METHODS AND APPARATUS FOR PRODUCING INTEGRATED CIRCUIT DEVICES

Abstract: A method for producing integrated circuit devices including the steps of producing a plurality of integrated circuits on a wafer having first and second planar surfaces, each of the integrated circuits including a multiplicity of pads, waferwise attaching to both said surfaces of the wafer a layer of protective material, thereafter partially cutting into the wafer and the protective material attached thereto, thereby to define notches along outlines of a plurality of prepackaged integrated circuit devices, forming metal contacts onto the plurality of prepackaged integrated circuit devices while they are still joined together on the wafer, at least a portion of said metal contacts extending into the notches and thereafter separating the plurality of prepackaged integrated circuit devices into individual devices. Integrated circuits produced according to the method are also disclosed and claimed.

Description: METHODS AND APPARATUS FOR PRODUCING INTEGRATED CIRCUIT DEVICES FIELD OF THE INVENTION The present invention relates to methods and apparatus for producing integrated circuit devices and to integrated circuit devices produced thereby. BACKGROUND OF THE INVENTION An essential step in the manufacture of all integrated circuit devices is known as "packaging" and involves mechanical and environmental protection of a silicon chip which is at the heart of the integrated circuit as well as electrical interconnection between predetermined locations on the silicon chip and external electrical terminals. At present three principal technologies are employed for packaging semiconductors: wire bonding, tape automatic bonding (TAB) and flip chip. Wire bonding employs heat and ultrasonic energy to weld gold bonding wires between bond pads on the chip and contacts on the package. Tape automatic bonding (TAB) employs a copper foil tape instead of bonding wire. The copper foil tape is configured for each specific die and package combina¬ tion and includes a pattern of copper traces suited thereto. The individual leads may be connected individu¬ ally or as a group to the various bond pads on the chip. Flip chips are integrated circuit dies which have solder bumps formed on top of the bonding pads, thus allowing the die to be "flipped" circuit side down and directly soldered to a substrate. Wire bonds are not required and considerable savings in package spacing may be realized. The above-described technologies each have certain limitations. Both wire bonding and TAB bonding are prone to bad bond formation and subject the die to relatively high temperatures and mechanical pressures. Both wire bond and TAB technologies are problematic from a package size viewpoint, producing integrated circuit devices having a die-to-package area ratio ranging from about 10% to 60%. The flip-chip does not provide packaging but rather only interconnection. The interconnection encoun¬ ters problems of uniformity in the solder bumps as well as in thermal expansion mismatching, which limits the use of available substrates to silicon or materials which have thermal expansion characteristics similar to those of silicon. SUMMARY OF THE INVENTION The present invention seeks to provide appara¬ tus and techniques for production of integrated circuit device overcome many of the above limitations and provide integrated circuits of relatively smaller size and weight and enhanced electrical performance. There is thus provided in accordance with a preferred embodiment of the present invention a method for producing integrated circuit devices including the steps of; producing a plurality of integrated circuits on a wafer having first and second planar surfaces, each of the integrated circuits including a multiplicity of pads; waferwise attaching to both said surfaces of the wafer a layer of protective material; thereafter partially cutting into the wafer and the protective material attached thereto, thereby to define notches along outlines of a plurality of prepack¬ aged integrated circuit devices; forming metal contacts onto the plurality of prepackaged integrated circuit devices while they are still joined together on the wafer, at least a portion of said metal contacts extending into the notches; and thereafter separating the plurality of prepack¬ aged integrated circuit devices into individual devices. Throughout the specification and claims, the terms "cutting" and "cut" shall have broader than usual meaning and shall refer to removal of material or sepa¬ rating along a line by any suitable technique, such as, for example, etching, sawing, sandblasting and milling. It is noted that the term "waferwise" does not require that a whole wafer be so processed at a given time. "Waferwise" applies equally to steps applied to multiple dies prior to dicing thereof. In accordance with a preferred embodiment of the present invention the step of partially