Band Edge Traps at Spectroscopically-Detected O-Atom Vacancies in Nanocrystalline ZrO2 and HfO2: An Engineering Solution for Elimination of O-Atom Vacancy Defects in Non-crystalline Ternary Silicate Alloys

Abstract

Spectroscopic studies, supported by theory indicate that neutral and negatively charged O-atom vacancies are the most important intrinsic defects in nanocrystalline thin films of Hf (Zr)O2. O-atom vacancy defects are identified in this paper by different spectroscopic technique: vacuum ultra-violet spectroscopic ellipsometry, near edge x-ray absorption spectroscopy, and cathodo-luminescence spectroscopy. O-vacancy defects are active as i) interface traps for Si substrate injection of holes, and ii) bulk film traps for Si substrate injection of electrons. The markedly different electron and hole trapping properties are a potentially serious problem for threshold voltage control and stability in CMOS inverter FETs using nanocrystalline Hf(Zr)O2 dielectrics. O-vacancy defects are not observed specrtroscopically in thermally and chemically stable Zr Si oxynitride alloy films, (SiO2)x(Si3N4)y(ZrO2)z, that have been annealed at 1100ºC in Ar. Si3N4 concentrations in these alloys must be controlled within narrow limits, ~0.36 to 0.4, with equal SiO2 and ZrO2 concentrations of approximately 0.32 to 0.3.