Abstract:
Electronic packages incorporating EMI shielding, and particularly semiconductor devices which incorporate semiconductor chip-carrier structures having grounded bands embedded therein which are adapted to reduce outgoing and incident EMI emissions for high-speed switching electronic packages.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electronic packages incorporating EMI shielding. More particularly, the invention relates to semiconductor devices which incorporate integrated circuit chip-carrier structures having grounded shields embedded therein and which are adapted to reduce EMI emissions for high-speed switching electronic packages. 
     In carrying out the production of electronic packages, particularly such as semiconductor devices which incorporate chip carriers or substrates of either laminates or organic materials or ceramics and the like, and which support one or more semiconductor chips which are covered by a heat-dissipating lid or cap structure, the reliable functioning thereof is potentially adversely affected due to encountered electromagnetic interference (EMI), requiring that an EMI shield be provided to counteract and eliminate the adverse effects thereof. Moreover, the EMI shielding is intended to also function as an emission shield; in effect, to inhibit or stop outgoing EMI energy. Quite frequently, such semiconductor devices may comprise a substrate providing for electrical connections to one or more semiconductor chips positioned thereon, and whereby a heat-dissipating structure; for instance, such as a heat spreader in the form of a cap or lid is, in turn, arranged above the chip or chips and in thermally-conductive mechanical adhesive connection therewith. 
     Various electrical components and interconnects are normally provided on both sides of the substrates in electrical communication with the chip or chips, as is well known in the semiconductor or electronic packaging technology. In order to effectively screen out any encountered EMI during operation of the semiconductor devices, it has been proposed to provide structure extending about the chip and interposed between the heat-dissipating lid structure or cap, and also the substrate, in that suitable connections or wiring is to be provided, thereby creating an EMI shield for the semiconductor device or electronic package. In this connection, numerous types of EMI shields or similar types of EMI protective structures for the electronic packages or semiconductor devices have been proposed in the technology, possessing varying degrees of efficacy in protecting or shielding the devices from electromagnetic interference (EMI). 
     2. Discussion of the Prior Art 
     Accordingly, among numerous publications in this particular field of the technology which is directed to the provision of EMI shielding for electronic packages, such as semiconductor devices, Mertol U.S. Pat. No. 5,866,943 discloses a system and method for forming a grid array device package employing electromagnetic shielding, in which a stiffener is disposed intermediate a substrate and a lid or cap structure having a semiconductor chip interposed therebetween. The stiffener which encompasses the semiconductor chip includes various electrical interconnections between the semiconductor chip, substrate and the heat spreader or cover so as to, in effect, provide for the necessary EMI shield to protect against the effects of EMI during operation of the electronic package. 
     Mostafazadeh et at. U.S. Pat. No. 5,650,659 discloses a semiconductor component package assembly, which includes an EMI shield interposed between a substrate and a heat dissipating structure, and encompassing an integrated circuit chip to provide for electrical connections forming an integral radio frequencies/electromechanical interference (RF/EMI) shield. In one particular embodiment, an adhesive of an electrically conductive nature may be interposed between the substrate and the structure forming the EMI shield as necessary to provide for the electrical grounding of the component. 
     King et al. U.S. Pat. No. 5,761,053 also discloses a Faraday cage in which a cover positioned on a substrate and encompassing integrated circuit components enables the energy of EMI/RFI to be dissipated so as to render the effects thereof harmless to the operation of the device. 
     Similarly, Osorio U.S. Pat. No. 5,317,107 discloses a semiconductor device including a substrate and a cover portion having an integrated circuit chip interposed therebetween, and including shielding to block EMI energy which would have an adverse effect on the functioning of the device. 
     In addition to the foregoing publications, numerous other patents are in existence which are directed to providing EMI shielding to various electronic structures of the most diverse types. 
     Hutchison et al. U.S. Pat. No. 6,261,251 discloses a wirebond package for low cost (radio frequency) applications utilizing a complex metal-lead frame structure to provide for isolation from disruptive frequencies. 
     Glenn U.S. Pat. No. 5,939,784 discloses a package for a wirebond die employed in a acoustical wave device, and which possess an EMI shielded surface. 
