Papers by Keyword: Atomic Layer Deposition ALD

Abstract: High-k gate materials, such as HfO2, are unstable on silicon and form low permittivity interfacial oxides when heated. A single layer of silicon nitride grown prior to gate dielectric deposition could serve as a diffusion barrier to prevent oxide formation. A monolayer film of surface amine groups will be chemically similar to surface hydroxyl groups, and could also serve as a seed layer to promote the nucleation of a high-k film. The deposition of amines (≡Si-NH2 or ≡Si-NH-Si≡) on chlorine and hydrogen terminated Si(100) at low temperature (<100°C) was investigated using x-ray photoelectron spectroscopy (XPS). UV-Cl2 exposures (0.1-10 Torr Cl2 at 25-150°C, 10-600 s, 1000 W Xe lamp) were used to terminate Si(100) with Cl atoms. Exposure to NH3 (0.1-1000 Torr, 75°C, 5-60 min) replaced Cl atoms with up to 0.3 ML of amine groups, as measured by XPS. Cl atoms served as reactive leaving groups, lowering the overall activation energy barrier for nitridation. Alternatively, UV photons with energy greater than 5.7 eV were used to photodissociate NH3 molecules, yielding NH2 photofragments that reacted with the H-terminated Si(100) surface. At a UV photon flux of 19 mW/cm2, the N coverage increased with time and saturated at ~1 ML. Significant oxygen was observed on the surface due to H2O contamination in the source gas.

Abstract: Novel fabrication routes of oxide/semiconducting hybrid nanotubes or coaxial nanocables with 30~200 nanometers of radius and ~10 micrometers of length using atomic layer deposition (ALD) and soluble nano-templates was reported. In order to fabricate the hybrid nanotubes using nanotemplates, which were treated with surface modification using SAMs in order to achieve selective deposition only onto inner wall of the template. Deposition of metal oxide layers (TiO2, ZrO2) conformally and uniformly onto the wall of templates using ALD. To fabricate metal oxide/CdS nanocables or coaxial nanotubes, CdS was deposited onto metal oxide nanotubes by chemical bath deposition. Coaxial nanocables was also 30-200 nm in diameter and 1-10
in lengths.

Abstract: ZrO₂/Al₂O₃ bilayer structure was investigated as one of potential replacements for SiO₂ gate dielectric. Al₂O₃ and ZrO₂ films were also examined and showed stoichiometric characteristics with negligible chlorine and carbon impurities. Al₂O₃ film exhibited an amorphous structure without interlayer formation while ZrO₂ film showed a randomly oriented polycrystalline structure with amorphous phase of interlayer. ZrO₂/Al₂O₃bilayer film exhibited no interfacial layer between Si substrate and Al₂O₃ layers. The flat band voltage and hysteresis of ZrO₂/Al₂O₃bilayer film were 0.8 V and 150 mV, respectively, with fully reversible hysteresis. The measured leakage current of ZrO₂/Al₂O₃bilayer film was 1.2E-6 A/cm2 with EOT value of 1.4 nm. ZrO2/Al2O3 bilayer film showed significantly enhanced gate oxide properties compared to those of the individual Al₂O₃ and ZrO₂ films.