers the chip  300  and exposes the bonding pads  302 , wherein the bonding pads  302  are peripherally distributed on the chip  300 . The bonding pads  302  are, for example, copper or aluminum. The protective layer  304  is formed with, for example, silicon oxide (SiO x ) or silicon nitride (SiN x ) type of material. 
   Further, a conductive layer  312  is configured on the bonding pads  302  exposed on the surface of the chip  300 . This conductive layer  312  is served as a contact point for the chip  300  with other carrier. The conductive layer  312  includes aluminum/titanium tungsten alloy/nickel vanadin alloy/copper, chromium/nickel vanadin alloy/copper, aluminum/nickel vanadin alloy/copper and titanium/nickel vanadin alloy/copper type of material. 
   As shown in  FIG. 8 , the bonding pads  302  are, for example, peripherally distributed on the chip  300 . Therefore, the conductive layer  312  exposed on the surface of the chip  300  is also peripherally distributed. However, for those skilled in the art, it is understood that the bonding pad  302  and the conductive layer  312  can also be distributed in the center, in a grid array arrangement or other type of arrangement. 
   Referring to both  FIG. 9  and  FIG. 10 ,  FIG. 9  is a top view of a structure of a wafer-level package with a heat sink according to the second aspect of the present invention, while  FIG. 10  is a cross-section view of the structure in  FIG. 9 , along the cutting line IV—IV. The wafer-level structure in  FIGS. 9 and 10  is similar to that in  FIGS. 7 and 8 . The only difference is the presence of a heat sink  314 . 
   According to the wafer-level structure shown in  FIGS. 9 &amp; 10 , the bonding pads  302 , for example, are peripherally distributed on the chip  300 , wherein the conductive layer  312  thereabove is also peripherally distributed. Because the bonding pads  302  or the conductive layer  312  is peripherally distributed, the heat sink  314  above the protective layer  304  is arranged inside the region enclosed by the bonding pads  302  and the conductive layer  312  to further enhance the thermal dissipation capability. 
   Accordingly, the wafer-level package structure of the present invention does not require any lead frame. Therefore, the manufacturing process is simpler and more cost effective. 
   Additionally, the wafer-level package structure of the present invention is less heavy compared to the BCC package or the QFN package. 
   In accordance to the wafer-level package structure of the present invention, the bonding pads on the chip are connected to the contact point on the carrier directly with the conductive layer. The signal transmission speed is thereby enhanced. 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.