     Hurst et al. U.S. Pat. No. 5,939,772 discloses a wirebond package incorporating metal plates in a surrounding configuration which are adapted to impart magnetic shielding to the package. 
     Sakai et al. U.S. Pat. No. 5,838,093 discloses a piezoelectric element package incorporating a device with a surrounding metal cup which provides shielding from EMI energy during functioning of the package. 
     Miyawaki et al. U.S. Pat. No. 5,536,907 discloses a wirebond package for a semiconductor device including a metal lid incorporated therein and structure providing for EMI shielding. 
     Benavides et al. U.S. Pat. No. 5,254,871 provides for a tape automatic bonding (TAB) carrier including an incorporated or integrated heatsink and metal plate construction which enables functioning thereof as an EMI shielding. Jones U.S. Pat. No. 5,227,583 discloses a wirebond package having a ceramic lid which is metallized as a signal shielding component protective from the energy generated by EMI. 
     Furthermore, Schelhorn U.S. Pat. No. 4,967,315; Kling U.S. Pat. No. 4,323,155; Hayashi U.S. Pat. No. 5,898,344; Strobel et al. U.S. Pat. No. 5,635,754; Marrs U.S. Pat. No. 5,485,037; Bethurum U.S. Pat. No. 5,477,421; Moulton, et al. U.S. Pat. No. 5,371,408; Knecht, et al. U.S. Pat. No. 5,313,371; and Mahulikar et al. U.S. Pat. No. 5,043,534 each, to some extent, describe various types of structures in the shape of either electronic packages or semiconductor devices which incorporate EMI shielding arrangements so as to inhibit the effects of EMI on the performance of the various devices or electronic packages. 
     Although the foregoing publications are each to varying degrees directed to the incorporation of EMI shielding, the present invention is concerned with the advantageous configurations of grounded-lid or electronic packages which are particularly suitably adapted for extremely high-speed electronic switching applications, such as for Hyper BGAs&#39;, (reg. ™) and which require a highly efficient type of EMI shielding. 
     SUMMARY OF THE INVENTION 
     Accordingly, pursuant to one embodiment of the invention there is provided a semiconductor device comprising an organic substrate or chip carrier, wherein a lid of a electrically and thermally-conductive structure is attached to a stiffener which is interposed between the perimetrical regions of the substrate and the lid, and wherein an integrated circuit or semiconductor chip is positioned between the lid and the organic substrate, while encompassing the stiffener, and includes an adhesive between the chip and substrate which is of a compliant, thermally conductive nature so as to promote a good thermo-mechanical connection of good reliability between the components. Arranged embedded in the organic carrier is an electrically conductive ground band so as to extend around the perimeter portion of the carrier and between the top and bottom surfaces of the substrate. The stiffener may be attached to the substrate by means of an electrically non-conductive adhesive material so as to cover the active circuitized area on the chip carrier or substrate extending about the integrated circuit chip, and with an electrically-conductive adhesive material extending over the ground band which is embedded in the substrate. 
     Pursuant to a second embodiment of the invention, the chip carrier or substrate may comprise a rigid ceramic element mounting a ball grid array (BGA), which element interconnected to a chip through the intermediary of solder balls which may be embedded in an underfill. An electrically and thermally-conductive lid, such as a heat-dissipating cap structure is superimposed on the chip and is connected thereto by means of a suitable dielectric adhesive. A conductive ground band is formed proximate the perimeter in the ceramic substrate so as to be embedded therein, and with an EMI gasket of electrically conductive nature interconnecting the ground with the heat-dissipating lid or cap structure. The ground ring component forms a grounded connection with the ball grid array to produce an EMI shield for the entire arrangement. 
     Pursuant to a third embodiment of the invention, which is generally similar to the second embodiment as mentioned hereinabove, the lid or cap structure may have a depending annular flange portion which electrically communicates with the embedded wiring forming the ground band in the perimeter area of the ceramic substrate by means of an EMI adhesive, whereas in the preceding embodiment, rather than an adhesive there is employed an EMI gasket. 
     The rigid or inherently stiff nature of the substrates utilized in the second and third embodiments, such as the ceramic chip carrier, eliminates the need for the provision of a stiffener structure as is required in connection with the less rigid organic substrate or laminated chip carrier of the first embodiment. 
