Equivalent circuit modeling of guard ring structures for evaluation of substrate crosstalk isolation

A substrate-coupling equivalent circuit can be derived for an arbitrary guard ring test structure by way of F-matrix computation. The derived netlist represents a unified impedance network among multiple sites on a chip surface and allows circuit simulation for evaluation of isolation effects provided by guard rings. Geometry dependency of guard ring effects attributes to layout patterns of a test structure, including such as area of a guard ring as well as location distance from the circuit to be isolated by the guard ring. In addition, structural dependency arises from vertical impurity concentrations such as p⁺ , n⁺, and deep n-well, which are generally available in a deep-submicron CMOS technology. The proposed simulation based prototyping technique of guard ring structures can include all these dependences and thus can be strongly helpful to establish isolation strategy against substrate coupling in a given technology, in an early stage of SoC developments