An improved fast hierarchical method (IFHM) for three-dimensional (3-D) capacitance extraction of IC Interconnects is presented.The fast hierarchical method (FHM) has been utilized for acceleration of the boundary element method (BEM) in solving the integral equations associated with the 3-D capacitance extraction problem.However

there is a shortcoming of the original FHM method: the criterion for hierarchical approximation is not explained and lack of theoretical support.The criterion plays a key role in the tradeoff between acceleration and precision.In the original FHM method the hierarchical approximation criterion was gained by a trial-and-error scheme.Here

specific and quantitative criterion is proposed in this improved FHM method.In addition

a new effective hierarchical scheme for charge evaluations is also proposed.The IFHM results in higher accuracy with about 1/3 computational time than the original FHM.Numerical examples are included to demonstrate the efficiency of this proposed IFHM.