     Accordingly, it is an object of the present invention to provide a novel electronic package arrangement incorporating EMI shielding comprising a stiffener positioned intermediate a substrate of an organic nature and an electrically conductive lid or heat dissipating cap between which there is arranged an integrated circuit chip encompassed by the stiffener, and wherein the substrate is provided with ground connections for producing an EMI shield, with a ground ring being embedded in the perimetrical region of the organic substrate. 
     A further object of the present invention resides in the provision of an electronic package of the type described comprising an EMI barrier to incident or incoming EMI energy. 
     A still further object of the present invention resides in the provision of an electronic package of the type described herein comprising an EMI shield for outgoing or emitted EMI energy. 
     Pursuant to a further object of the present invention there is provided an arrangement which imparts EMI shielding to a semiconductor package the type of described wherein an EMI gasket is interposed between a ceramic substrate having band-shaped grounding wires imbedded proximate the perimeter thereof, and providing for electrical interconnections with a metallic lid or heat-dissipating cap structure and with a ball grid array on the substrate. 
     Yet another object of the present invention is to provide an electronic package or semiconductor structure which includes an EMI adhesive interposed between an annular depending flange on a heat-dissipating lid or cap, and electrically conductive wiring embedded in a ceramic substrate and connected to a ball grid array so as to form a grounding connection with the metallic lid, so as to produce an EMI shield for the structure. 
     Moreover, another object of the invention resides in a method of utilizing the EMI shielding as installed in an electronic package as described herein. 
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     Reference may now be made to the following detailed description of preferred embodiments of electronic packages or semiconductor devices equipped with EMI shielding, taken in conjunction with the accompanying drawings; in which: 
     FIG. 1 illustrates generally diagrammatically, a first embodiment in a partial cross-sectional representation of a semiconductor package, including an organic substrate and a stiffener structure employed in forming a grounded EMI shield; 
     FIG. 2 illustrates a second embodiment of a package with a ceramic substrate including an embedded ground ring electrically communicating with a lid through an EMI gasket to form an EMI shield in a semiconductor package; and 
     FIG. 3 illustrates a third embodiment of a semiconductor package similar to the second embodiment but utilizing an EMI adhesive rather than a gasket interposed between electrical ground wires extending perimetrically within a ceramic substrate and a conductive cap or lid. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring in more specific detail to the drawings, and particularly to the embodiment as illustrated in FIG. 1, there is diagrammatically represented a semiconductor package  10  comprising an organic substrate  12 , which may be constituted of a laminate, and wherein an integrated circuit chip  14  is shown positioned thereon. Interposed between the chip  14  and the substrate  12  are suitable solder balls  16 , as is well known in the technology, and which may be encapsulated in an underfill material  17 . 
     Arranged above the chip  14 , opposite the side facing the substrate  12 , and extending radially outwardly of the chip  14  is a lid or heat-dissipating cap structure  18  of an electrically-conductive material, for instance, such as but not limited to copper, aluminum, tin, chromium, silicon, carbide, carbon, diamond, ceramic with electrically-conductive coatings, alloys and compositions thereof, and the like, as are well known in the technology, which is attached to the chip by means of a thermally-conductive compliant adhesive  20  in order to promote good thermo-mechanical reliability in their interconnection, the adhesive being essentially of an electrically non-conductive or low-conductive nature in composition, such as being a silver-filled adhesive which is both thermally and electrically-conductive. 
     Positioned to extend along a peripheral region  22  intermediate the lower surface of the lid or cap structure  18  and the upper surface of the organic substrate  12  is a stiffener member  24  which, in its plane, may be essentially of a box-shaped configuration with a central opening  26  extending in spaced relationship about the peripheral extent of the chip  14 . The stiffener member  24  may be of a suitable electrically-conductive material, similar to the lid or heat-dissipating cap  18 , by being constituted of the materials as set forth hereinabove, of both metallic and non-metallic compositions. The lid or cap structure  18  is fastened to the stiffener  24  through the interposition of an electrically-conductive adhesive  28 , whereas in contrast, the adhesive between the chip and lid is normally a compliant thermally conductive and electrically non-conductive adhesive. Alternatively, the adhesive  28  may be electrically non-conductive but provided with internal conductive elements to form an electrical path between the stiffener  24 , lid  18  and the substrate  12 . 
