Modeling Ionizing Radiation Effects in Solid State Materials and CMOS Devices

A comprehensive model is presented which enables the effects of ionizing radiation on bulk CMOS devices and parasitic structures to be simulated with closed form functions. The model adapts general equations for defect formation in uniform SiO₂ films to facilitate analytical calculations of trapped charge and interface trap buildup in radiation sensitive shallow trench isolation (STI) oxides. An approach whereby defect distributions along the bottom and sidewall of the STI are calculated, incorporated into implicit surface potential equations, and ultimately used to model radiation-induced leakage currents in MOSFET structures and integrated circuits is described. The results of the modeling approach are compared to experimental data obtained on 130 and 90 nm devices and circuits. The features having the greatest impact on the increased radiation tolerance of advanced deep-submicron bulk CMOS technologies are also discussed. These features include increased doping levels along the STI sidewall.