An "effective" capacitance based delay metric for RC interconnect

Efficient, yet accurate delay estimation for RC interconnect is required for the optimization loop of timing driven physical design tools. For many applications, the Elmore delay metric has been widely used due to its efficiency and ease of use. However, it is well known that the Elmore metric can have significant error since it ignores the resistive shielding of downstream capacitance. We present a new interconnect metric called ECM that accounts for this resistive shielding by computing an effective capacitance to model the downstream capacitance. ECM can also be computed with the same complexity as the Elmore delay and does not require the computation of moment. Experiments show that ECM is significantly more accurate than Elmore delay and is competitive with other metrics that use multiple moments.