Highly Manufacturable and Reliable HfSiON N-FET With Poly-Si/a-Si Stacked Gate for LSTP Applications

We have proposed a novel poly-Si/a-Si/HfSiON transistor to enhance reliabilities without performance degradation for a 65-nm-node low standby power (LSTP) application. By insertion of a thin amorphous-Si layer between the Poly-Si gate electrode and HfSiON, both phosphorus penetration from gate electrode and a reaction at gate electrode/HfSiON interface are successfully suppressed, so that positive bias temperature instability, one of the biggest issues for high-k gate dielectric, is drastically improved by two orders of magnitude. By carefully optimizing the gate stack structure of HfSiON, the HfSiON device can satisfy both lower gate leakage and gate-induced drain leakage at the same time. As a result, an excellent I_on- I_standby (= I_g + l_off) characteristic can be achieved, compared to the conventional SiON device. The a-Si insertion technique can realize the combination between the high-k gate dielectric and Poly-Si for future LSTP applications.