3D circuit design method

1. A 3D circuit design method implemented by a processing device, the method comprising:

partitioning a 2D circuit representation into two or more tiers of a 3D circuit representation, wherein the 2D circuit representation defines a plurality of circuit elements and a plurality of interconnecting wires, each interconnecting wire representing an electrical connection between two or more circuit elements, wherein each interconnecting wire is weighted based on at least one of: its length; its propagation delay; and its priority level based on the extent to which it represents a critical transmission path, the 2D circuit representation initially forming a first tier of the 3D circuit representation, the partitioning comprising the steps of:

a) selecting a first wire, interconnecting at least first and second circuit elements in the first tier, the first wire being selected as the highest ranking wire among the interconnecting wires based on its weight;

b) moving one of the first and second circuit elements connected by the selected wire to a further tier of the 3D circuit representation and replacing the interconnecting wire with a connecting via between the first and further tiers; and

c) repeating steps a) and b) for one or more further highest ranked interconnecting wires of the first tier;

performing place and route on the 3D circuit representation to generate a 3D circuit design; and

fabricating an integrated circuit based on the 3D circuit design.

2. The method of claim 1 , wherein the first wire has a weight greater than a first threshold.

3. The method of claim 2 , wherein steps a) and b) are repeated until one or more of the following conditions have been met:

there are no more interconnecting wires in the first tier having a weight greater than the first threshold;

the connecting via count has reached or has exceeded a limit;

a certain area ratio between the first tier and one or more further tier has been achieved; and

a certain power ratio between the first tier and one or more further tier has been achieved.

4. The method of claim 1 , wherein selecting a first wire comprises ranking the interconnecting wires based on their weights.

5. The method of claim 1 , wherein the interconnecting wires are weighted based on their lengths and the wire lengths are estimated using a half-perimeter-wire-length model.

6. The method of claim 1 , further comprising:

d) identifying in the 3D circuit representation an interconnecting wire having a weight less than a second threshold and that has been replaced by a connecting via;

e) restoring the identified interconnecting wire by replacing the connecting via by an interconnecting wire between circuit elements in a same tier; and

f) repeating steps d) and e) until there are no connecting vias replacing interconnecting wires that have a weight of less than the second threshold.

7. The method of claim 1 , wherein each circuit element in the 2D circuit representation comprises an indication of at least one of: its surface area; and its power consumption; the method further comprising:

verifying whether one of: an area ratio limit; a power consumption ratio limit; and a connecting via count limit, has been exceeded in the 3D circuit representation, and if so restoring one or more interconnecting wires by replacing the connecting via by an interconnecting wire between circuit elements in a same tier.

8. The method of claim 1 , wherein the 2D circuit representation is a 2D netlist, and partitioning the 2D circuit representation comprises converting the 2D netlist into a hypergraph having vertices corresponding to the circuit elements of the 2D circuit representation, and edges corresponding to the interconnecting wires of the 2D circuit representation.

9. The method of claim 1 , wherein the circuit elements are standard cells selected from a standard cell library.

10. The method of claim 1 , wherein the circuit elements are semiconductor devices, at least one of the circuit elements being a transistor.

11. A non-transitory storage device storing a computer program that, when executed by a processing device, causes the method of claim 1 to be implemented.

12. A computing device comprising:

one or more memories storing instructions and a 2D circuit representation; and

a processing device adapted to:

generate, under control of said instructions, a 3D circuit representation by:

partitioning the 2D circuit representation into two or more tiers of the 3D circuit representation, wherein the 2D circuit representation defines a plurality of circuit elements and a plurality of interconnecting wires, each interconnecting wire representing an electrical connection between two or more circuit elements, wherein each interconnecting wire is weighted based on at least one of: its length; its propagation delay; and its priority level based on the extent to which it represents a critical transmission path, the 2D circuit representation initially forming a first tier of the 3D circuit representation, the partitioning comprising the steps of:

a) selecting a first wire, interconnecting at least first and second circuit elements in the first tier, the first wire being the highest ranking wire among the interconnecting wires based on its weight;

b) moving one of the first and second circuit elements connected by the selected wire to a further tier of the 3D circuit representation and replacing the interconnecting wire with a connecting via between the first and further tiers; and

c) repeating steps a) and b) for one or more further interconnecting wires of the first tier; and

perform place and route on the 3D circuit representation to generate a 3D circuit design; and

causing to be fabricated an integrated circuit based on the 3D circuit design.

13. The computing device of claim 12 , wherein the first wire further interconnects one or more further circuit elements to the first and second circuit elements, and step b) further comprises moving one or more of the further circuit elements to the further tier.