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Multi-chip stacked devices |
| RE40061 |
Multi-chip stacked devices
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| Patent Drawings: | |
| Inventor: |
Ball |
| Date Issued: |
February 12, 2008 |
| Application: |
10/346,860 |
| Filed: |
January 16, 2003 |
| Inventors: |
Ball; Michael B. (Boise, ID)
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| Assignee: |
Micron Technology, Inc. (Boise, ID) |
| Primary Examiner: |
Potter; Roy |
| Assistant Examiner: |
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| Attorney Or Agent: |
TraskBritt |
| U.S. Class: |
438/109; 257/676; 257/686; 257/782; 257/783; 438/118; 438/123; 438/438 |
| Field Of Search: |
438/123; 438/109; 257/686; 257/782; 257/783; 257/676 |
| International Class: |
H01L 23/48 |
| U.S Patent Documents: |
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| Foreign Patent Documents: |
56-62351; 56-62351; 60-182731; 62-126661; 63-128736; 1-28856; 3-169062; 4-56262 |
| Other References: |
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| Abstract: |
A multiple stacked die device is disclosed that contains up to four dies and does not exceed the height of current single die packages. Close-tolerance stacking is made possible by a low-loop-profile wire-bonding operation and thin-adhesive layer between the stacked dies. |
| Claim: |
What is claimed is:
.[.1. A multiple-die low-profile semiconductor device comprising: a. a lead-frame paddle supported by a lead frame; b. a controlled, first, thin-adhesive layer of about0.001 inches affixing a first die above the paddle; c. a plurality of thin wires having a first low-loop wire bond to a plurality of first diebonding pads, said wire bond having a wire height above the bonding pad of about 0.006 inches, and a secondwire bond to a plurality of adjacent lead-frame lead fingers; d. a second thin-adhesive layer of about 0.008 inches affixing a second die above the first die; e. a second plurality of thin wires having low-loop wire bonds to a plurality of seconddie-bonding pads and second wire bonds to the plurality of lead fingers; f. two additional dies affixed above the second die by additional subsequent layers of adhesive of about 0.008 inches and having additional thin wires bonded to additional bondingpads and lead fingers; and g. an encapsulated layer surrounding all dies, adhesive layers, and thin wires wherein a total encapsulated-package height is about 0.110 inches..].
.[.2. A multiple-die low-profile semiconductor device comprising: a. a lead-frame paddle supported by a lead frame; b. a controlled, first, thin-adhesive layer of about 0.001 to 0.005 inches affixing a first die above the paddle; c. aplurality of thin wires having a first low-loop wire bond to a plurality of first die-bonding pads, said low-loop wire ball bond having a wire height above the bonding pads of about 0.006 inches and a second wire bond to a plurality of adjacentlead-frame lead fingers; d. a second thin-adhesive layer of about 0.008 to 0.010 inches affixing a second die above the first die; e. a second plurality of thin wires having low-loop wire bonds to a plurality of second die-bonding pads and second wirebonds to the plurality of lead fingers; f. an encapsulated layer surrounding all die adhesive layers and thin wires wherein a total encapsulation-layer height is about 0.070 inches..].
.Iadd.3. A method for fabricating a multiple-die, low-profile semiconductor device, comprising:.Iaddend. .[.a..]. .Iadd.providing a lead frame having a lead frame paddle and a plurality of lead fingers;.Iaddend. .[.b..]. .Iadd.affixing tosaid paddle a first die having a plurality of first die-bonding pads;.Iaddend. .[.c..]. .Iadd.connecting bond wires between each of said plurality of first die-bonding pads and corresponding lead fingers of said plurality of lead fingers by way of alow-loop wire bond on each of said plurality of first die-bonding pads and a wire bond on each of said corresponding lead fingers;.Iaddend. .[.d..]. .Iadd.affixing to said first die, following said connecting bond wires, a second die having a pluralityof second die-bonding pads;.Iaddend. .[.e..]. .Iadd.connecting bond wires between each of said plurality of second die-bonding pads and corresponding lead fingers of said plurality of lead fingers by way of a low-loop wire bond on each of saidplurality of second die-bonding pads and a wire bond on each of said corresponding lead fingers; and.Iaddend. .[.f..]. .Iadd.affixing two additional dies above said second die..Iaddend.
