ARCHITECTURE FOR FACE-TO-FACE BONDING BETWEEN SUBSTRATE AND MULTIPLE DAUGHTER CHIPS
An integrated circuit system includes a first integrated circuit die and a family of second integrated circuit dice. The first integrated circuit die have input/output circuits disposed thereon and further have a first array of face-to-face bonding structures disposed on a first face thereof. Each member of the family of second integrated circuit dice have logical function circuits disposed thereon and further have a second array of face-to-face bonding structures disposed on a first face thereof. The second array of face-to-face bonding structures of each member of the family mates with a different portion of the first array of face-to-face bonding structures.
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This application is a continuation of co-pending U.S. patent application Ser. No. 11/171,488, filed Jun. 29, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 10/955,929, filed Sep. 29, 2004, which are hereby incorporated by reference as if set forth herein.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to user-programmable integrated circuits. More particularly, the present invention relates to a substrate architecture for face-to-face bonding to multiple daughter chips.
2. The Prior Art
As process geometries scale, the portion of the area of digital-logic function integrated circuits such as field-programmable-gate-array (FPGA) integrated circuits and mixed digital and analog function integrated circuits that must be devoted to input/output (I/O) represents an increasing percentage of the die area relative to logic gates. A secondary cost issue is that often customers may need a significant amount of I/O and not many gates. Presently, such customers end up paying for un-needed gates in order to obtain needed I/O. The reverse is true as well. This represents an opportunity to deliver a more cost-effective product to customers.
Another problem is that some manufacturers envision creating a number of system-on-a-chip (SOC) integrated circuits and derivatives that employ FPGA and other programmable logic technology. These derivatives will have varying quantities and functions of analog peripherals depending on application. Many variations of analog peripherals are envisioned. In addition, the number of FPGA gates needed for each set of peripherals will be customer dependent, again creating a situation where the customer is paying for un-needed gates.
The industry has not come up with a good solution for the I/O problem to date. The current trend is to make several I/O rings and offer variations of products in different combinations with different gate counts. Another solution is to use so-called I/O immersion where I/Os can be programmed anywhere in the FPGA fabric, thereby decoupling the number of I/O circuits from the number of logic gates. This solution however requires flip-chip packaging. Flip-chip packaging is the art of bonding pads distributed anywhere on the face of an IC directly to a package without use of wires. Flip-chip packaging, presently and in the reasonably-foreseeable future, will still add enough cost to the product to offset any cost savings realized from the solution.
The industry in general is looking at a number of so-called 3-D packaging variations. None of these variations are employing 3D packaging to solve the above-described I/O problem.
BRIEF DESCRIPTION OF THE INVENTIONAn integrated circuit system includes a first integrated circuit die and a family of second integrated circuit dice. The first integrated circuit die have input/output circuits disposed thereon and further have a first array of face-to-face bonding structures disposed on a first face thereof. Each member of the family of second integrated circuit dice have logical function circuits disposed thereon and further have a second array of face-to-face bonding structures disposed on a first face thereof. The second array of face-to-face bonding structures of each member of the family mates with a different portion of the first array of face-to-face bonding structures.
According to one aspect of the invention, the first array of face-to-face bonding structures is organized as a plurality of tiles and the second array of face-to-face bonding structures of each member of the family of second integrated circuit dice is an integral number of the tiles.
According to another aspect of the invention, first integrated circuit die may further include circuits other than input/output circuits.
According to another aspect of the invention, there may be more than one first integrated circuit die, each one having a different number of input/output circuits.
According to another aspect of the invention, each member of the family of second integrated circuit dice may have programmable circuits, such as FPGA circuits, disposed thereon, and may further include circuits other than programmable circuits.
Persons of ordinary skill in the art will realize that the following description of the present invention is illustrative only and not in any way limiting. Other embodiments of the invention will readily suggest themselves to such skilled persons.
The present invention employs a low-cost substrate to carry face-to-face mounted daughter chips which can be fabricated in a high-cost state-of-the-art process. The idea is to build an FPGA family in a modular fashion in order to save research and development and non-recurring engineering costs while providing a way to nimbly create derivative parts in response to market conditions.
The I/O circuit portion of an FPGA can be manufactured on mature processes because, among other reasons, a system designer requires higher voltages for signals sent off-chip (e.g., to other components on a printed circuit) board signaling than that needed for the FPGA core. Wafer prices for circuits manufactured using such mature processes are typically steeply discounted relative to leading-edge processes. For example, at a time when 90 nm feature size is the leading edge of FPGA processes, an I/O chip for a 90 nm FPGA device may be produced using a I80 nm process.
According to the present invention, an integrated circuit system includes a plurality of first integrated circuit substrates including I/O circuits, each one having a different I/O count. The I/O circuits may preferably be located on the periphery of the die and are available for wire bonding. The I/O circuits may preferably be fabricated using a mature process node.
The integrated circuit system of the present invention also includes a plurality of second integrated circuit dice. The second integrated circuit dice may include digital programmable logic device circuits, each one having a different gate count. The digital integrated circuits may preferably be fabricated using a leading-edge process node. In addition, the second integrated circuit dice may include circuitry other than digital programmable logic device circuits. For example, such circuits may include volatile and non-volatile memory arrays and other fixed-function digital circuits of any nature.
Face-to-face bonding pads on each of the first and second integrated circuit dice are disposed in the center portion of the first and second integrated circuit die. The face-to-face bonding pads on each of the first and second integrated circuit dice are matingly located with respect to one another and are distributed so that a second integrated circuit die, for example an FPGA which may preferably be fabricated using a leading-edge process so as to minimize cost/gate, can be bonded to the first I/O die. The face-to-face bonding pads may be disposed in a layout pattern that allows different gate-count FPGA integrated circuit die to be face-to-face bonded to different I/O circuit die.
