Abstract
The set of MOS structures formed on n-type Si substrate with (NAOS)-SiO2/HfO2 gate dielectric layers was prepared and annealed in N2 atmosphere at various temperatures to stabilize the structure and to decrease the interface states density. Two Acoustic DLTS techniques using both surface (SAW) and longitudinal (LAW) acoustic waves including acoustoelectric response signal versus gate voltage dependence (Uac-Ug characteristics) were used to characterize the interface states and the role of annealing treatment. The main interface deep centers with activation energies about 0.30 and 0.20 eV, typical for dangling bonds were observed as well as a particular influence of annealing treatment on the interface states. The obtained results are analyzed, discussed and mutually compared.
Highlights
High permittivity dielectrics are subject of great study in order to replace SiO2 as gate dielectric in metal-oxidesemiconductor field-effect (MOS-FET) transistors in the future scales of integration [1]
The MOS structure prepared on n-type Si substrate wafers with nitric acid oxidation of Si (NAOS)-SiO2/HfO2 gate dielectric layer was formed by 5nm HfO2 oxide deposited by atomic layer deposition on 0.6 nm NAOS-SiO2 oxide film prepared in ~100 % HNO3 vapor [16]
Uac-Ug curve very well coincides with real one and, secondly, that the density of interface states course corresponds to the presence of interface states with energies around ~ 0.2 – 0.3 eV detected by A-DLTS (Table 1)
Summary
High permittivity (high-κ) dielectrics are subject of great study in order to replace SiO2 as gate dielectric in metal-oxidesemiconductor field-effect (MOS-FET) transistors in the future scales of integration [1]. The longitudinal acoustic wave (LAW) technique uses an acoustoelectric response signal (ARS) observed at the interface of the semiconductor structure when a longitudinal acoustic wave propagates through the structure [7 and 8] Because both TAS and ARS are very sensitive to any changes in the space charge distribution in the interface region their time development after an injection pulse has been applied to the structure (A-DLTS) and their dependence on external voltage (Uac-Ug curves) can be used to study the interface states properties including their activation energy, cross-section and concentration and interface states distribution [8 - 10].
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