Model for Oxide Wearout Due to Charge Trapping

Scaling of MOS gate oxides below 200Å can result in wearout of intrinsic oxides. This paper presents studies of thin gate oxides which show that the time dependent nature of oxide breakdown is due to charge trapping induced by leakage current. Failure occurs when the trapped charge increases the internal electric field in the oxide to a critical value of 11.2 MV/cm needed for avalanche breakdown. By measuring trapping parameters such as trap centroids and generation/recombination rates versus stress fields, a mathematical model for time dependent oxide wearout has been developed.