Delay gate / interconnection

Figure 9.1 shows a graph relating gate delay to interconnection delay for a range of processes. 

Fig. 8 Gate and interconnect delay versus feature size. Interconnect delay is shown for repeater spacings of 3000 pm. (Some data adapted from Ref )...

Alpert CJ, Devgan A, Quay ST (1999) Buffer Insertion with Accurate Gate and Interconnect Delay Computation, DAC 1999, pp 479-484... 

Buffering has become indispensable in timing closure and cannot be ignored during interconnect delay estimation [11-13]. Therefore to calculate new locations of movable gates, one must adopt a buffering-aware interconnect delay model that accounts for future buffers. We found that the linear delay model described in [13, 14] is suited to physical synthesis applications. In this model, the delay along an optimally buffered interconnect is... 

Fig. 6.1 Example of interconnect-driven cloning. The arrival times of F and F2 are 0. The required arrival times of and S2 are 5. For simplicity, this example uses gate delays of 0. a Origintil circuit, b New circuit after cloning leaving buffering intact, c New circuit after cloning considering buffering...

On-chip interconnects present parasitic capacitance and resistance as loads to active circuits. Such parasitic loads had little impact on earlier ICs because the intrinsic gate delay dominated the total gate delay. 

For the design, a problem-oriented and abstract high-level design methodology and design description language should be used. There should be adequate testability (for production test). Gate and interconnection (wire) delays should be considered. 

Down to 1 jiim feature size, the delays in the circuit are primarily caused by the switching speed of the gate and the capacitance associated with the gates. However, as flie transistors shrink in size, their switching speed improves, but the resistance of the interconnect gets relatively worse. As feature sizes move towards 0.1 i, the majority of the delay in a system is due to interconnect delay. 

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