Total dose and bias temperature stress effects for HfSiON on Si MOS capacitors

We have performed an experimental study of the effects of ionizing radiation and bias-temperature stress on Si MOS devices with HfSiON gate dielectrics. We compare the responses of homogeneous high-Si3N4 films and loW-Si3N4 films that contain crystalline HfO2. We observe that the loW-Si3N4 films are more sensitive to ionizing radiation than the high-Si3N4 films. In particular, the loW-Si3N4 film that includes crystalline HfO2 is especially vulnerable to electron trapping due to substrate injection under positive irradiation bias. Both film types exhibit reduced radiation-induced charge trapping relative to previous Hf silicates. The high-Si3N4 film exhibits similar to 16x less radiation-induced net oxide-trap charge density than earlier Hf silicate films processed without nitride. We also find that these devices are relatively robust against bias-temperature stress instabilities. Consistent with the radiation response, the loW-Si3N4 devices also display elevated levels of charge trapping relative to the high-Si3N4 devices during bias-temperature stress.