Effects of Remote Plasma Pre-oxidation of Si Substrates on the Characteristics of ALD-Deposited HfO[sub 2] Gate Dielectrics (original) (raw)
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SiO 2 Free HfO 2 Gate Dielectrics by Physical Vapor Deposition
— HfO 2 layers, 25-Å thick, were grown by cyclic Hf sputter deposition and room temperature oxidation steps on chemically oxidized Si(001). Subsequent in situ annealing and TiN deposition yield a high-κ gate-stack for which the original 8-Å-thick SiO 2 layer is eliminated, as confirmed by transmission electron microscopy. Transistors fabricated with this gate-stack achieve an equivalent oxide thickness in inversion T inv = 9.7 Å, with a gate leakage J g = 0.8 A/cm 2. Devices fabricated without in situ annealing of the HfO 2 layer yield a T inv which increases from 10.8 to 11.2 Å as the oxidation time during each HfO 2 growth cycle increases from 10 to 120 s, also causing a decrease in J g from 0.95 to 0.60 A/cm 2 , and an increase in the transistor threshold voltage from 272 to 294 mV. The annealing step reduces T inv by 1.5 Å (10%) but also increases the gate leakage by 0.1 A/cm 2 (30%), and causes a 61 mV reduction in V t. These effects are primarily attributed to the oxygen-deficiency of the as-deposited HfO 2 , which facilitates both the reduction of an interfacial SiO 2 layer and a partial phase transition to a high-κ cubic or tetragonal HfO 2 phase. Index Terms— HfO 2 , high-k dielectrics, interface scavenging, MOSFET, physical vapor deposition (PVD), SiO 2 interlayer.
Applied Physics Letters, 2010
Er−doped HfO 2 ͑Erϳ 15%͒ films are grown by atomic layer deposition on Si͑100͒. The characteristics of the doped oxide are compared with those of HfO 2 . In Er−doped HfO 2 , the stabilization of the cubic structure, together with the effect of the high polarizability of Er 3+ , allow to obtain a dielectric constant of ϳ33 after annealing at 900°C. The insertion of Er within the metallic sublattice of HfO 2 reduces the net density of fixed charges, due to the creation of oxygen vacancies. For similar equivalent oxide thickness, lower leakage currents are measured for Er−doped HfO 2 than for HfO 2 .
Low-temperature growth of HfO2 dielectric layers by Plasma-Enhanced CVD
MRS Proceedings, 2003
HfO 2 dielectric layers have been grown on p-type Si(100) by plasma enhanced chemical vapor deposition (PE-CVD), using Ar-O 2 plasmas and hafnium(IV) tetra-t-butoxide as precursors. In-situ control of the plasma phase is carried out by optical emission spectroscopy (OES) and quadrupolar mass spectrometry (QMS). Structural and optical properties of the HfO 2 layers and of the HfO 2 /Si interface are investigated by spectroscopic ellipsometry (SE) in the photon energy range 1.5 -6.0 eV.. SE data are corroborated by results obtained from glancing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS).
Enhancement of Dielectric Properties of Nanoscale HfO2 Thin Films Via Atomic Layer Bombardment
ACS Applied Electronic Materials, 2020
The impacts of the atomic layer bombardment (ALB), which is the in-situ layerby-layer inert gas plasma treatment introduced in each atomic layer deposition (ALD) cycle, is explored to enhance the dielectric characteristics of nanoscale HfO2 thin films. Different ion bombardment modes, including the bombardment after precursor (BAP) and the bombardment after oxidant (BAO), were examined in detail to understand the ALB behaviors. In contrast with the detrimental effects caused by the BAP process, the BAO treatment contributes to a ~3-order-of-magnitude reduction of the leakage current density (Jg) and a ∼26% increase of the dielectric constant (K). The suppression of Jg and the enhancement of K can be attributed to the densification of thin film caused by the BAO process, as revealed by X-ray reflectivity characterizations. As a result, a low equivalent oxide thickness (~1.1 nm) and a low Jg (6.77×10-4 A/cm 2) are demonstrated in an ultrathin (~3 nm) HfO2 high-K gate dielectric prepared by the BAO ALD process. Hence the ALB treatment is demonstrated as a promising technique to significantly improve the dielectric characteristics of nanoscale thin films, which is critical in semiconductor, energy, and biocompatible applications.
Journal of Applied Physics, 2008
High dielectric constant hafnium oxide films were formed by electron beam ͑e-beam͒ evaporation on HF last terminated silicon ͑100͒ wafers. We report on the influence of low energy argon plasma ͑ϳ70 eV͒ and oxygen flow rate on the electrical, chemical, and structural properties of metal-insulator-silicon structures incorporating these e-beam deposited HfO 2 films. The use of the film-densifying low energy argon plasma during the deposition results in an increase in the equivalent oxide thickness ͑EOT͒ values. We employ high resolution transmission electron microscopy ͑HRTEM͒, x-ray photoelectron spectroscopy ͑XPS͒, and medium energy ion scattering experiments to investigate and understand the mechanisms leading to the EOT increase. We demonstrate very good agreement between the interfacial silicon oxide thicknesses derived independently from XPS and HRTEM measurements. We find that the e-beam evaporation technique enabled us to control the SiO x interfacial layer thickness down to ϳ6 Å. Very low leakage current density ͑Ͻ10 −4 A / cm 2 ͒ is measured at flatband voltage +1 V into accumulation for an estimated EOT of 10.9Ϯ 0.1 Å. Based on a combined HRTEM and capacitance-voltage ͑CV͒ analysis, employing a quantum-mechanical CV fitting procedure, we determine the dielectric constant ͑k͒ of HfO 2 films, and associated interfacial SiO x layers, formed under various processing conditions. The k values are found to be 21.2 for HfO 2 and 6.3 for the thinnest ͑ϳ6 Å͒ SiO x interfacial layer. The cross-wafer variations in the physical and electrical properties of the HfO 2 films are presented.