Simulation of SOI transistor circuits through non-equilibrium initial condition analysis (NEICA)

The simulation of circuits containing silicon-on-insulator (SOI) transistors encounters specific difficulties mainly due to the presence of the insulated body nodes, i.e., connected by high impedance connections with the rest of the circuit. These high impedance connections cause the charges stored in transistor body nodes to change at much slower rates than the normal operation of the circuit. Therefore the short term operation of a circuit will be strongly dependent on the state of the SOI transistor body charge, which in turn depends on the activity of the transistor during thousands of the previous cycles: the history effect. The presence of high impedance connections has another adverse effect on the simulation of such circuits: circuit matrices become severely ill-conditioned, thus slowing down or even compromising the convergence of the initial DC solution. In this paper, we are introducing the novel non-equilibrium, initial condition analysis (NEICA), as the preferred initialization method for circuits containing SOI devices. This method allows the user full control of the initial state of the SOI devices, preserves full insight into the physical phenomenon, and leads to a well-conditioned and thus reliable transient analysis initialization problem. The method is easily implemented in most existing circuit simulation programs and facilitates other important applications beyond the analysis of SOI transistor circuits. ESD analysis, and simulation of the effects of charged particles hitting circuits, are just two such examples