     As indicated, pursuant to invention, the opposite side of the organic substrate  12  may include electrical connections to the solder balls  16 , such as for example, such as a circuit path to array a BGA  30 , only schematically indicated, and which form electrical interconnections with the chip  14 , as is well known in the technology. 
     The area along the perimeter of the organic substrate  12  includes embedded therein a ring-shaped electrical ground band  32  extending between the top surface of the organic substrate and the connections  30  at the opposite surface thereof. The attachment of the stiffener  24  to the lid or cap  18 , as indicated previously, is an electrically conductive adhesive material, and on the opposite side of the stiffener facing the substrate, an electrically-nonconductive adhesive  34 , such as pyrolux, which covers the active circuitized area on the substrate, and a further electrically conductive adhesive material  36  extending over the ground band  32  on the upper surface of the organic substrate  12  so as to form an electrical connection with the stiffener  24 , whereas the ground band at the lower surface of the substrate electrically contacts the ball grid array  30 . The internal electrical circuitization on the substrate upper surface has a connection  38  formed with the ground band  32  and one or more solder balls  16  on the perimeter of the module, thereby resultingly creating an electromagnetic interference (EMI) shield for the entire semiconductor package  10 , shield against outgoing EMI energy and also forming a barrier to incoming or incident EMI energy. 
     Although, in essence the basic concept of providing EMI shields for various types of devices is known in the technology, it is the specific and advantageous arrangement of the ground ring  32  embedded within the organic substrate  12  in communication with the stiffener  24 , which in this embodiment creates a superior and unique EMI shield which is particularly effective for the very high speed switching applications of semiconductor devices which are currently being contemplated in the technology. 
     Referring now to the embodiment of FIG. 2 of the drawings, in this instance, the stiffener utilized in the embodiment of FIG. 1 has been eliminated, inasmuch as herein a substrate  40  is comprised of a rigid ceramic material, and consequently does not necessitate the use of a stiffener member; the stiffness being inherently provided by the properties of ceramic material. 
     As in the previous embodiment, an integrated circuit chip  42  is arranged on an upper surface of the ceramic substrate  40 , with the interposition of solder balls  44  which are embedded in an underfill material  46 . A lid or heat-dissipating cap structure  48  which extends radially outwardly of the peripheral confines of the integrated circuit chip  42 , and which is constituted of an electrically-conductive material, such as has been described in connection with lid or cap structure is, in electrical communication with a ground band  50  consisting of wires embedded within the peripheral region of the substrate  40  and extending between the opposite surfaces thereof. An EMI gasket  52  presenting an electrically-conductive path is interposed between the lid  48  and the upper wire ends of the ground band  50 , the latter of which is embedded within the substrate and is located along the perimeter of the latter, whereby the gasket  52  may be adhered to either the lid or the ground band. The lower end of the ground band  50  is in electrically grounding connection with a ball grid array  56  on the surface of the substrate distal to the chip, and further electrical connections can be provided with the chip through one or more of the solder balls and the adhesive extending between the lid and the ground band wire ends at the upper surface of the substrate  40 . 
     With regard to the embodiment of FIG. 3 of the drawings, which is substantially similar to that of FIG. 2, in this instance, the electrically-conductive cap or lid structure  48  is equipped with a depending peripheral flange  60  having a lower end surface  62  in close proximity with the upper surface of the ceramic substrate  40 . Hereby, in lieu of the gasket  52  of adhesive material of FIG. 2 extending between the lower surface of the lid and the upper wire ends of the peripherally embedded ground band  50 , there is utilized an electrically conductive EMI adhesive  64  which also communicates with at least one of the solder balls  44  and integrated circuit on the chip so as to form an EMI shield structure similar to that in the embodiments of FIGS. 1 and 2. 
     The foregoing constructions including the novel ground bands which are embedded in the perimetrical region of the substrates  12 , 40  of the various embodiments, provide a highly effective EMI shield or barrier surrounding the entire package or semiconductor structure, thereby reducing or even completely eliminating any outgoing EMI emissions and incoming EMI energy encountered during the operation of the modules. While the invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.