cutting exposes sectional surfaces of the multiplicity of pads. Preferably the step of partially cutting cuts pads so as to simultaneously define electrical contact regions for both of a pair of adjacent integrated cir¬ cuits. Additionally in accordance with a preferred embodiment of the present invention there is provided a method for producing integrated circuit devices including the steps of: producing a plurality of integrated circuits on a wafer, each of the integrated circuits including a multiplicity of pads; and thereafter partially cutting the wafer, thereby to define notches along outlines of a plurality of inte¬ grated circuit, and wherein the step of partially cutting exposes sectional surfaces of the multiplicity of pads. Preferably the step of partially cutting cuts a plurality of pads including some which communicate with a one of a pair of adjacent integrated circuits and others with communication with another of the pair of adjacent integrated circuits, thereby to define electri¬ cal contact regions for both of said pair of adjacent integrated circuits. In accordance with a preferred embodiment of the present invention there are also provided steps of providing a conductive layer over notched edges of the integrated circuits in electrical communication with the exposed edges of the pads and wherein portions of the conductive layer communicating with separate ones of the multiplicity of pads are electrically separated from one another. In accordance with a preferred embodiment of the present invention, the step of providing a conductive layer comprises forming a conductive coating also over non-edge portions of the integrated circuit. Preferably the partially cutting step is car¬ ried out at locations whereby the silicon substrate is not exposed at the notched edges of the resulting inte¬ grated circuits. In accordance with a preferred embodiment of the present invention, prior to the partially cutting step, the integrated circuits are surrounded on their planar surfaces by protective insulation layers and on their edges by epoxy. Preferably a thermal bonding pad is formed on at least one outer planar surface of said integrated circuit devices. Additionally in accordance with a preferred embodiment of the present invention there is also provid¬ ed the step of providing an integrally formed ground plane in said integrated circuit devices. Preferably, the protective layer is transparent to radiation which is used for erasing EPROM devices. Additionally in accordance with a preferred embodiment of the present invention there is provided apparatus for producing integrated circuit devices in¬ cluding: apparatus for producing a plurality of inte¬ grated circuits on a wafer having opposite planar sur¬ faces, each of the integrated circuits including a multi¬ plicity of pads; apparatus for waferwise attaching to both said surfaces of the wafer a layer of protective packaging material; and partially cutting apparatus for thereafter partially cutting the wafer and the protective material attached thereto, thereby to define notches along out¬ lines of a plurality of prepackaged integrated circuit devices; metal coating apparatus for forming metal contacts onto the plurality of prepackaged integrated circuit devices while they are still joined together on the wafer, at least a portion of the metal contacts extending into the notches; and separating apparatus for thereafter separating the plurality of prepackaged integrated circuit devices into individual devices. Preferably the partially cutting apparatus exposes sectional surfaces of the multiplicity of pads and cuts pads which communicate with adjacent integrated circuits, thereby to simultaneously define electrical contact regions for the adjacent integrated circuits. Further in accordance with a preferred embodi¬ ment of the invention there is provided apparatus for producing integrated circuit devices including: apparatus for producing a plurality of inte¬ grated circuits on a wafer, each of the integrated cir¬ cuits including a multiplicity of pads; and partially cutting apparatus for thereafter partially cutting the wafer, thereby to define notches along " outlines of a plurality of integrated circuit elements which expose sectional surfaces of the multi¬ plicity of pads. Preferably, the partially cutting apparatus cuts a plurality of pads including some which communicate with a one of a pair of adjacent integrated circuits and others with communication with another of the pair of adjacent integrated circuits, thereby to define electri¬ cal contact regions for both of said pair of adjacent integrated circuits. In accordance with a preferred embodiment of the present invention there is also provided apparatus for providing a conductive layer over notched edges of the integrated circuit in electrical communication with the edges of the pads and for electrically separating portions of the conductive layer communicating