Abstract:
A package structure having a semiconductor chip embedded therein and a method of fabricating the same are disclosed. The package structure comprises: an aluminum oxide composite plate and a semiconductor chip. The aluminum oxide composite plate is formed by a stack consisting of an adhesive layer placed in between two aluminum oxide layers. The semiconductor chip having an active surface a plurality of electrode pads disposed thereon can be embedded and secured in the aluminum oxide composite plate. The present invention also comprises a method of fabricating the above-mentioned package structure. The present invention provides an excellent package structure, which can decrease the thickness of the package structure and make the package structure having characteristics of high rigidity and enduring tenacity at the same time.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a package structure having a semiconductor chip embedded therein and a method for fabricating the same and, more particularly, to a package structure having characteristics of low thickness, high rigidity and enduring tenacity with a semiconductor chip embedded therein and method for fabricating the same. 
     2. Description of Related Art 
     Customer demands of the electronics industry continue to evolve rapidly and the main trends are high integration and miniaturization. In order to satisfy those requirements, especially in the packaging of semiconductor devices, development of circuit boards with the maximum of active and passive components and conductive wires has progressed from single to multiple layer types. This means that a greater usable area is available due to interlayer connection technology. 
     First, semiconductor chip carriers suitable for semiconductor devices are manufactured through a common semiconductor chip carrier manufacturer. Then, the semiconductor chip carrier is processed by semiconductor chip attachment, wire bonding, molding, and implanting solder ball etc. for assembling semiconductor devices. Finally, the semiconductor devices having electronic functions required by clients are completed. Because the steps of the practical manufacture are minute and complex, interfaces are not integrated easily at the time when manufactured by different fabricating proprietors. Further, if the client wants to change the design of the function, efficiency and economic benefit suffer. 
     In the conventional semiconductor device structure, semiconductor chips are mounted on top of a substrate, and then processed in wire bonding, or connected the chip which having the solder bump thereon to the conductive pads on the substrate, followed by placing solder balls on the back of the substrate to provide electrical connections for printed circuit board. Although an objective of high quantity pin counts is achieved, this condition is limited by way of long pathways of conductive lines making electric characteristics unable to be improved in the more frequent and high-speed operating situations. Otherwise, the complexity of the manufacture is relatively increased because too many connective interfaces are required for conventional packages. 
     In many studies, semiconductor chips directly conducting to external electronic devices are embedded into a package substrate to shorten conductive pathways, decrease signal loss and distortion, and increase abilities of high-speed operation. 
     In a carrier having a semiconductor chip embedded therein, for preventing destruction of the chip in carrier by laser drilling, as shown in  FIG. 1 , metal layers are added on electrode pads of an active surface of the semiconductor chip. The structure of the carrier having a semiconductor chip embedded therein includes: a carrier  11 , in which a cavity is formed; a semiconductor chip  12  which is set in the cavity, and a plurality of electrode pads  13  formed on an active surface of the semiconductor chip  12 ; a protective layer  14  formed on the carrier  11  having the semiconductor chip  12  embedded therein, and then the a plurality of electrode pads  13  are exposed; a plurality of metal layer  15  formed on surfaces of the electrode pads  13 ; and a build-up structure  16  formed on surfaces of the semiconductor chip  12  and the carrier  11 . The build-up structure  16  is formed on the surfaces of the semiconductor chip  12  and the carrier  11 , and conducts the electrode pads  13  of the semiconductor chip  12  . 
     Currently, in a package structure having the semiconductor chip embedded therein, stress between the build-up structure and the non-build-up structures is not the same. Because the build-up structure is asymmetric, the metal carrier becomes warp. Under this condition, production becomes complex, and excessively warped carriers cause low yield and low stability of products. 
     Therefore, in order to prevent semiconductor chip-embedded carriers becoming warp due to an asymmetric build-up structure and to improve the yield of the process, carriers made of copper or bismaleimide-triazine (BT) resin already have not satisfy needs of the utilization. 
     SUMMARY OF THE INVENTION 
     In view of the above conventional shortcomings, the present invention provides a package structure having a semiconductor chip embedded therein, and comprising an aluminum oxide composite plate and at least one build-up structure. The aluminum oxide composite plate is composed of an adhesive layer placing between two aluminum oxide plates, and a cavity extending through the upper and lower surface of the aluminum oxide composite plate. The semiconductor chip is embedded and secured in the cavity of the aluminum oxide composite plate and has an active surface with a plurality of electrode pads set thereon. The build-up structure placed on a surface of the aluminum oxide composite plate being the same lateral side as the active surface of the semiconductor chip. The build-up structure comprises a dielectric layer, a plurality of circuit layers on the dielectric layer, and forming a plurality of conductive structures in the dielectric layer to conduct the electrode pads of the semiconductor chip to outside electronic devices. 