.Iadd.4. The method of claim 3, further comprising encapsulating all dies and bond wires with an encapsulation layer having a height of about 0.110 .Iaddend..[.inches.]. .Iadd.inch..Iaddend.
.Iadd.5. The method of claim 3, wherein die-bonding pads of said first plurality of die-bonding pads are connected to said corresponding lead fingers of said plurality of lead fingers in parallel with die-bonding pads of said second pluralityof die-bonding pads..Iaddend.
.Iadd.6. The method of claim 3, wherein die-bonding pads of said first plurality of die-bonding pads and die-bonding pads of said second plurality of die-bonding pads are each connected to individual ones of said plurality of leadfingers..Iaddend.
.Iadd.7. The method of claim 3, wherein said providing comprises providing a lead frame having a downset lead frame paddle and a plurality of lead fingers upset relative to said downset lead frame paddle..Iaddend.
.Iadd.8. The method of claim 3, wherein said connecting bond wires between each of said first and second pluralities of die-bonding pads and corresponding ones of said lead fingers comprises forming said low-loop wire bonds on each of saiddie-bonding pads to be ball bonds..Iaddend.
.Iadd.9. The method of claim 3, wherein said connecting bond wires between each of said first and second pluralities of die-bonding pads and corresponding ones of said lead fingers comprises forming said wire bonds on each of said correspondinglead fingers to be wedge bonds..Iaddend.
.Iadd.10. The method of claim 3, wherein said affixing said first die to said lead frame paddle comprises disposing a layer of adhesive between said lead frame paddle and said first die..Iaddend.
.Iadd.11. The method of claim 10, wherein said disposing said layer of adhesive comprises forming said layer of adhesive to be about 0.001 .Iaddend..[.inches.]. .Iadd.inch .Iaddend.thick.
.Iadd.12. The method of claim 3, wherein said affixing said second die to said first die comprises disposing a layer of adhesive between said first die and said second die..Iaddend. |
| Description: |
FIELD OF THE INVENTION
This invention relates to a multiple die module that has a thickness the same or less than a standard package but has two or more stacked die, thereby increasing device density.
BACKGROUND OF THE INVENTION
Semiconductor devices are typically constructed en masse on a silicon or gallium arsenide wafer through a process which comprises a number of deposition, masking, diffusion, etching, and implanting steps. When the devices are sawed intoindividual rectangular units, each takes the form of an integrated circuit (IC) die. In order to interface a die with other circuitry, it is (using contemporary conventional packaging technology) mounted on a lead frame paddle of a lead-frame stripwhich consists of a series of interconnected lead frames, typically ten in a row. The die-mounting paddle of a standard lead frame is larger than the die itself, and it is surrounded by multiple lead fingers of individual leads. The bonding pads of thedie are then connected one by one in a wire-bonding operation to the lead frame's lead finger pads with extremely fine gold or aluminum wire. Following the application of a protective layer to the face of the die, it, and a portion of the lead frame towhich it is attached, is encapsulated in a plastic material, as are all other die/lead-frame assemblies on the lead-frame strip. A trim-and-form operation then separates the resultant interconnected packages and bends the leads of each package into theproper configuration.
In the interest of higher performance equipment and lower cost, increased miniaturization of components and greater packaging density have long been the goals of the computer industry. IC package density is primarily limited by the areaavailable for die mounting and the height of the package. Typical computer-chip heights in the art are about 0.110 .[.inches.]. .Iadd.inch.Iaddend.. A method of increasing density is to stack die or chips vertically.
