1. A method of establishing a set of parameter values for use in simulating the operation of an integrated circuit, the integrated circuit being formed of a structure comprising a conductive layer formed upon a substrate and a plurality of interconnect layers formed over the conductive layer, and including inter-layer and intra-layer dielectrics and a dielectric layer over the topmost of the interconnect layers, the method including: for a first portion of the structure, characterized by a first subset of the parameters and including a first of said layers and a second layer adjacent to the first layer, optimizing the first portion of the structure to establish values for the first subset of the parameters; and for a second portion of the structure, characterized by a second subset of parameters and including the second of said layers and a third layer adjacent the second layer and distinct from the first, subsequently optimizing the second portion of the structure to establish values for the second subset, wherein the first and second subset share one or more of the parameters and the second subset is optimized holding the previously established values for the first subset fixed.