Classifications

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  • H01L25/04—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
  • H01L25/065—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H10D89/00
  • H01L25/0657—Stacked arrangements of devices
• • G—PHYSICS
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  • G11C5/00—Details of stores covered by group G11C11/00
  • G11C5/02—Disposition of storage elements, e.g. in the form of a matrix array
• • G—PHYSICS
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  • G11C5/00—Details of stores covered by group G11C11/00
  • G11C5/06—Arrangements for interconnecting storage elements electrically, e.g. by wiring
  • G11C5/066—Means for reducing external access-lines for a semiconductor memory clip, e.g. by multiplexing at least address and data signals
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
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  • H01L24/02—Bonding areas ; Manufacturing methods related thereto
  • H01L24/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
  • H01L24/06—Structure, shape, material or disposition of the bonding areas prior to the connecting process of a plurality of bonding areas
• • G—PHYSICS
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  • G11C16/00—Erasable programmable read-only memories
  • G11C16/02—Erasable programmable read-only memories electrically programmable
  • G11C16/06—Auxiliary circuits, e.g. for writing into memory
• • G—PHYSICS
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  • G11C19/00—Digital stores in which the information is moved stepwise, e.g. shift registers
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  • H01L2224/02—Bonding areas; Manufacturing methods related thereto
  • H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
  • H01L2224/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
  • H01L2224/0554—External layer
  • H01L2224/0555—Shape
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  • H01L2225/03—All the devices being of a type provided for in the same main group of the same subclass of class H10, e.g. assemblies of rectifier diodes
  • H01L2225/04—All the devices being of a type provided for in the same main group of the same subclass of class H10, e.g. assemblies of rectifier diodes the devices not having separate containers
  • H01L2225/065—All the devices being of a type provided for in the same main group of the same subclass of class H10
  • H01L2225/06503—Stacked arrangements of devices
  • H01L2225/06513—Bump or bump-like direct electrical connections between devices, e.g. flip-chip connection, solder bumps
• • H—ELECTRICITY
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  • H01L2225/03—All the devices being of a type provided for in the same main group of the same subclass of class H10, e.g. assemblies of rectifier diodes
  • H01L2225/04—All the devices being of a type provided for in the same main group of the same subclass of class H10, e.g. assemblies of rectifier diodes the devices not having separate containers
  • H01L2225/065—All the devices being of a type provided for in the same main group of the same subclass of class H10
  • H01L2225/06503—Stacked arrangements of devices
  • H01L2225/06541—Conductive via connections through the device, e.g. vertical interconnects, through silicon via [TSV]
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  • H01L2924/11—Device type
  • H01L2924/14—Integrated circuits

Definitions

• the present invention relates generally to integrated circuits, or chips.
• the present invention relates to the arrangement of chip connections for chip stacking.
• MCPs Multi Chip Packages
• each chip should be disposed to have enough spacing, which results in a form factor increase. Bonding wire technology can also reduce the mechanical durability of the MCP from the wires being at odd angles.
• wire bonding requires spacers for each chip. This results in increased height of the stack, which makes the handling and the assembly of the integrated device stack more challenging compared to stacks that do not comprise spacers. Also, the length of the bond wires is greater in a chip stack having spacers, which leads to a reduced electrical performance of the chip stack system. Furthermore, the thermal resistance of an integrated device stack having a spacer in the integrated device chips is increased.
• Another approach is to use a via between chips.
• the through chip via can be a better approach to resolve the issue of noise from the electrical characteristics.
• Fig. 1 shows a partial top view 102 and cross-section view 104 of a conventional multi-chip stack or multi-chip device 100 made using through-chip via technology.
• a plurality of signal pads A1-A6 and B1-B6 are shown, which facilitate connection of internal and external signals to the chip.
• the vias themselves are not seen in the top view.
• the cross section-view 104 is taken along line A-A in the top view.
