A Framework for Understanding Radiation-Induced Interface States in SiO2 MOS Structures

An empirical model of radiation-induced interface states at the SiO2/Si interface in SiO2 MOS capacitors is developed. The formulation explicitly addresses the time-dependent two stage nature of the buildup process, and it gives the mathematical dependencies of the experimentally observed buildup on time, field, temperature, and dose. The model is applied to both wet and dry grown oxides. The implications of the empirical model for microscopic mechanisms involved in the buildup are discussed. In particular, it is argued that the experimental observations can best be understood in terms of a positive ion (probably H+) release in the SiO2 bulk and the subsequent transport of the liberated ions to the SiO2/Si interface (for positive gate bias). The induced interface states result from an interaction of the ions at the interface.