HfO2 Dielectric Layer Research Articles

Temperature dependent defect formation and charging in hafnium oxides and silicates

We studied the thermal stability of hafnium oxides and silicates with femtosecond pump/probe photoelectron spectroscopy, employed to monitor photovoltage shifts in the underlying Si substrate induced by the absorption of femtosecond pulses of 800 nm light. Annealing of hafnium oxides and silicates, deposited on thin SiON interlayer oxides grown on lightly doped Si (100) substrates, reveals an abrupt onset of charging at elevated temperatures. Core level photoemission and transmission electron microscopy were used to correlate the observed charge injection at elevated temperatures with structural and chemical changes in the SiON and HfO2 dielectric layers.

Interface structure and non-stoichiometry in HfO2 dielectrics

High-resolution electron microscopy, electron energy-loss spectroscopy, and first-principles theory are used to investigate the composition and electronic structure of HfO2 dielectric layers deposited directly onto Si. A thin, nonstoichiometric, but Hf-free SiO2 layer forms between the HfO2 dielectric and the substrate, consistent with one-dimensional spinodal decomposition. Rapid thermal annealing crystallizes the HfO2, and the resulting grain boundaries within the HfO2 are found to be O-depleted, with localized states within the bandgap. These localized states are thought to act as significant leakage pathways, and may be responsible for Fermi-level pinning at the dielectric/contact interface.

Characteristics of HfO<sub>2</sub> Dielectric Layer Grown by MOMBE

The chemical and electrical characteristics of HfO2 dielectric layers grown on the p-type Si substrate by the metalorganic molecular beam epitaxy (MOMBE) technique were investigated. The XPS spectra showed that the Hf 4f and O 1s peaks shifted to the higher level of binding energy due to the charge 1transfer effect. Electrical properties were analyzed by C-V and I-V measurements. The distortion of C-V curve at depletion region is attributed to the effect of deep trap levels’ existence. Saturation capacitance and leakage current density were in the range of 207 ~ 249 pF and 0.52 ~ 0.58 A/cm2 respectively, and the flat band voltage shift to the higher voltage appeared as the oxygen flow rate increased.