• the through chip via method used in Fig. 1 relates to common input or output connections, or parallel connections. Because of this, the only real fabrication issue was how deeply clean holes could be drilled and made to connect the same pins to each other as a common connection. In the case of multi-drop connections among same memory chips, the alignment of each chip is so important that all chips are aligned without a pad spacer, which is required in the bonding wire connection for multi-chip packaging.
• the present invention provides a multi-chip device including a stacked pair of integrated circuit chips comprising a top chip and a bottom chip.
• the top chip has one or more input signal pads for connection to external input signals and one or more common connection signal pads.
• Each common connection signal pad is symmetrically disposed on or about a center line of the top chip with respect to a duplicate common connection signal pad.
• One or more output signal pads are symmetrically disposed about the center line of the top chip with respect to respective input signal pads.
• the bottom chip has a substantially identical signal pad arrangement as the top chip, the bottom chip being flipped in orientation with respect to the top chip.
• the device includes a parallel connection through-chip via connecting a top chip common connection signal pad in parallel with its duplicate common connection signal pad.
• the device also includes a serial connection through-chip via connecting a top chip output signal pad in series with its respective input signal pad on the bottom chip.
• the one or more input signal pads, the one or more common connection signal pads and the one or more output signal pads can be disposed along a single edge of the top chip.
• the one or more input signal pads can be disposed on the same side of the center line of the top chip.
• the device can further include a plurality of serial connection through-chip vias connecting top chip output signal pads in series with their respective input signal pads on the bottom chip and/or a plurality of parallel connection through-chip vias connecting top chip common connection signal pads in parallel with their duplicate common connection signal pads on the bottom chip.
• the stacked chips are aligned so there is substantially no offset.
• an edge of a top chip can line up vertically with a corresponding edge of the bottom chip.
• the stacked chips face the same direction as one another.
• a side of the first chip having selected signal pads can face the same direction as a side of the second chip having the same selected signal pads.
• the present invention provides a multi-chip device comprising a plurality of substantially identical chips including a top chip, an even number of intermediate chips and a bottom chip.
• Each chip includes one or more input signal pads and one or more common connection signal pads.
• Each common connection signal pad is symmetrically disposed on or about a center line of the chip with respect to a duplicate common connection signal pad.
• One or more output signal pads are symmetrically disposed about the center line of the chip with respect to respective input signal pads.
• a parallel connection through-chip via connects corresponding common connection signal pads on each chip together in parallel.
• a serial connection through-chip via connects an output signal pad on one chip in series with its respective input signal pad on another chip.
• the top chip has the one or more input signal pads for connection to external input signals, the common connection signal pads for connection to external common signals, and the one or more output signal pads connected to respective input signal pads of an adjacent chip.
• the bottom chip has the one or more output signal pads for connection to external output signals, the common connection signal pads for connection to the external common signals and the one or more input signal pads connected to respective output signal pads of an adjacent chip.
• At least one of the intermediate chips has the one or more output signal pads connected serially to respective one or more input signal pads of an adjacent intermediate chip.
• the plurality of substantially identical chips have substantially identical signal pad arrangements and are provided in a stack. Each alternating chip in the stack is flipped in orientation with respect an adjacent chip.
• the even number of intermediate chips can be an even multiplicity of intermediate chips having the one or more output signal pads connected to respective one or more input signal pads of a plurality of adjacent intermediate chips.
• the device can further include an insulator disposed between pads of adjacent intermediate chips to prevent contact between selected adjacent pads.
• the parallel connection through-chip via can extend through the insulator and through the corresponding common connection signal pads of the intermediate chips.
• a through-pad via can extend through the insulator to connect the one or more output signal pads of one of the intermediate chips to respective one or more input signal pads of an adjacent intermediate chip.
• the device can further include a controller for controlling access to the plurality of substantially identical chips.
• controller input connections can be provided to connect output signal pads from the bottom chip to an input side of the controller.