with separate ones of the multiplicity of pads. Preferably, the conductive layer comprises a conductive coating over more than the edge of the inte¬ grated circuit. Preferably the partially cutting apparatus is operative at locations whereby the silicon substrate is not exposed at the notched edges of the resulting inte¬ grated circuits. Preferably the apparatus of the present inven¬ tion is operative to carry out any and all of the above- mentioned method steps. In accordance with a preferred embodiment of the invention there is provided an integrated circuit device constructed according to a method or using appara¬ tus having any of the foregoing features. Additionally in accordance with a preferred embodiment of the present invention there is provided an integrated circuit device comprising: an integrated circuit die having top and bottom surfaces formed of electrically insulative and mechani¬ cally protective material and electrically insulative edge surfaces having exposed sections of conductive pads and being inclined with respect to the top and bottom surfaces. Additionally in accordance with a preferred embodiment of the present invention, the integrated circuit device includes an integrally formed thermal contact to a heat sink on an outer planar surface of the device and an integrally formed ground plane. Preferably conductive strips are formed on the outside surface of the integrated circuit device for interconnecting the exposed sections of conductive pads at a plurality of edges. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed de¬ scription, taken in conjunction with the drawings in which: Fig. 1 is a simplified pictorial illustration of an integrated circuit device constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 2 is a simplified pictorial illustration of the attachment of a protective packaging layer to a wafer containing a plurality of integrated circuit dies; Fig. 3 is a simplified pictorial illustration of scribing of the wafer to define individual dies, following the attachment of a protective packaging layer to the wafer; Figs. 4A, 4B, 4C, 4D and 4E are sectional illustrations of various stages in the manufacture of integrated circuit devices in accordance with a preferred embodiment of the present invention; Fig. 5 is a partially cut away detailed picto¬ rial illustration of an integrated circuit device pro¬ duced from the wafer of Fig. 4E; Figs. 6, 7 and 8 are sectional illustrations of various stages in the manufacture of the integrated circuit device shown in Figs. 1 & 5; Figs. 9 and 10 together provide a simplified block diagram illustration of apparatus for carrying out the method of the present invention; Fig. 11 is a simplified pictorial illustration of an integrated circuit device constructed and operative in accordance with another preferred embodiment of the present invention and having multiple rows of pads ar¬ ranged on a planar surface thereof; Fig. 12 is a simplified pictorial illustration of an integrated circuit device constructed and operative in accordance with yet another preferred embodiment of the present invention and pads extending to edge surfaces thereof; and Figs. 13, 14 and 15 are sectional illustrations of various stages in the manufacture of the integrated circuit device shown -in. Fig. 12. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference is now made to Figs. 1 - 15, which illustrate the production of integrated circuit devices in accordance with a preferred embodiment of the present invention. Fig. 1 illustrates a preferred embodiment of integrated circuit device constructed and operative in accordance with a preferred embodiment of the present invention and includes a relatively thin and compact, environmentally protected and mechanically strengthened integrated circuit package 10 having a multiplicity of electrical contacts 12 plated along the edge surfaces 14 thereof. In accordance with a preferred embodiment of the invention, contacts 12 extend over edge surfaces onto the planar surfaces 16 of the package. This contact arrange¬ ment permits both flat surface mounting and edge mounting of package 10 onto a circuit board. It is noted that the integrated circuit package 10 may include an integrally formed ground plane (not shown) as well as ground plane contacts 18. In accordance with a preferred embodiment of the present invention, the integrated circuit package 10 may also include one or more thermal bonding pads 19 formed on one or both of the planar surfaces 16 thereof. The provision of such thermal bonding pads 19 is option¬ al. In accordance with a preferred embodiment of the present invention, and as illustrated in Fig. 2 and Fig. 4A, a complete silicon wafer 20 having a plurality of finished dies 22 formed thereon by conventional tech¬ niques, is bonded at its active surface 24 to an insulat¬ ing cover plate 26 via a layer 28 of epoxy. The insulat¬ ing cover plate 26 typically