Method for stacking serially-connected integrated circuits and multi-chip device made from same
View Patent ↗A multi-chip device and method of stacking a plurality substantially identical chips to produce the device are provided. 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.
1. A method for stacking serially-connected integrated circuits comprising:
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.
2. The method of claim 1 wherein the step of creating the through pad and chip via holes comprises 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.
3. The method of claim 1 wherein the step of creating the through pad and chip via holes comprises 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.
4. The method of claim 1 further comprising:
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.
5. The method of claim 4 further comprising:
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.
6. A method of fabricating a multi-chip device having two pairs of stacked chips, comprising:
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;
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; and
adding wire bonding to connect input signal pads of the top chip to an output side of a 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.