• Controller output connections can be provided to connect an output side of the controller to the input pads of the top chip.
• the controller can placed below the stacked chips, in which case the controller output connections can comprise wire bonding, or can be placed above the stacked chips, in which case the controller input connections can comprise wire bonding.
• the present invention provides a method for stacking serially-connected integrated circuits including the following steps: flipping a first chip so that its top side bearing transistors faces in a first direction to become a bottom chip; placing a second chip on top of the flipped first chip, the second chip being substantially identical in pad arrangement and placement to the first chip; creating through pad and chip via holes to facilitate connection of signal pads of the top chip to corresponding signal pads of the bottom chip to create at least one series connection and at least one parallel connection; disposing an insulation layer in the via holes; and disposing a conductor in the via holes to create through-via connections between the pads on the top chip and the bottom chip to create a stacked pair of integrated circuit chips.
• the step of creating the through pad and chip via holes can include creating a first through-chip and through-pad via hole to facilitate connection between a top chip common connection signal pad in parallel with its duplicate common connection signal pad.
• the step of creating the through pad and chip via holes can include creating a second through-chip and through-pad via hole to facilitate connection between a top chip output signal pad in series with its respective input signal pad on the bottom chip.
• the method can further include the following steps: depositing an insulation layer on top of the stacked pair of integrated circuit chips; forming contact holes in the insulation layer to permit connection between certain adjacent signal pads when another chip is later placed on top; depositing a conductor into the contact holes; etching a conductor layer to remove excess conductor material from the portions outside the contact holes; and attaching two previously combined chips on top of the stacked pair of integrated circuit chips to create a multi-chip circuit for a multi-chip package, the two previously combined chips being substantially identical to the stacked pair of integrated circuit chips.
• the method can still further include the following steps: providing a memory controller for controlling access to the plurality of substantially identical chips; connecting input signal pads of the top chip to an output side of the controller; and connecting output signal pads from the bottom chip to an input side of the controller.
• the present invention provides a multi-chip device comprising a plurality of substantially identical chips including a top chip and a bottom chip.
• the top and bottom chips have substantially identical signal pad arrangements, the bottom chip being flipped in orientation with respect to the top chip.
• the device includes at least one serial through-chip via to connect at least one output signal pad of the top chip to a respective input signal pad of the bottom chip.
• At least one parallel through-chip via is provided in the device to connect at least one common connection signal pad on the top chip to at least one duplicate common connection signal pad on the bottom chip.
• the present invention provides a multi-chip device comprising a plurality of substantially identical chips including a top chip, an even number of intermediate chips and a bottom chip. Each chip in the device has substantially identical signal pad arrangements. The chips are provided in a stack. Each alternating chip in the stack being flipped in orientation with respect an adjacent chip. The device further includes at least one parallel through-chip via, at least one serial through-chip via, and at least one serial connection between output and input signal pads of two of the intermediate chips.
• the present invention provides a multi-chip package comprising a plurality of substantially identical chips including a top chip, an even number of intermediate chips and a bottom chip.
• the chips are provided in a stack.
• Each chip in the device has substantially identical signal pad arrangements.
• Each alternating chip in the stack is flipped in orientation with respect an adjacent chip.
• the device also includes at least one parallel through-chip via, at least one serial through-chip via, and at least one serial connection between output and input signal pads of two of the intermediate chips.
• the device further includes package input connectors for connection to external input signals, and package output connectors for connection to external output signals.
