The thermal stability of Dy Ox HfSiON and Ho Ox HfSiON gate dielectric stacks on silicon was studied by scanning transmission electron microscopy techniques and correlated with their electrical characteristics. Intermixing of the rare-earth elements with the HfSiON was observed, but there was no diffusion into the interfacial Si O2. Rapid thermal annealing (1000 °C) produced little detectable change in the concentration profile of the rare-earth elements but caused thinning of the interfacial Si O2 layer along with a corresponding increase in the rare-earth oxide layer thickness. These reactions could be explained with oxygen deficiency in the rare-earth oxide layer and its greater thermodynamic stability relative to Si O2. Negative flat band voltage shifts were observed relative to a control sample with no Dy Ox or Ho Ox. Mechanisms by which the observed microstructure changes could give rise to negative flatband voltage shifts are discussed.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)