     In the package structure of the present invention, in order to secure the semiconductor chip inside the aluminum oxide composite plate, gaps between the semiconductor chip and the cavity in the aluminum oxide composite plate are filled either with epoxy resin. Or through laminating a dielectric layer on a surface of the aluminum oxide composite plate being the same lateral side as the active surface of the semiconductor chip, part of the dielectric layer fills into gaps between the semiconductor chip and the cavity in the aluminum oxide composite plate in order to secure the semiconductor chip inside the aluminum oxide composite plate. 
     In the package structure of the present invention, material of the dielectric layer laminated on the surface of the aluminum oxide composite plate being the same lateral side as the active surface of the semiconductor chip, is any one selected from a group consisting of Ajinomoto Build-up Film™ (ABF), bismaleimide triazine (BT), benzocyclobutene (BCB), liquid crystal polymer, polyimide (PI), poly(phenylene ether), poly(tetra-fluoroethylene), aramide, epoxy resin, and fiber glass. Preferably, the dielectric layer is composed of ABF. 
     In the package structure of the present invention, the conductive structure of the build-up structure is conductive via, and the circuit layers and conductive structures of build-up structure can be made of copper, tin, nickel, chromium, palladium, titanium, tin/lead, or alloy thereof. Preferably, the circuit layers and conductive structures can be made of copper. Besides, a plurality of conductive pads are set on a surface of the build-up structure. Further, a patterned solder mask layer is set on the surface of the build-up structure, and to expose the most outer circuit layer for setting the conductive pads. On the conductive pads, solder bumps are set, and can be made of any one of the group consisting of copper, tin, lead, silver, nickel, gold, platinum, or alloy thereof. Preferably, the solder bumps are composed of tin. 
     In the package structure of the present invention, the adhesive layer placing between two aluminum oxide plates can be made of any material able to adhere the two aluminum oxide layers, which is neither softened nor decomposed under heating. Preferably, the adhesive layer can be composed of thermosetting resin, e.g. epoxy resin or phenolic-aldehyde resin. 
     In the package structure of the present invention, the electrode pads on the active surface of the semiconductor chip have a function of conducting the semiconductor chip to outside electronic devices, and then the semiconductor chip can function. Therefore, the electrode pads can be made of any material which has an electrically conductive characteristic, but preferably is composed of copper or aluminum. 
     According to the above-mentioned package structure having a semiconductor chip embedded therein in the present invention, a method for fabricating the same can comprise the following steps, but is not limited thereto. 
     Therefore, the present invention further provides a method for fabricating a package structure having a semiconductor chip embedded therein comprising the following steps: first, providing two aluminum plates; second, oxidizing one surface of each aluminum plate and then the two aluminum plates both having an aluminum oxide layer and an aluminum layer; then arranging the aluminum oxide layers of the two aluminum plate to face to each other, and an adhesive layer being placed between the two aluminum plate; subsequently removing the aluminum layers of the two aluminum plates, and forming an aluminum oxide composite plate; forming a cavity in the aluminum oxide composite plate extending through upper and lower surface of the aluminum oxide composite plate, and embedding a semiconductor chip secured into the cavity, wherein a plurality of electrode pads are disposed on an active surface of the semiconductor chip, and finally, forming at least one build-up structure placed on a surface of the aluminum oxide composite plate being the same lateral side as the active surface of the semiconductor chip, wherein the build-up structure comprises a dielectric layer, a plurality of circuit layers on the dielectric layer, and forming a plurality of conductive structures in the dielectric layer to conduct the electrode pads of the semiconductor chip to outside electronic devices. 
     In the method of the present invention, the semiconductor chip is secured either by way of dropping or pouring glue, or through laminating a dielectric layer into gaps between the semiconductor chip and the cavity to secure the semiconductor chip. 
     The method in the present invention comprises a step of forming abuild-up structure placed on a surface of the aluminum oxide composite plate being the same lateral side as the active surface of the semiconductor chip. The build-up structure can exceed one if it is necessary. The build-up structure has a plurality of conductive structures, and conductive structures can conduct the electrode pads of the semiconductor chip to outside electronic devices, or conduct one circuit layer to another in the build-up structure. Generally, the conductive structures are conductive vias. 
     The method in the present invention further comprises a step of forming a patterned solder mask layer on the outside surface of the build-up structure. On the patterned solder mask layer, a plurality of openings are formed to expose the circuit layers for setting the electrically conductive pads thereon. 