• the present invention provides a method of fabricating a multi-chip device having two pairs of stacked chips, including the following steps: flipping a first chip so that its top side bearing transistors faces in a first direction to become a bottom chip; placing a second chip on top of the flipped first chip, the second chip being substantially identical in pad arrangement and placement to the first chip; creating through pad and chip via holes to facilitate connection of signal pads of the top chip to corresponding signal pads of the bottom chip to create at least one series connection and at least one parallel connection; disposing an insulation layer in the via holes; disposing a conductor in the via holes to create through-via connections between the pads on the top chip and the bottom chip to create a stacked pair of integrated circuit chips
• the method further includes: depositing an insulation layer on top of the stacked pair of integrated circuit chips; forming contact holes in the insulation layer to permit connection between certain adjacent signal pads when another chip is later placed on top; depositing a conductor into the contact holes; etching a conductor layer to remove excess conductor material from the portions outside the contact holes; attaching two previously combined chips on top of the stacked pair of integrated circuit chips to create a multi-chip circuit for a multi-chip package, the two previously combined chips being substantially identical to the stacked pair of integrated circuit chips; adding wire bonding to connect input signal pads of the top chip to an output side of the controller and to connect output signal pads from the bottom chip to an input side of the controller; and covering the entire package or compound.
• Fig. 1 shows a partial top view and cross-section view of a conventional multi-chip stack
• FIG. 2 is schematic drawing of an exemplary circuit suitable for fabrication in accordance with an embodiment of the present invention
• Figs. 3A-3C provide a partial top view, cross-section front view, and partial bottom view, respectively, of a simplified orthographic representation including an embodiment of the circuit shown in Fig. 2;
• Fig. 4 is another simplified partial top view of the embodiment of Fig. 3;
• Figs. 5A-5C provide a partial top view, cross-section front view, and partial bottom view, respectively of a simplified orthographic representation including another embodiment of the circuit shown in Fig. 2;
• Figs. 6A-6C provide a detailed partial top view, cross-section front, and bottom view, respectively, of the embodiment of the circuit in Fig. 2;
• Figs. 7 and 8 show steps of a method of fabricating the embodiment shown in Fig. 6 in accordance with the present technique
• Fig. 9 is a front cross-section view of another multi-chip circuit in accordance with an embodiment of the present invention.
• Fig. 10 is a front cross-section view of a multi-chip package in accordance with another embodiment of the present invention.
• the present invention provides a multi-chip device and method of stacking a plurality of substantially identical chips to produce the device.
• the multi-chip device, or circuit includes at least one through-chip via providing a parallel connection between signal pads from at least two chips, and at least one through-chip via providing a serial or daisy chain connection between signal pads from at least two chips.
• Common connection signal pads are arranged symmetrically about a center line of the chip with respect to duplicate common signal pads.
• Input signal pads are symmetrically disposed about the center line of the chip with respect to corresponding output signal pads.
• the chips in the stack are alternating flipped versions of the substantially identical chip to provide for this arrangement.
• At least one serial connection is provided between signal pads of stacked and flipped chips when more than two chips are stacked.
• the short interconnect of through hole vias provides less inductance, capacitance, and resistance so that signal integrity of the MCP is better than if bonding wire had been used.
• the size of package can be minimized compared to an equivalent package using bonding wire.
• An embodiment of the present invention provides a method for stacking integrated circuits using through chip via holes instead of bonding wire.
• serially connected multiple components in a single package provide a different approach to connecting the output of a previous device to the input of a present device to make serial connection between output and input ports.
• An embodiment of the present invention provides a method for making serially connected multi-chip devices.
• the present technique provides a method to make short line connections using the through-silicon-via method.
• the term "serial connection" and variations thereof as used herein represent any connection facilitating a daisy chain or ring topology connection. In a ring topology of serially connected chips, the last chip can loop back to the controller.
• FIG. 2 there is shown schematically a circuit 200 including serially connected integrated circuits.
• This circuit 200 includes a four chip flash memory circuit and is used as an example for descriptive purposes.
• the present technique is also applicable to dynamic random access memory (DRAM), static random access memory (SRAM), application specific integrated circuit (ASIC), a central processing unit (CPU) or any other type of multi-chip circuit having a serial connection topology similar to that described herein below.
• DRAM dynamic random access memory
• SRAM static random access memory
• ASIC application specific integrated circuit
• CPU central processing unit
• any other type of multi-chip circuit having a serial connection topology similar to that described herein below.