According to the present invention, a device manufacturer can offer customers choices of purchasing various numbers of I/Os for a product with a given gate count, without having to manufacture different versions of that product at the wafer level. In this way, a customer could purchase a product having both a desired gate count and a desired number of I/Os, without having to compromise cost by purchasing an un-needed number of one in order to obtain the desired number of the other. As will be appreciated by persons of ordinary skill in the art, the present invention applies to application specific integrated circuit (ASIC) integrated circuits, system-on-a-chip (SOC) integrated circuits or other functional types of integrated circuits in addition to programmable logic devices such as FPGAs.
Referring first to
The I/O pads 12 are electrically connected to I/O circuits 14. I/O circuits 14 may include buffers, level-shifting circuits and other digital signal conditioning circuitry as is known in the art. The particular composition of the I/O circuits 14 in an integrated circuit fabricated according to the principles of the present invention will be a matter of design choice made by persons of ordinary skill in the art and dictated by the application in which the integrated circuit system of the present invention is used.
Programming registers may be disposed within or coupled to the input/output circuits 14 to define such functions and parameters as is known in the art. As will be appreciated by persons of ordinary skill in the art, such programming registers are in general use in the industry and the loading of the programming registers can be accomplished by using techniques known for programming such programmable registers and programmable logic devices in general. Such techniques include, but are not limited to, coupling the registers together to a JTAG port on the integrated circuit die 10 that is coupled to the input/output pads, coupling the registers to other circuitry to be programmed and located on the integrated circuit die 10 or on the integrated circuit to be mated with the input/output circuit integrated circuit die 10. The registers could be coupled to, for example, an FPGA programming circuit contained on the integrated circuit die 10 or on the logic-function integrated-circuit die to which the integrated circuit die 10 of
Depending on the I/O density required by the application, the input/output circuits 14 may be arranged in more than one concentric “ring” with the outermost one of the rings being located inward from the edges of the integrated circuit die, and the next ring being located inward of the input/output circuits in the outer ring.
The particular layout used for the input/output circuits on the substrate 10 of the present invention is a matter of design choice but it is presently preferred to group pluralities of such circuits into I/O “tiles” as will be disclosed with reference to
Also included on input/output integrated circuit die 10 is a daughter-die mounting area 16 containing a plurality of arrays of face-to-face bonding pads. In
As shown in
Referring now to
In the embodiment shown in
Another type of tile is an I/O tile 40. Each I/O tile 40 includes a plurality of the input/output circuits 14 of
A third type of tile is shown in
In the embodiments shown in
A tile type designated as “other” 46 allows other types of circuit functions to be integrated into the system of the present invention. There is virtually no limit to the additional types of circuits providing different analog, digital, and mixed analog and digital functions that can be tiled into the present invention for use in the various sized substrates 30, 32, 34, and 36. A non-exhaustive list of such circuits includes, analog system-on-a-chip type circuits, large SRAM blocks, DSP circuits, CPU and other microcontroller circuits, high-speed busses, such as VSIA, Sonics, etc.
Persons of ordinary skill in the art will observe that the various tiles preferably have the same form factor. This allows the entire family of integrated circuit substrates to be designed using the same tile block layouts, thus producing significant design-cost savings. For example, persons of ordinary skill in the art will observe that the non-volatile memory programming circuits 46 are the same tile size in the embodiments of
Persons skilled in the art will also appreciate that, since the CCTs 38 are interconnects that use almost no silicon area on the substrate, the CCT substrate area can be used for other circuitry, such as the non-volatile memory circuitry, which will vary in size as a function as the number of CCTs 38 used on a substrate. This means that a lot of silicon area in the CCTs is free to implement analog overhead, CPUs, SRAMs, PROMs, DSPs, logic IPS, etc.
The other component in the system of the present invention is a family of daughter chips.
The daughter chips can be any size that is an integer multiple of the size in the X direction and the Y direction of the CCTs 38 on the substrates. The daughter chips match up with the CCTs 38 of
Referring first to
In addition, the 3×3 CCT group of FPGA tiles of
Similar illustrative groups of FPGA tiles are shown in
In
In
Finally, in
Persons of ordinary skill in the art will appreciate that the configurations for the daughter chips shown in
As may be understood from an examination of
When the versatility of the daughter chip arrangements of the present invention is combined with the versatility of the substrate components, the possibilities increase dramatically. For example, the substrate of
Referring now to
According to another aspect of the present invention, daughter chips like those of
While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications than mentioned above are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.
Claims
1. An integrated circuit system including:
- a first integrated circuit die having input/output circuits disposed thereon and further having a first array of face-to-face bonding structures disposed on a first face thereof;
- a family of second integrated circuit dice, each member of the family having logical function circuits disposed thereon and each member of the family further having a second array of face-to-face bonding structures disposed on a first face thereof, the second array of face-to-face bonding structures of each member of the family mates with different portion of the first array of face-to-face bonding structures.
Type: Application
Filed: Apr 14, 2008
Publication Date: Aug 14, 2008
Applicant: ACTEL CORPORATION (Mountain View, CA)
Inventors: William C. Plants (Campbell, CA), John McCollum (Saratoga, CA), Theodore Speers (San Jose, CA)
Application Number: 12/102,765
International Classification: H01L 23/48 (20060101);