     The method in the present invention further comprises a step of forming a plurality of solder bumps on the electrically conductive pads of the build-up structure through electroplating or printing. 
     In the method of the present invention, the aluminum oxide layers are formed on one lateral of the aluminum plates through any method, but preferably by anodic oxidation. 
     In the method of the present invention, the aluminum layers of the two aluminum plates can be removed by etching. 
     Before embedding the semiconductor chip in the cavity of the aluminum oxide composite plate in the present invention, a release film is adhered on a surface of the aluminum oxide composite plate being the same lateral side as a non-active surface of the semiconductor chip and removed after the semiconductor chip is secured. After the semiconductor chip is secured onto the aluminum oxide composite plate, the release film is removed. Material of the release film is not limited, but preferably is any material of temporarily securing the semiconductor chip. 
     Therefore, the package structure having the semiconductor chip embedded therein and the method for fabricating the same in the present invention solves the problem of the plate warp causing by unequal stress of asymmetric build-up structures. The composite plate of the package structure has a characteristic of high rigidity, and can restrain the unequal stress of the asymmetric build-up structures so as to prevent occurrence of the plate warp. The surface of the aluminum plate is oxidized to form an aluminum oxide layer (ceramics) thereon through oxidation, e.g. anodic oxidation, and an adhesive layer is adhered tightly between the two aluminum oxide layers. Forming the aluminum oxide composite plate of the present invention needs no other additional step, e.g. no sintering is required. The technology and fabrication of the aluminum oxide composite plate of the present invention are simple, and thus mass production is particularly enabled. 
     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a conventional carrier having a semiconductor chip embedded therein; 
         FIGS. 2A to 2G  are cross-sectional views showing the embodiment of a method for fabricating a package structure having a chip embedded therein of the present invention; 
       FIGS.  2 F′ to  2 G′ are cross-sectional views showing the embodiment of a method for fabricating a package structure having a chip embedded therein of adding a build-up structure and solder bumps of a package structure; and 
         FIG. 3  is a perspective view of an aluminum oxide composite plate having a semiconductor chip secured therein in another preferable embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Because of the specific embodiments illustrating the practice of the present invention, a person having ordinary skill in the art can easily understand other advantages and efficiency of the present invention through the content disclosed therein. The present invention can also be practiced or applied by other variant embodiments. Many other possible modifications and variations of any detail in the present specification based on different outlooks and applications can be made without departing from the spirit of the invention. 
     The drawings of the embodiments in the present invention are all simplified charts or views, and only reveal elements relative to the present invention. The elements revealed in the drawings are not necessarily aspects of the practice, and quantity and shape thereof are optionally designed. Further, the design aspect of the elements can be more complex. 
     Embodiment 1 
     With reference to  FIGS. 2A to 2E , there is shown a perspective view of fabricating a package structure having a semiconductor chip embedded therein in the present invention. 
     As shown in  FIG. 2A , two aluminum plates  21  are provided first. The two aluminum plates  21  are put into an electrolytic tank to proceed with anodic oxidation. Therefore, one surface of the aluminum plate  21  is oxidized to form an aluminum oxide layer  21   a , and the other surface of the aluminum plate  21  remains as an aluminum layer  21   b . In the present embodiment, the thickness of the aluminum oxide layer  21   a  is controlled by duration of anodic oxidation. Subsequently, as shown in  FIG. 2B , the aluminum oxide layers  21   a  of the two aluminum plates  21  face each other, and an adhesive layer  22  is tightly placed therebetween. The material of the adhesive layer  22  can be thermosetting resin, and in the present embodiment, the adhesive layer  22  is made of epoxy resin. Then, the respective aluminum layers  21   b  of the two aluminum plates  21  are removed by etching, and an aluminum oxide composite plate  20  is obtained, as shown in  FIG. 2C . The structure of the aluminum oxide composite plate  20  is a sandwich structure of the two aluminum oxide layers  21   b  and the adhesive layer  22 . 
     As shown in  FIG. 2D , a cavity  23  is formed in the aluminum oxide composite plate  20  generally through chemical etching, and the cavity  23  extending through the upper and lower surface of the aluminum oxide composite plate  20 . A semiconductor chip  24 , which is cut and formed by wafer integrated circuit processes, is embedded in the cavity  23  of the aluminum oxide composite plate  20 . The semiconductor chip  24  has an active surface  24   a . A plurality of electrode pads  24   b  are disposed on the active surface  24   a  of the semiconductor chip  24 , and is made of copper. At the same time, a release film or an adhesive tape (not shown in figures) is adhered on a surface of the aluminum oxide composite plate  20  being the same lateral side as a non-active surface  24   c  of the semiconductor chip  24 , and then the semiconductor chip is embedded in the cavity  23 . 