• Each chip in the circuit 200 includes connect signals that can be classified as one of three connect signal types as follows:
• RST Common connected signals: RST , CE , VREF, and power supplies (VDD, VSS, etc.).
• Serial input signals c ⁇ / CK, D[0:3], CSI, and DSI.
• Serial output signals c ⁇ 0 / CKO, Q[0:3], CSO and DSO.
• some of the parallel, or common connected, signals can include clock, reset, and chip select.
• the signals shown in Fig. 2 are examples, and one of ordinary skill in the art will appreciate that other signals can be appropriately placed into one of these groups based on the properties and connection requirements of the signal.
• One embodiment of the present invention has a parallel connected clock.
• a serial connection is used for the clock.
• Power must be parallel.
• Input and output signals, or signal pads, can be daisy-chained for any type of RAM, any logic, or even a CPU according to an embodiment of the present invention.
• FIGs. 3A-3C there is shown a simplified orthographic representation 300 including a partial top view 302 (in Fig. 3A) a cross-section front view 304 (in Fig. 3B), and a partial bottom view 306 (in Fig. 3C) of an embodiment of the circuit 200 shown in Fig. 2.
• a partial top view 302 in Fig. 3A
• a cross-section front view 304 in Fig. 3B
• a partial bottom view 306 in Fig. 3C of an embodiment of the circuit 200 shown in Fig. 2.
• FIG. 3C For clarity, only a subset of the connect signals is shown. In this embodiment, two substantially identical chips are stacked and connected.
• Fig. 3B which is a cross-section taken along line A-A in Fig.
• the pair of stacked integrated circuit chips includes a top chip 308 and a bottom chip 310.
• the bottom chip 310 has a substantially identical signal pad arrangement as the top chip 308, and is flipped in orientation with respect to the top chip.
• each chip includes one or more input signal pads A3-A6 for connection to external input signals.
• One or more common connection signal pads A1-A2 are provided, with each common connection signal pad being symmetrically disposed about a center line 312 of the top chip with respect to a duplicate common signal pad B1-B2.
• One or more output signal pads B3-B6 are symmetrically disposed about the center line of the chip with respect to respective, or corresponding, input signal pads A3-A6.
• a parallel connection through-chip via 314 connects a top chip common connection signal pad in parallel with its duplicate common connection signal pad.
• a serial connection through-chip via 316 connects a top chip output signal pad in series with its respective, or corresponding, input signal pad on the bottom chip.
• FIGs. 3A-3C When the different views 302, 304 and 306 in Figs. 3A-3C are lined up together, they illustrate how the common connection pads on the top and bottom chips line up with one another when stacked, and how the input signal pads of the top chip line up with their corresponding output signal pads on the bottom chip. This is particularly evident when observing the pads from views 302 and 306 that are vertically aligned with one another.
• the arrangement of signal pads permits the use of through-chip vias for both parallel and serial, or daisy chain, connections in the same multi-chip package.
• the stacked chips are aligned so there is substantially no offset.
• an edge of a top chip lines up vertically with a corresponding edge of the bottom chip.
• all of the edges of a top chip can line up vertically with all of the corresponding edges of the bottom chip.
• the stacked chips face the same direction as one another.
• a side of the first chip having selected signal pads faces the same direction as a side of the second chip having the same selected signal pads.
• FIG. 4 illustrates another partial top view of the embodiment shown in Figs.
• Signal pads A3-A6 are mirror images of the signal pads B3-B6 about the center line 312 of the chip, and vice versa.
• the signal pads A3-A6 and B3-B6 can be serial input pads and serial output pads, respectively.
• Common connection pads A1 and A2 are duplicated and mirror images of their respective duplicates B1 and B2 about the center line of the chip.
• Signal pads A1 and B1 carry the same signal as each other, and signal pads A2 and B2 carry the same signal as each other.