comprises glass, alumina, beryllia, sapphire or any other suitable insulative substrate. to case, however. Reference is now made to Figs. 6, 7 and 8, which illustrate further steps in the manufacture of integrated circuit devices in accordance with a preferred embodiment of the present invention. Fig. 6 illustrates at reference numeral 54, a preferred cross sectional configuration of a notch pro¬ duced by partially cutting as described hereinabove in connection with Fig. 4E. Vertical lines 56 indicate the intersection of the notch 54 with the pads 34, defining exposed sectional pad surfaces 51. Vertical lines 58 indicate the location of a subsequent final cut which separates the dies into individual integrated circuits at a later stage. Fig. 7 illustrates the formation of metal contacts 12 along the inclined edges 14 and part of the top surface 16. These contacts, which may be formed by any suitable metal deposition technique, are seen to extend inside notch 54, thus establishing electrical contact with surfaces 51 of pads 34. It is a particular feature of the present invention that metal contacts are formed onto the dies in electrical contact with surfaces 51 of pads 34 without first separating the dies into individual chips. Fig. 8 illustrates subsequent dicing of the individual dies on the wafer, subsequent to metal contact formation thereon, into individual pre-packaged integrat¬ ed circuit devices. Reference is now made to Figs. 9 and 10, which together illustrate apparatus for producing integrated circuit devices in accordance with a preferred embodiment of the present invention. A conventional wafer fabrica¬ tion facility 180 provides complete wafers 20. Individu¬ al wafers 20 are bonded on their active surfaces by bonding apparatus 182, preferably having facilities for rotation of the wafer 20, the layer 2-6 and the epoxy 28 so as to obtain even distribution of the epoxy. The bonded wafer (Fig. 3) is thinned at its non-active surface as by grinding apparatus 184, such as Model 32BTGW using 12.5A abrasive, which is commercially available from Speedfam Machines Co. Ltd. of England. The wafer is then scribed at its non-active surface by scribing apparatus 186 such as a Kulicke & Soffa 775 dicing saw employing an Ni plated diamond loaded blade, producing a result which is shown in Fig. 4C. The scribed wafer of Fig. 4C is then etched in a temperature controlled bath 188 containing a silicon etch solution 190. Commercially available equipment for this purpose include a Chemkleen bath and an WHRV circu¬ lator both of which are manufactured by Wafab Inc. of the U.S.A.. A suitable conventional silicon etching solution is Isoform Silicon etch, which is commercially available from Micro-Image Technology Ltd. of England. The wafer is conventionally rinsed after etching. The resulting etched wafer is shown in Fig. 4D. The etched wafer is bonded on the non-active side to another protective layer 42 by bonding apparatus 192, which may be essentially the same as apparatus 182, to produce a doubly bonded wafer sandwich as shown in Fig. 4E. Notching apparatus 194, which may be identical to apparatus 186, partially cuts the bonded wafer sand¬ wich of Fig. 4E to a configuration shown in Fig. 5. The notched wafer is then subjected to anti- corrosion treatment in a bath 196, containing a chromat- ing solution 198, such as described in any of the follow¬ ing U.S. Patents: 2,507,956; 2,851,385 and 2,796,370, the disclosure of which is hereby incorporated by reference. Conductive layer deposition apparatus 200, which operates by vacuum deposition techniques, such as a Model 903M sputtering machine manufactured by Material Research Corporation of the U.S.A., is employed to pro¬ duce a conductive layer on one or more surfaces of each die of the wafer as shown in Fig. 7. Configuration of contact strips, as shown in Fig. 7, is carried out preferably by using conventional electro-deposited photoresist, which is commercially available from DuPont under the brand name Primecoat or from Shipley, under the brand name Eagle. The photoresist is applied to the wafers in a photoresist bath assembly 202 which is commercially available from DuPont or Ship¬ ley. The photoresist is preferably laser configured by a suitable laser scanner 204 to define suitable etch¬ ing patterns. The photoresist is then developed in a development bath 206, and then etched in a metal etch solution 208 located in an etching bath 210, thus provid¬ ing a conductor configuration such as that shown in Fig. 1. The exposed conductive strips shown in Fig. 7 are then plated, preferably by electroless plating appa¬ ratus 212, which is commercially available from Okuno of Japan. The wafer is then diced into individual pre¬ packaged integrated circuit devices. Preferably the dicing blade 214 should be a diamond resinoid blade of thickness 4 - 12 mils. The resulting dies appear as illustrated generally in Fig. 1. Reference is now made to