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 integrated circuits 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 structurally irregular and radiation sensitive shallow trench isolation (STI) oxides. A new approach whereby non-uniform defect distributions along the STI sidewall are calculated, integrated into implicit surface potential equations, and ultimately used to model radiation-induced ldquoedgerdquo leakage currents in n-channel MOSFETs is described. The results of the modeling approach are compared to experimental data obtained on 130 nm and 90 nm devices. 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.