U.S. Pat. No. 5,012,323, issued Apr. 30, 1991, having a common assignee with the present application, discloses a pair of rectangular integrated-circuit dice mounted on opposite sides of the lead frame. An upper, smaller die is back-bonded tothe upper surface of the lead fingers of the lead frame via a first adhesively coated, insulated film layer. The lower, slightly larger die is face-bonded to the lower surface of the lead extensions within the lower lead-frame die-bonding region via asecond, adhesively coated, insulative, film layer. The wire-bonding pads on both upper die and lower die are interconnected with the ends of their associated lead extensions with gold or aluminum wires. The lower die needs to be slightly larger inorder that the die pads are accessible from above so that gold wire connections can be made to the lead extensions (fingers).
U.S. Pat. No. 4,996,587 (referred to hereafter as '587) shows a semiconductor chip package which uses a chip carrier to support the chips within a cavity. The chip carrier as shown in the figures has a slot that permits connection by wires tobonding pads which, in turn, connect to the card connector by conductors. An encapsulation material is placed only on the top surface of the chip in order to provide heat dissipation from the bottom surface when carriers are stacked.
A Japanese Patent No. 56-62351(A) issued to Sano in 1981 discloses three methods of mounting two chips on a lead frame and attaching the pair of semiconductor chips (pellets) to a common lead frame consisting of: method 1 two chips mounted on twopaddles; method 2 one chip mounted over a paddle and one below not attached to the paddle; and method 3 one chip attached above and one chip attached below a common paddle. The chips are apparently wired in parallel as stated in the "PURPOSE" of Sano.
The chips of patent '587 are also apparently wired in parallel by contacts on the "S" chips which contact the connection means.
It is the purpose of this invention to provide multiple stacked dies assembled in a special vertical configuration such that as many as four encapsulated dies will have a height no greater than existing 0.110-inch high dies and also have aseparate lead and lead finger for each die pad connection.
SUMMARY OF THE INVENTION
The invention generally stated is a multiple-die low-profile semiconductor device comprising: a lead-frame paddle supported by a lead frame; a controlled, first, thin-adhesive layer affixing a first die above the paddle; a plurality of thin wireshaving a first low-loop wire bond to a plurality of first die-bonding pads and a second wire bond to a plurality of adjacent lead-frame lead fingers; a second thin-adhesive layer affixing a second die above the first die; a second plurality of thin wireshaving low-loop wire bonds to a plurality of second die-bonding pads and second wire bonds to the plurality of lead fingers; additional dies affixed above the second die, by additional subsequent layers of adhesive and having additional thin wires bondedto .[.addition.]. .Iadd.additional .Iaddend.bonding pads and lead fingers; and an encapsulated layer surrounding all dies, adhesive layers, and thin wires.
Other objects, advantages, and capabilities of the present invention will become more apparent as the description proceeds.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be better understood and further advantages and uses thereof may become more readily apparent when considered in view of the following detailed description of exemplary embodiments, taken with the accompanied drawings, in which:
FIG. 1 is a partial plan view of the stacked die, lead fingers, and bonded wires of the present invention; and
FIG. 2 is a side elevation taken through lines 2--2 of FIG. 1 showing a four die stacking.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, the stacked die device 10 is shown prior to encapsulation disclosing the top die 12 mounted .[.upon.]. .Iadd.to .Iaddend.the paddle 14 and other dies 16, 18, and 20 (FIG. 2) which are adhesively connected to each other by acontrolled-thickness thermoplastic-adhesive layer at 22. .[.Thermoplastic indicating.]. .Iadd."Thermoplastic" indicates that .Iaddend.the adhesive sets at an elevated temperature. The group of four dies are attached to the paddle 14 by a controlledthin-adhesive layer 24.
