Investigation of local charged defects within high-temperature annealed HfSiON/SiO2 gate stacks by scanning capacitance spectroscopy

We studied the oxide charges and traps within nitrided Hf-silicate (HfSiON)/SiO2 gate stacks processed with high-temperature annealing with a spectroscopic technique by using high spatial resolution scanning capacitance microscopy. Spectroscopy was performed by detecting the static capacitance (dC/dZ) between a conductive probe and the sample while sweeping the sample bias. The dC/dZ image and spatially resolved dC/dZ-V spectrum revealed the existence of positive fixed charges within HfSiON and interface trap charges between the SiO2 underlayer and Si substrate. We also observed a transient electron trap process from the conductive probe to the HfSiON film as abrupt discontinuities in the dC/dZ-V spectrum and with bias-induced topography change of the HfSiON surface. These oxide charges and trap sites distribute inhomogeneously within HfSiON/SiO2 gate stacks, and the origin of these charged defects is ascribable to phase separation induced by high-temperature postdeposition annealing. (c) 2007 American Institute of Physics.