• input pad A6 is provided at a distance L1 from the center line of the chip.
• Input pad A5 is separated from input pad A4 by a distance La.
• Figs. 5A-5C illustrate a simplified orthographic representation 500, including a partial top view 502 (in Fig. 5A), a cross-section front view 504 (in Fig. 5B), and a partial bottom view (in Fig. 5C) of another embodiment of the circuit 200 shown in Fig. 2.
• this embodiment shows an even multiplicity of chips in the multi-chip circuit or package, such as a plurality of pairs of stacked chips. Each alternating chip in the stack is flipped in orientation with respect an adjacent chip.
• the embodiment shown in Fig. 5B has a plurality of substantially identical chips including a top chip 508, a bottom chip 510, and an even number of intermediate chips.
• a first intermediate chip 512 and a second intermediate chip 514 there is a first intermediate chip 512 and a second intermediate chip 514.
• Each chip in the stack has substantially identical signal pad arrangements and has similar properties as the chips described in relation to Fig. 3.
• the multi-chip package has at least one parallel through-chip via, at least one serial through- chip via, and at least one serial connection between pads of stacked and flipped chips.
• the input signal pads A3-A6 and common connection signal pads A1-A2 and B1-B2 (shown in Fig. 5A) of the top chip 508 are for connection to external input signals and external common signals, respectively.
• One or more of the output signal pads of the top chip are connected to respective input signal pads of an adjacent chip, as will be described in further detail below.
• the output signal pads B3-B6 and common connection signal pads A1-A2 and B1-B2 of the bottom chip 510 are for connection to external output signals and external common signals, respectively.
• One or more of the input signal pads of the bottom chip are connected to respective output signal pads of an adjacent chip, as will be described in further detail below.
• At least one of the intermediate chips has one or more of its output signal pads connected to respective one or more input signal pads of an adjacent intermediate chip.
• an insulator 522 is provided to prevent a short between adjacent pads that are not supposed to make a contact with one another.
• the insulator can be disposed between pads of adjacent intermediate chips to prevent contact between selected adjacent pads, such as those between which a connection is not desired.
• Respective chip-to-chip common connections are made using co-linear through pad, chip, and insulator vias 518.
• the parallel connection through-chip via in this case extends through the insulator 522 and through the corresponding common connection signal pads of the intermediate chips.
• Respective serial connections between output ports and input ports are made using through chip vias 520 or through pad vias 524.
• a through-pad via 524 extends through the insulator to connect the one or more output signal pads of the intermediate chips to respective one or more input signal pads of adjacent chips.
• the serial connections can facilitate daisy chain or loop topology connections.
• the pads for the input and output can physically touch each other to make connections for "intermediate" chips in the stack.
• the input and output ports on the top and bottom chips in the stack are not connected to other pads, but to the appropriate external connections.
• the power connection will also come from external, and have a direct parallel connection through the stack using a through-chip via.
• the external connections to the common connections are shown on both the top and bottom chips of the stack.
• signals such as CE , RST , and VREF have a single top or bottom connection while power supplies such as VDD, VSS, VDDQ, and VSSQ have both top and bottom connections.
• the present invention provides a multi-chip device comprising a plurality of substantially identical chips.
• Each chip includes one or more common connect signal pads wherein each signal pad is symmetrically disposed on a center line of the chip or symmetrically disposed about the center line of the chip with respect to a duplicate common signal pad.
• One or more input signal pads are also provided in each chip, as well as one or more output signal pads.
• the output signal pads are symmetrically disposed about the center line of the chip with respect to the respective input signal pads.
• Each common connect signal pad on each chip is connected to respective common connect signal pads on the other chips by co-linear through chip vias.
• the plurality of substantially identical chips includes a top chip and a bottom chip.
• the top chip has the one or more input signal pads for connection to external input signals, the common connection signals for connection to external common signals, and the one or more output signal pads connected to respective input signal pads of an adjacent chip.
