Hot carrier reliability of HfSiON NMOSFETs with poly and TiN metal gate

High-k dielectrics have been proposed to replace SiO₂ to reduce gate leakage current. Among reliability concerns of the hafnium based metal oxides (Y.H. Kim et al., Tech. Dig. of IEDM, p. 861, 2002) hot carrier effects may represent one of the major limitations for the high-k gate dielectrics introduction (Q. Lu et al., IRPS, p.429, 2002; A. Kumar, VLSI, p. 152, 2003). However, most of the studies did not take into consideration that the hot carriers-induced degradation might be accompanied by the electron trapping in the bulk of the high-k film (C.D. Young et al., IRW, p. 28, 2003) due to the high density of structural defects in the high-k dielectrics (G. Bersuker et al., Materials Today, vol. 26, Jan. 2004). This bulk electron trapping, which is not observed in the case of SiO₂ dielectrics, can significantly affect transistor parameters and, therefore, complicates evaluation of hot carrier degradation properties of the high-k gate stacks. In this paper, we investigate test conditions for the hot carrier stress of the poly and TiN gate NMOSFETs with HfSiON gate dielectric that would more accurately address the above issues.