Interface States in Hf-Based Stacks and their Impact on the Reliability of these Alternative Oxides

Abstract

This paper investigates interface states in Hf-based devices with metal gate. By electrical measurements we first show that the interface defects of HfO2 stacks are very similar to those of conventional SiO2 oxides. To passivate these defects forming gas anneals FGA under N2/H2 can be performed at high temperature T>500{degree sign}C in Hf-based oxide. We also propose for the first time the use of an atomic H0 plasma performed at low temperature T~300{degree sign}C to passivate these interface defects. Finally we investigate the impact of the interface states on the reliability of High-K dielectrics. The interface state generation in HfO2 oxides annealed by FGA is similar to the one induced by NBTI stress in SiO2. On the other hand, in H0 annealed samples, degradation is enhanced due to plasma charging in the oxide. But some of the interface degradations induced by PID can be cured by standard thermal treatments.

Overview of Materials Processing and Properties of Lanthanum-Based High-k Dielectrics

“…Although a high-T RTA combined with high-T FGA processing is needed to obtain low levels of Q f and D it , there are potentially ways to lower the temperatures needed. These include: more aggressive in situ lanthanum silicate formation anneals; utilizing a higher %H 2 in the FGA; or using H-plasma passivation (27). Although it is recognized that a some intrinsic amount of interface states may be unavoidable due to bonding constraints at the silicate -silica interface (28), proper annealing and passivation may still reduce them to acceptable levels.…”