Fig. 11, which illus¬ trates a preferred embodiment of integrated circuit device constructed and operative in accordance with another preferred embodiment of the present invention and includes a relatively thin and compact, environmentally protected and mechanically strengthened integrated cir¬ cuit package 310 having a multiplicity of electrical contacts 312 plated along the edge surfaces 314 thereof. Similarly to the embodiment of Fig. 1, contacts 312 extend over edge surfaces onto the planar surfaces 316 of the package. It is a particular feature of the embodiment of Fig. 11, that a relatively large number of contacts 312 is provided on planar surface 316, preferably by arranging them in multiple rows as illustrated. It is seen that the cumulative width of the contacts 312 may be greater than the overall edge length of the chip, without violating design rules. This is accomplished by stagger¬ ing the placement of the contacts 312 as shown. The package may include ground plane contacts 318 as well as one or more thermal bonding pads 319 formed on one or both of the planar surfaces 316 thereof. The provision of such thermal bonding pads 319 is option¬ al. Reference is now made to Fig. 12, which illus¬ trates a preferred embodiment of integrated circuit device constructed and operative in accordance with another preferred embodiment of the present invention and includes a relatively thin and compact, environmentally protected and mechanically strengthened integrated cir¬ cuit package 330 having a multiplicity of electrical contacts 332 plated along the edge surfaces 334 thereof. Similarly to the embodiment of Fig. 11, contacts 332 extend over edge surfaces onto the planar surfaces 336 of the package. A relatively large number of contacts 332 may be provided on planar surface 336, preferably by arranging them in multiple rows as illustrated. In this illustrated embodiment, it is a particular feature that the contacts 332 extend beyond edge 334 onto perpendicu¬ lar edge surfaces 338, which extend perpendicular to planar surface 336. The package may include ground plane contacts 340 as well as one or more thermal bonding pads 342 formed on one or both of the planar surfaces 336 thereof. The provision of such thermal bonding pads 342 is option¬ al.

Claims: C L A I M S 1. A method for producing integrated circuit devices including the steps of: producing a plurality of integrated circuits on a wafer having first and second planar surfaces, each of the integrated circuits including a multiplicity of pads; waferwise attaching to both said surfaces of the wafer a layer of protective material; thereafter partially cutting into the wafer and the protective material attached thereto, thereby to define notches along outlines of a plurality of prepack¬ aged integrated circuit devices; forming metal contacts onto the plurality of prepackaged integrated circuit devices while they are still joined together on the wafer, at least a portion of said metal contacts extending into the notches; and thereafter separating the plurality of prepack¬ aged integrated circuit devices into individual devices. 2. A method according to claim 1 and wherein the step of partially cutting exposes sectional surfaces of the multiplicity of pads. 3. A method according to claim 1 and wherein the step of partially cutting cuts pads so as to simultane¬ ously define electrical contact regions for both of a pair of adjacent integrated circuits. 4. A method for producing integrated circuit devices including the steps of: producing a plurality of integrated circuits on a wafer, each of the integrated circuits including a multiplicity of pads; and thereafter partially cutting the wafer, thereby to define notches along outlines of a plurality of inte¬ grated circuits thereby exposing sectional surfaces of the multiplicity of pads. 5. A method according to claim 4 and wherein the step of partially cutting cuts a plurality of pads including some which communicate with a one of a pair of adjacent integrated circuits and others with communica¬ tion with another of the pair of adjacent integrated circuits, thereby to define electrical contact regions for both of said pair of adjacent integrated circuits. 6. A method according claim 4 and also comprising the steps of providing a conductive layer over notched edges of the integrated circuits in electrical communica¬ tion with the exposed edges of the pads and wherein portions of the conductive layer communicating with separate ones of the multiplicity of pads are electrical¬ ly separated from one another. 7. A method according to claim 6 and wherein the step of providing a conductive layer comprises forming a conductive coating also over non-edge portions of the integrated circuit. 8. A method according to claim 4 and wherein the partially cutting step is carried out at locations where¬ by the silicon substrate is not exposed at the notched edges of the resulting integrated circuits. 