Breakdown Mechanisms and Lifetime Prediction for 90-nm-Node Low-Power HfSiON/SiO 2 CMOSFETs

The mechanisms of gate leakage current and that of time dependent dielectric breakdown (TDDB) failure of HfSiON/SiO 2 gate dielectrics having an equivalent oxide thickness of 1.6 nm were investigated. The leakage current mechanism was found to be different for low and high electric fields, which we attribute to the difference in barrier height between interfacial SiO 2 and HfSiON. The mechanism of TDDB also proved to be different for low and high electric fields. Accordingly, TDDB lifetime must be evaluated in the low-gate-bias region, where the leakage current mechanism is the same as that of the actual FET operating voltages. A system for detecting defect generation using an emission microscope was developed, enabling low-bias TDDB measurements of large-gate-area transistors. Through this investigation, it was predicted that HfSiON/SiO 2 has much more than 10 years' TDDB reliability.