A model for radiation induced edge leakage in bulk silicon NMOS transistors

A model for radiation-induced edge leakage in bulk silicon NMOS transistors is presented. The model is significant in two respects. First, it involves only the basic concepts of how fixed charge affects a MOS system. The excellent agreement with experimental data, therefore, implies that other factors not included in the model, such as stress, are less important. Second, it can be used to predict the response of various oxide isolation technologies as long as the oxide and substrate doping profiles are known. The model has been applied to devices with moat, LOCOS (local oxidation of silicon), and recessed field oxides. In all cases, the leakage current saturates only when the silicon immediately adjacent to the device window enters weak inversion. Since this region can be implanted directly for the moat process, it is more easily hardened to radiation. In contrast, the LOCOS and ROX (recessed oxidation) processes rely on side diffusion of the field implant to cut off the leakage under the encroaching bird´s beak