Role of Postdeposition Annealing and Doping with Si and Al Impurities in the Formation of Hf_xSi_1–xO₂ at the SiO₂/FE:HfO₂ Interface in a Ferroelectric Field-Effect Transistor

Abstract

Characterization of the composition and extension of the SiO2/HfO2 interface in the model systems Si-sub./SiO2 (7.5 nm)/FE:HfO2 (9.5 nm)/TiN (9 nm) for standard impurity concentrations and annealing temperatures (Si 3.6%, 1000 °C; Al 5.5%, 850 °C) were carried out using X-ray photoelectron spectroscopy with high kinetic energies. In addition, the crystalline properties of HfO2 were characterized by transmission electron microscopy and grazing incidence X-ray diffraction depending on the type of impurity. Formation of Hf x Si1–x O2 at the SiO2/HfO2 interface was revealed, and the dependence of its thickness d silicate and stoichiometry X on the formation of the tetragonal phase P42/nmc of HfO2 was established. It is shown that doping with aluminum followed by annealing prevents the formation of a tetragonal phase and reduces both d silicate and X by about 20% (with respect to undoped HfO2 annealed at the same temperature), in contrast to doping with Si followed by annealing, which practically does not affect d silicate and X. The results obtained are important for the problem of imbalance in the voltage drop across the gate oxides stack in a ferroelectric field-effect transistor and improvement of its endurance and retention characteristics.

Effect of high temperature annealing on cryogenic transport properties of silicon MOSFETs with a thin SiO2/HfO2 stacked dielectric

“…The annealing time directly affects the HfO 2 crystallization degree [31]. The annealing temperature affects the diffusion degree of the atoms [32] and oxygen vacancy content [33], which is related to the trapped charge [34]. Zhang et al found that with increasing annealing temperature, the interface charge increases at first and then decreases [35], while some other studies reported that the point defect and fixed charge decrease with the increasing annealing temperature [36].…”