Characteristics of HfLaON/SiO2 Gate Stack Prepared Using Reactive Sputtering

HfLaON is one of the most promising high-k dielectrics because of its higher crystallization temperature and ability to tune the work function of the metal gates from Si midgap to around 4eV, meeting the requirement of nMOSFETs. In this paper, HfLaON was prepared using reactive sputtering that alternates between Hf and HfLa targets in N2/Ar ambient, followed by a post-deposition anneal. Before deposition of HfLaON film, SiO2 interfacial layer was grown to improve the interface properties. HfLaON/SiO2 gate stack exhibited good physical and electrical characteristics, including good thermal stability, excellent interface properties, small equivalent oxide thickness and low gate-leakage current. Further studies found that the excellent characteristics of the gate stack have close relation to the grown method of SiO2 interfacial layer. In order to investigate their relationship, the different grown methods of SiO2 interfacial layer were adopted and compared in the fabrication of HfLaON/SiO2 gate stacks, such as oxidation in O3/H2O solution, rapid thermal anneal in N2 or N2/O2 mixed gas.