• the bottom chip has the one or more output signal pads for connection to external output signals, the common connection signals for connection to the external common signals and the one or more input signal pads connected to respective output signal pads of and adjacent chip.
• An even number of middle chips have the one or more output signal pads connected to respective one or more input signal pads of adjacent chips.
• Figs. 6A-6C illustrate a simplified orthographic representation 500, including a detailed partial top view 602 (in Fig. 6A), a cross-section front view 604 (in Fig. 6B), and a partial bottom view 606 (in Fig. 6C) of a multi-chip package 600, which is an embodiment of the circuit 200 shown in Fig. 2. All of the connect signals are shown.
• CE is symmetrically disposed on a center line of the chip, it is not duplicated.
• An exemplary serial or daisy chain connection between input pad CSI (Common Strobe Input) on the top chip and output port CSO (Common Strobe Output) on the bottom chip will be described. This provides further details on serial or daisy chain connections in a stack with four chips, or any higher even number of chips.
• an external connection carries the common strobe input signal into CSI pad 610 on the top chip.
• CSO pad 612 within the top chip carries the corresponding output signal.
• a through-chip via 614 takes the output from CSO pad 612 and connects it as the input to the CSI pad 616 of the first intermediate chip.
• CSO pad 618 within the first intermediate chip carries the output signal.
• the CSO pad 620 of the second intermediate chip is isolated from the CSI pad 614 of the first intermediate chip by the insulator 622 to prevent connection between those two adjacent pads in the stack.
• a through-pad via 624 takes the output from CSO pad 618 of the first intermediate chip and connects it as the input to the CSI pad 626 of the second intermediate chip.
• CSO pad 620 within second intermediate chip carries the corresponding output signal.
• a through-chip via 628 takes the output from CSO pad 620 and connects it as the input to the CSI pad 630 of the bottom chip.
• CSO pad 632 in the bottom chip carries the output signal to an external connection.
• the common connection pads include one or more power pads, the number of which is sufficient to supply enough operation current and stable voltage level when simultaneous input and output buffers are executed.
• Figs. 7 and 8 show steps in a method of fabricating a multi-chip device according to an embodiment of the present invention.
• the top sides of each chip which is a surface formed with transistors, face opposite each other and the two pads are vertically connected to each other with a through-chip via, such as a through-silicon via.
• a through-chip via such as a through-silicon via.
• an insulation layer is deposited to prevent any electrical shorts between pads of two combined multi-chips (total of 4 chips).
• Fig. 7 illustrates steps for fabricating a stacked pair of integrated circuit chips
• Fig. 8 illustrates further steps in fabricating a multi-chip device having a plurality of pairs of stacked chips, or pairs of combined chips.
• step 702 shows that a first chip is flipped so that its top side bearing transistors faces in a first direction, such as down, to become a bottom chip.
• step 704 a second chip is placed on top of the flipped first chip, the second chip being substantially identical in pad arrangement and placement to the first chip.
• step 706 through pad and chip via holes are created to facilitate connection of signal pads of the top chip to corresponding signal pads of the bottom chip to create at least one series connection and at least one parallel connection.
• step 706 can include creating a first through-chip and through-pad via hole to facilitate connection between a top chip common connection signal pad in parallel with its duplicate common connection signal pad.
• Step 706 can further include creating a second through-chip and through-pad via hole to facilitate connection between a top chip output signal pad in series with its respective input signal pad on the bottom chip.
• step 708 an insulation layer is disposed in the via holes.
• a conductor e.g. copper
• step 710 a conductor (e.g. copper) is disposed in the via holes to create the through-via connections between the pads on the top chip and the bottom chip.
• a pair of stacked chips has been fabricated, the stack including at least one parallel connection through-chip via connecting a top chip common connection signal pad in parallel with its duplicate common connection signal pad, and at least one serial connection through-chip via connecting a top chip output signal pad in series with its respective input signal pad on the bottom chip.