Each of the die bonding pads 26 in double rows are electrically connected to multiple lead fingers 28A, 28B, 28C . . . 28N by thin (0.001 inch) gold or aluminum wires 30A, 30B, 30C . . . 30N; gold being the preferred metal. For clarity, onlypart of the 18 bonding pads, wires, and fingers are shown. The critical bonding method used at the die end pad 26 is an ultrasonic ball .[.bond.]. .Iadd.bond, .Iaddend.as named by the shape of the bond as at 32. This first-installed bond and formedgold wire are low-loop wire bonds as seen at critical dimension 34, as will be described later.
The other end of gold wires 30 are attached to the lead fingers by a wedge bond 36, which is also an ultrasonic bond, indicating the use of ultrasonic energy to heat the wire 30 as it is compressed against the lead finger 28. The wedge bond isnot used on the die because the bonding machine contacts the bonding surface and could damage this critical surface. The lead fingers may be formed upward as at 38 to permit the use of shorter wires 30.
Paddle 14 which supports the stack is attached to the lead frame typically at four corners as at 40 and also typically, in this application, would have a downset from the lead frame and lead fingers 28 as at dimension 42. The stack is finallyencapsulated by a plastic or ceramic at 44.
A dimensional analysis is provided by referring to FIG. 2.
By careful control of layer thicknesses, it is possible to fabricate a four-stack die device having an overall height 46 of about 0.110 .[.inches.]. .Iadd.inch .Iaddend.which is the same height as a current single die. Starting at the bottom,the encapsulation thickness 48 is between 0.010 and 0.012 .[.inches.]. .Iadd.inch.Iaddend.. The paddle .[.74.]. .Iadd.14 .Iaddend.thickness 50 can be between 0.005 and 0.010 .[.inches.]. .Iadd.inch .Iaddend.and is a matter of choice. The controlledadhesive-layer thickness 52 can be from 0.001 to 0.005 .[.inches.]. .Iadd.inch.Iaddend.. The individual dies 20, 18, 16, and 12 each have a thickness 54 of 0.012 .[.inches.]. .Iadd.inch .Iaddend.and the critical controlled, adhesive-layer thicknesses56 between each die are between 0.008 and 0.010 .[.inches.]. .Iadd.inch.Iaddend.. These thin layers have to be slightly greater than the low-loop wire dimension 34, which is about 0.006 .[.inches.]. .Iadd.inch.Iaddend.. Finally, the top encapsulationthickness 58 is between 0.010 and 0.012 .[.inches.]. .Iadd.inch .Iaddend.so as to cover the top loop.
Thus, it can be seen by carefully controlling and minimizing the adhesive layer thicknesses 56, the top and bottom encapsulation thicknesses 48 and 58, and the paddle adhesive layer 52 that it is possible to have an overall height between 0.108and 0.110 .[.inches.]. .Iadd.inch .Iaddend.overall for the four-stack die.
If the looser tolerances were used for a two-stack die, the height at 60 would be between 0.058 and 0.073 .[.inches.]. .Iadd.inch .Iaddend.and for a three-die stack it would be from 0.078 to 0.100 .[.inches.]. .Iadd.inch.Iaddend..
The fabrication of these two or four-stack die devices, necessarily, has to be from the bottom up, since it is not possible to form the die pad wire ball bond 32 on the lower dies 16, 18, and 30, if the four dies are already stacked. This is dueto the overhead space required by the wire bond machine.
The die pads 26 of each die can be each connected to an individual lead finger 28 or the dies can be wired in parallel. The former configuration would, therefore, require (for a four die stack) something less than .[.4.times.18=72 .]..Iadd.4.times.18=72 .Iaddend.leads, while parallel connections would require something on the order of 22 or more pins, depending on the type of devices and system requirements. The final packages can be in the form of a small outline J-leaded (SOJ)package, a dual in-line package (DIP), a single in-line package (SIP), a plastic leaded chip carrier (PLCC), and a zig-zag in-line package (ZIP).
While a preferred embodiment of the invention has been disclosed, various modes of carrying out the principles disclosed herein are contemplated as being within the scope of the following claims. Therefore, it is understood that the scope of theinvention is not to be limited except as otherwise set forth in the claims.
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