     Subsequently, as shown in  FIG. 2E , dropping adhesive material  25   a  thereinto fills gaps between the cavity  23  and the chip  24 , and the semiconductor chip  24  is thus secured in the cavity  23  of the aluminum oxide composite plate  20 . The adhesive material  25   a  can be epoxy resin. Then, the release film (not shown in figures) on the surface of the aluminum oxide composite plate  20  is removed. Finally, the package structure having the semiconductor chip embedded therein in the present invention is obtained. 
     With reference to  FIG. 2F  and FIG.  2 F′, a dielectric layer  26  is laminated on another surface of the aluminum oxide composite plate  20  being the same lateral side as the active surface  24   a  of the semiconductor chip  24 . On the dielectric layer  26 , a plurality of circuit layers  27  and conductive structures  28   a  (shown in  FIG. 2F ) or conductive structures  28   b  (shown in FIG.  2 F′) are formed to be a build-up structure  30   a  (shown in  FIG. 2F ) or a build-up structure  30   b  (shown in FIG.  2 F′). At the same time, the electrode pads  24   b  of the semiconductor chip  24  are conducted to the circuit layers  27  by the conductive structures  28   a  (shown in  FIG. 2F ) or the conductive structures  28   b  (shown in FIG.  2 F′). In the present embodiment, the non-active surface  24   c  is exposed advantageously for cooling the semiconductor chip  24 . 
     As shown in  FIG. 2G , other build-up structures  31   a  are formed on the dielectric layer  26  through build-up technology if it is necessary. A patterned solder mask layer  33  is formed on an outside surface of the build-up structures  31   a , and the circuit layers for disposing electrically conductive pads  32  are exposed through the patterned solder mask layer  33 . Material of the patterned solder mask layer  33  can be photo-image insulating material. Finally, solder bumps  34  corresponding to the electrically conductive pads  32  are formed by electroplating or printing. Material of the solder bumps  34  can be any one of the group consisting of copper, tin, lead, silver, nickel, gold, platinum, and alloy thereof. 
     Therefore, the package structure having the semiconductor chip embedded therein in the present invention, as shown in  FIGS. 2F and 2G , includes the aluminum oxide composite plate  20  and the semiconductor chip  24 . The aluminum oxide composite plate  20  is composed of the adhesive layer  22  placed between the two aluminum oxide layers  21   a . The semiconductor chip  24  is embedded and secured in the cavity  23  of the aluminum oxide composite plate  20 , and has the active surface  24   a  on which the a plurality of electrode pads  24   b  are disposed. At least one build-up structure  30   a  is formed on a surface of the aluminum oxide composite plate  20  being the same lateral side as the active surface  24   a  of the semiconductor chip  24 , the build-up structure  30   a  comprises a dielectric layer  26 , a plurality of circuit layers  27  on the dielectric layer  26 , and forming a plurality of conductive structures  28   a  in the dielectric layer  26  to conduct the circuit layers  27 . 
     As shown in FIG.  2 G′, a package structure having the semiconductor chip  24  embedded in the aluminum oxide composite plate  20  with another build-up structure  31   b  can also be obtained. 
     Therefore, the package structure having the semiconductor chip embedded therein in the present invention, as shown in  FIG. 2E , includes the aluminum oxide composite plate  20  and the semiconductor chip  24 . The aluminum oxide composite plate  20  is composed of the adhesive layer  22  placed between the two aluminum oxide layers  21   a , and forming a cavity  23  in the aluminum oxide composite plate  20  extending through upper and lower surface of the aluminum oxide composite plate. The semiconductor chip  24  is embedded and secured in the cavity  23  of the aluminum oxide composite plate  20 , and has the active surface  24   a  on which the a plurality of electrode pads  24   b  is disposed. 
     Embodiment 2 
     The method for fabricating a package structure having a semiconductor chip embedded therein in the present embodiment is very similar to Embodiment 1. Except for a step of securing a semiconductor chip  24  into an aluminum oxide composite plate being different from Embodiment 1, all other aspects are approximately the same as those of Embodiment 1. 
     As shown in  FIG. 3 , the semiconductor chip  24  is secured in an aluminum oxide composite plate  20 . When the semiconductor chip  24  is embedded in the aluminum oxide composite plate  20 , epoxy resin is not utilized, but a dielectric layer  26  (e.g. ABF) is laminated into gaps between the semiconductor chip  24  and a cavity  23  of the aluminum oxide composite plate  20 . The dielectric layer  26  functions as the adhesive material. Other steps are similar to the steps of Embodiment 1. Finally, the package structure having the semiconductor chip embedded therein is obtained. 
     Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed.