1. Field of the Invention
This invention relates generally to a method and apparatus for dicing or sawing semiconductor substrates having encapsulated semiconductor devices thereon and more specifically to a saw and chuck and method of using the same employing using multiple indexing techniques and multiple blades for more efficient sawing from an array of semiconductor devices on a substrate.
2. State of the Art
An individual integrated circuit semiconductor device, semiconductor die, or chip is usually formed from a larger structure known as a semiconductor wafer, which is usually comprised primarily of silicon, although other materials such as gallium arsenide and indium phosphide are also sometimes used. Each semiconductor wafer has a plurality of integrated circuits arranged in rows and columns with the periphery of each integrated circuit being rectangular. Typically the wafer is sawn or “diced” into rectangularly shaped discrete integrated circuits along two mutually perpendicular sets of parallel lines or streets lying between each of the rows and columns thereof. Hence, the separated or singulated integrated circuits are commonly referred to as dice.
One exemplary wafer saw includes a rotating dicing blade mounted to an aluminum hub and attached to a rotating spindle, the spindle being connected to a motor. Cutting action of the blade may be effected by diamond particles bonded thereto, or a traditional “toothed” type blade may be employed. Many rotating wafer saw blade structures are known in the art. The present invention is applicable to any saw blade construction so further structures will not be described herein.
Because semiconductor wafers in the art usually contain a plurality of substantially identical integrated circuits arranged in rows and columns, two sets of mutually parallel streets extending perpendicular to each other over substantially the entire surface of the wafer are formed between each discrete integrated circuit and are sized to allow passage of a wafer saw blade between adjacent integrated circuits without affecting any of their internal circuitry. Prior to the sawing of a semiconductor wafer to singulate the wafer and to create individual semiconductor die from the wafer, a piece of tape, typically referred to as wafer tape, is applied to the back side of the wafer so that once the wafer has been singulated, the individual semiconductor die remain attached to the wafer tape for further handling and processing.
Once the wafer tape has been applied to the back side of the wafer, a typical wafer sawing operation includes attaching the semiconductor wafer to a wafer saw carrier, mechanically, adhesively or otherwise as known in the art and mounting the wafer saw carrier on the table of the wafer saw. A blade of the wafer saw is passed through the surface of the semiconductor wafer, either by moving the blade relative to the wafer, the table of the saw and the wafer relative to a stationary blade, or a combination of both. To dice the wafer, the blade cuts precisely along each street, returning back over (but not in contact with) the wafer while the wafer is laterally indexed to the next cutting location. Once all cuts associated with mutually parallel streets having one orientation are complete, either the blade is rotated 90° relative to the wafer or the wafer is rotated 90°, and cuts are made through streets in a direction perpendicular to the initial direction of cut. Since each integrated circuit on a conventional wafer has the same size and rectangular configuration, each pass of the wafer saw blade is incrementally indexed one unit (a unit being equal to the distance from one street to the next) in a particular orientation of the wafer. As such, the wafer saw and the software controlling it are designed to provide uniform and precise indexing in fixed increments across the surface of a wafer.
Once the individual or singulated semiconductor die have been sawed, the semiconductor die are further processed by being removed from the wafer tape, attached to substrates and packaged, such as the semiconductor die being adhesively attached to a substrate in a board-over-chip configuration (BOC), connections made between the semiconductor die and the circuits of the substrate by wire bonding, and the semiconductor die and portions of the substrate being encapsulated. While the semiconductor die and substrate may be individually handled, it is more efficient to process a plurality of semiconductor die, each semiconductor die being individually mounted, on a substrate having a configuration providing for each individually mounted semiconductor die thereon and circuits for connection with each individually semiconductor die as well as for the encapsulation of each individual semiconductor die mounted on the substrate.
However, existing process equipment and apparatus do not have the capability of singulating the packaged semiconductor die on a substrate when a plurality of semiconductor die are contained in an array on a substrate.
Accordingly, an apparatus and method for sawing semiconductor substrates, including substrates having a plurality of semiconductor devices of different sizes and/or shapes therein, is provided. In particular, the present invention provides a saw and method of using the same capable of “multiple indexing” of a saw blade or blades to provide the desired cutting capabilities. As used herein, the term “multiple indexing” contemplates and encompasses both the lateral indexing of a saw blade at multiples of a fixed interval and at varying intervals which may not comprise exact multiples of one another. Thus, for conventional substrate and/or wafer configurations containing a number of equally sized integrated circuits, the wafer saw and method herein can substantially simultaneously saw the substrates and/or wafers with multiple blades and therefore cut more quickly than single blade wafer saws known in the art. Moreover, for wafers having a plurality of differently sized or shaped integrated circuits, the apparatus and method herein provides a multiple indexing capability to cut nonuniform dice from the same wafer.
The present invention includes a substrate chuck mounted on a table used in conjunction with the saw for holding a substrate having an array of encapsulated semiconductor devices mounted thereon for singulation. The chuck comprises a chuck table, at least one cutting pedestal, at least one clamp, at least one clamp pedestal, and an alignment apparatus for aligning a substrate for singulation in the chuck. The alignment apparatus may comprise at least one alignment pin having a portion thereof attached to the chuck table and having a portion engaging the substrate to be singulated or a recess in the chuck table for receiving the substrate to be singulated therein.
In one embodiment, a single-blade, multi-indexing saw is provided for cutting a substrate containing variously configured semiconductor devices thereon which may be encapsulated. By providing multiple-indexing capabilities, the saw can sever the wafer into differently sized mounted encapsulated semiconductor devices corresponding to the configuration of the semiconductor devices contained thereon.
In another embodiment, a saw is provided having at least two wafer saw blades spaced a lateral distance from one another and having their centers of rotation in substantial parallel mutual alignment. The blades are preferably spaced apart a distance equal to the distance between adjacent areas for cutting the substrate. With such a saw configuration, multiple parallel cuts through the substrate can be made substantially simultaneous, thus essentially increasing the speed of cutting a substrate by the number of blades utilized in tandem. Because of the small size of the individual semiconductor devices mounted and/or encapsulated on the substrate and the correspondingly small distances between adjacent cutting areas on the substrate, it may be desirable to space the blades of the saw more than one cutting area apart. For example, if the blades of a two-blade saw are spaced two cutting areas apart, a first cut would cut the first and third laterally separated cutting areas. A second pass of the blades through the substrate would cut through the second and fourth streets. The blades would then be indexed to cut through the fifth and seventh streets, then sixth and eighth, and so on.
In yet another embodiment, at least one blade of a multi-blade saw is independently raisable relative to the other blade or blades when only a single cut is desired on a particular pass of the carriage. Such a saw configuration has special utility where the blades are spaced close enough to cut in parallel on either side of larger encapsulated semiconductor devices, but use single blade capability for dicing any smaller integrated circuits. For example, a first pass of the blades of a two-blade saw could cut a first set of adjacent cutting areas of the substrate defining a column of larger semiconductor devices on the substrate. One blade could then be independently raised or elevated to effect a subsequent pass of the remaining blade cutting along a cutting area of the substrate that may be too laterally close to an adjacent street to allow both blades to cut simultaneously, or that merely defines a single column of narrower semiconductor devices. This feature would also permit parallel scribing of the surface of the substrate to mutually isolate conductors from, for example, tie bars or other common links required during fabrication, with subsequent passage by a single blade indexed to track between the scribe lines to completely sever or singulate the adjacent portions of the substrate.
In still another embodiment, at least one blade of a multi-blade saw is independently laterally translatable relative to the other blade or blades. Thus, in a two-blade saw, for example, the blades could be laterally adjusted between consecutive saw passes of the sawing operation to accommodate different widths between cutting areas of the substrate. It should be noted that this embodiment could be combined with other embodiments herein to provide a wafer saw that has blades that are both laterally translatable and independently raisable, or one translatable and one raisable, as desired.
As illustrated in drawing
The saw 10 is capable of lateral multi-indexing of the table 22 having a chuck 500 or blade 18 or, in other words, translatable from side-to-side in drawing
Before proceeding further, it will be understood and appreciated that design and fabrication of a substrate saw for use with the present invention having the previously referenced, multi-indexing capabilities, independent lateral blade translation and independent blade raising or elevation is within the ability of one of ordinary skill in the art, and that likewise, the control of such a device to effect the multiple-indexing (whether in units of fixed increments or otherwise), lateral blade translation and blade elevation may be effected by suitable programming of the software-controlled operating system, as known in the art. Accordingly, no further description of hardware components or of a control system to effectuate operation of the apparatus of the invention is necessary.
Referring now to drawing
As illustrated in drawing
Finally, it may be desirable to combine the lateral translation feature of the embodiment of the substrate saw 30 illustrated in drawing
It will be appreciated by those skilled in the art that the embodiments herein described while illustrating certain embodiments are not intended to so limit the invention or the scope of the appended claims. More specifically, this invention, while being described with reference to substrates for semiconductor devices thereon, either encapsulated or not, semiconductor wafers containing integrated circuits or other semiconductor devices, has equal utility to any type of substrate to be scribed or singulated. For example, fabrication of test inserts or chip carriers formed from a silicon (or other semiconductor substrate) or wafer and used to make temporary or permanent chip-to-wafer, chip-to-chip, and chip-to-carrier interconnections and that are cut into individual or groups of inserts, as described in U.S. Pat. Nos. 5,326,428 and 4,937,653, may benefit from the multi-indexing method and apparatus described herein.
For example, illustrated in drawing
As shown in drawing
Further, the saw used with the present invention has particular applicability to the fabrication of custom or nonstandard integrated circuits or other components, wherein a capability for rapid and easy die size and shape adjustment on a substrate-by-substrate or wafer-by-wafer basis is highly beneficial and cost-effective. In the present saw it may be desirable to have at least one blade of the independently laterally translatable blade configuration be independently raisable relative to the other blade or blades, or a single blade may be both translatable and raisable relative to one or more other blades and to the target substrate or wafer. In addition, while for purposes of simplicity, some of the preferred embodiments of the substrate saw are illustrated as having two blades, however, the saw may have more or less than two blades.
Referring to drawing
Referring to drawing
Referring to drawing
Referring to drawing
Each of the cutting pedestals 504 is spaced from an adjacent cutting pedestal 504 by a space 503 and space 505 which also extends both between the cutting pedestals 504 and one the exterior of the cutting pedestals 504 to allow a saw blade 18 of a saw as described herein to cut a substrate 40 into the desired number of singulated semiconductor devices 42, each singulated semiconductor device 42 having a plurality of connectors 306 attached to one side thereof. In this manner, an array of any desired number of semiconductor devices 42 on a substrate 40 may be retained in the chuck 500 to be singulated by a saw 10 having one or more blades 18. Additionally, since the depth and width of a saw 10 may vary, any spacing of the semiconductor devices 42 on the substrate 40 may be used.
Referring to drawing
The chuck 500 and 500′ of the present invention may include alterations and features, changes, additions, and deletions which are intended to be within the scope of the invention. For instance, the chuck may be of any size, shape, and configuration. The chuck may have any desired number of cutting pedestals of any size, shape, and configuration thereon, may have any desired number, shape, size, and configuration of clamps and clamp pedestals, may have any desired alignment apparatus for a substrate thereon, etc.
Thus, while certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes in the invention disclosed herein may be made without departing from the scope of the invention, which is defined in the appended claims.
This application is a divisional of application Ser. No. 10/643,455, filed Aug. 19, 2003, pending, which is a divisional of application Ser. No. 09/875,063 filed Jun. 6, 2001, pending.
Number | Date | Country | |
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Parent | 10643455 | Aug 2003 | US |
Child | 11281695 | Nov 2005 | US |
Parent | 09875063 | Jun 2001 | US |
Child | 10643455 | Aug 2003 | US |