• step 802 an insulation layer is deposited on top of the first stacked pair of integrated circuit chips.
• step 804 contact holes are formed in the insulation layer to permit connection between certain adjacent signal pads when another chip is later placed on top.
• step 806 a conductor is filled, or deposited, into the contact holes formed in the previous step.
• step 808 a conductor layer is etched so that excess conductor material is removed from the portions outside the contact holes.
• step 810 two previously combined chips, fabricated in accordance with the steps 702-710 in Fig. 7, are attached on top of the first stacked pair of integrated circuit chips to create a multi-chip circuit for a multi-chip package.
• a method for stacking serially-connected integrated circuits comprises the following steps: flipping a first chip; placing second chip on first chip; making through pad and chip via holes on common connections and output port of the second chip; disposing an insulation layer in the via holes; disposing a conductor in the via holes (ex. copper); depositing an insulation layer; forming contact holes in the insulating layer; filling conductor into the contact holes; etching a conductor layer; and attaching the two chips to previously combined chips.
• Fig. 9 is a front view of another circuit 900 in accordance with an embodiment of the present invention.
• the stack of identical chips has external connections either to a package input and output, or to pins or balls, such as a ball grid array (BGA).
• BGA ball grid array
• the circuit can get to the pin, or lead frame on the package, with more bonding wires or a ball grid.
• the BGA is well known in the memory industry for providing high performance, such as for CPU packages.
• the ball grid is the system bus and can be used with parallel or serial (daisy chain) connections.
• BGA provides less capacitance and loading compared to pin-based or TSOP (thin small-outline package) connections.
• DDR2 and DDR3 and other high speed devices use BGA.
• BGA is used for interfacing with the outside, and not for inter-chip connection.
• Fig. 10 illustrates a front cross-section view of a multi-chip package 1000 according to another embodiment of the present invention.
• a memory system having a plurality of cascaded memory devices is provided.
• the memory devices can be serially connected, and an external memory controller can receive and provide data and control signals to the memory system.
• an external memory controller can receive and provide data and control signals to the memory system.
• a similar arrangement is described in commonly assigned United States Patent Application Publication No. 2007/0076479-A1 entitled “Multiple Independent Serial Link Memory", published on April 5, 2007 and filed on December 30, 2005, which is incorporated herein by reference.
• a controller 1002 is placed below the stacked chips 1004. Output signal pads from the memory are connected by way of controller input connections 1006 to the input side of the controller.
• the controller input connections 1006 can be wire bonding, vias, a ball grid or any other suitable connection.
• the output side of the controller is connected by way of controller output connections 1008 to the input pads of the top chip of the memory stack.
• the controller output connections 1008 can be wire bonding or any other suitable connection. Only a few representative connections are shown in Fig. 10 to illustrate the type and nature of connection.
• the controller can be placed on top to connect the output side of the controller to the input side of the memory. Suitable controller output connections are provided to make those connections, and suitable controller input connections are provided to connect the output side of the memory stack to the input of the controller. In such an embodiment, a loop connection can be facilitated by the serial connections in the stack, where the last device loops back to the controller.
• the creation of through-chip vias as described in relation to Figs. 7 and 8 are some of the steps in the manufacturing process. Additional steps can be included when a controller is involved.
• controller input and output connections are added. This can comprise adding wire bonding to connect the controller outputs to the memory inputs, or vice versa.
• a further step includes covering the entire package or compound.
• the chips illustrated in Figs. 3 to 10 are fabricated using silicon substrate technology. However, embodiments fabricated using gallium-arsenide, germanium, silicon-germanium or any other substrate technologies are within the present technique.
• pads are disposed along a single edge of the chip in the embodiments shown in Figs. 3 to 10 for clarity and ease of illustration.
• the pads may be disposed along two, three, or four edges of the chip and still be within the present technique.

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• 2008
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