9. A method according to claim 4 and wherein prior to the partially cutting step, the integrated circuits are surrounded on their planar surfaces by protective insulation layers and on their edges by epoxy. 10. A method according to claim 4 and wherein a thermal bonding pad is formed on at least one outer planar surface of said integrated circuit devices. 11. A method according to claim 4 and also compris¬ ing the step of providing an integrally formed ground plane in said integrated circuit devices. 12. A method according to claim 10 and wherein said protective insulation layer is transparent to radiation which is used for erasing EPROM devices. 13. A method according to any of the preceding claims and also comprising forming metal contacts in mutually staggered relationship onto a planar surface of said integrated circuit. 14. A method according to any of the preceding claims and also comprising forming metal contacts which extend onto surfaces perpendicular to said first and second planar surfaces. 15. Apparatus for producing integrated circuit devices including: apparatus for producing a plurality of inte¬ grated circuits on a wafer having opposite planar sur¬ faces, each of the integrated circuits including a multi¬ plicity of pads; apparatus for waferwise attaching to both said surfaces of the wafer a layer of protective packaging material; and partially cutting apparatus for thereafter partially cutting the wafer and the protective material attached thereto, thereby to define notches along out¬ lines of a plurality of prepackaged integrated circuit devices; metal coating apparatus for forming metal contacts onto the plurality of prepackaged integrated circuit devices while they are still joined together on the wafer, at least a portion of the metal contacts extending into the notches; and separating apparatus for thereafter separating the plurality of prepackaged integrated circuit devices into individual devices. 16. Apparatus according to claim 15 and wherein the partially cutting apparatus exposes sectional surfaces of the multiplicity of pads and cuts pads which communicate with adjacent integrated circuits, thereby to simultane¬ ously define electrical contact regions for the adjacent integrated circuits. 17. Apparatus for producing integrated circuit devices including: apparatus for producing a plurality of inte¬ grated circuits on a wafer, each of the integrated cir¬ cuits including a multiplicity of pads; and partially cutting apparatus for thereafter partially cutting the wafer, thereby to define notches along outlines of a plurality of integrated circuit elements which expose sectional surfaces of the multi¬ plicity of pads. 18. Apparatus according to claim 17 and wherein the partially cutting apparatus cuts a plurality of pads including some which communicate with a one of a pair of adjacent integrated circuits and others with communica¬ tion with another of the pair of adjacent integrated circuits, thereby to define electrical contact regions for both of said pair of adjacent integrated circuits. 19. Apparatus according to claim 17 and also com¬ prising apparatus for providing a conductive layer over notched edges of the integrated circuit in electrical communication with the edges of the pads and for electri¬ cally separating portions of the conductive layer commu¬ nicating with separate ones of the multiplicity of pads. 20. Apparatus according to claim 19 and wherein the conductive layer comprises a conductive coating over more than the edge of the integrated circuit. 21. Apparatus according to claim 17 and wherein the partially cutting apparatus is operative at locations whereby the silicon substrate is not exposed at the notched edges of the resulting integrated circuits. 22. An integrated circuit device comprising: an integrated circuit die having top and bottom surfaces formed of electrically insulative and mechani¬ cally protective material and electrically insulative edge surfaces having exposed sections of conductive pads and being inclined with respect to the top and bottom surfaces. 23. An integrated circuit device manufactured according to the method of claim 1. 24. An integrated circuit device according to claim 23 and also including at least one of an integrally formed thermal contact to a heat sink on an outer planar surface of the device and an integrally formed ground plane. 25. Apparatus according to any of the preceding claims 15 - 24 and also comprising metal contacts ar¬ ranged in mutually staggered relationship onto a planar surface of said integrated circuit. 26. Apparatus according to any of the preceding claims 15 - 25 and also comprising metal contacts which extend onto surfaces perpendicular to said first an second planar surfaces.

Inventors: BADEHI PIERRE, BADEHI, PIERRE
Applicants: BADEHI PIERRE, SHELLCASE LTD, BADEHI, PIERRE, SHELLCASE LTD.
Application year: 1995
Main classification: H01L23
IPC codes: H01L21, H01L23