Structural and Electrical Properties of EOT HfO2 (<1 nm) Grown on InAs by Atomic Layer Deposition and Its Thermal Stability
2016-03-01T00:00:00Z (GMT)
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We report on changes in the structural,
interfacial, and electrical characteristics of sub-1 nm equivalent
oxide thickness (EOT) HfO2 grown on InAs by atomic layer
deposition. When the HfO2 film was deposited on an InAs
substrate at a temperature of 300 °C, the HfO2 was
in an amorphous phase with an sharp interface, an EOT of 0.9 nm, and
low preexisting interfacial defect states. During post deposition
annealing (PDA) at 600 °C, the HfO2 was transformed
from an amorphous to a single crystalline orthorhombic phase, which
minimizes the interfacial lattice mismatch below 0.8%. Accordingly,
the HfO2 dielectric after the PDA had a dielectric constant
of ∼24 because of the permittivity of the well-ordered orthorhombic
HfO2 structure. Moreover, border traps were reduced by
half than the as-grown sample due to a reduction in bulk defects in
HfO2 dielectric during the PDA. However, in terms of other
electrical properties, the characteristics of the PDA-treated sample
were degraded compared to the as-grown sample, with EOT values of
1.0 nm and larger interfacial defect states (Dit) above
1 × 1014 cm–2 eV–1. X-ray photoelectron spectroscopy data indicated that the diffusion
of In atoms from the InAs substrate into the HfO2 dielectric
during the PDA at 600 °C resulted in the development of substantial
midgap states.
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