Yuuichi Kamimuta

Experimental evidence for the flatband voltage shift of high-k metal-oxide-semiconductor devices due to the dipole formation at the high-k∕SiO2 interface

We have examined an origin of the flatband voltage (VFB) shift in metal-oxide-semiconductor capacitors by employing bilayer high-k gate dielectrics consisting of HfO2 and Al2O3 on the interfacial SiO2 layer. We found that the high-k∕SiO2 interface affects the VFB shift through an electrical dipole layer formation at its interface, regardless of the gate electrode materials. Furthermore, we demonstrated that the VFB shift in the metal/high-k gate stack is determined only by the dipole at high-k∕SiO2 interface, while for the Si-based gate it is determined by both gate/high-k and high-k∕SiO2 interfaces.

Effects of nitrogen in HfSiON gate dielectric on the electrical and thermal characteristics

The effects of the nitrogen in the HfSiON gate dielectric on the electrical and thermal properties of the dielectric were investigated. It is clearly demonstrated that nitrogen enhances the dielectric constant of silicates. High dielectric constants of the HfSiON are maintained and boron penetration is substantially suppressed in the HfSiON during high temperature annealing. These properties are ascribed to the homogeneity of the bond structure in the film containing nitrogen through high temperature annealing.

Direct Comparison of ZrO2 and HfO2 on Ge Substrate in Terms of the Realization of Ultrathin High-κ Gate Stacks

Direct comparison of ZrO2 and HfO2 on Ge substrates was performed in terms of the realization of an ultrathin gate stack with low leakage current. Changes in the interfacial layer thickness, film dielectric constant and leakage current upon postdeposition annealing were investigated. Considerable thinning of the interfacial layer due to interdiffusion with ZrO2 was observed after annealing. Moreover, the high dielectric constant of ZrO2 was retained even after Ge incorporation by interdiffusion. These phenomena resulted in a small capacitance equivalent thickness (CET) of 1.2 nm. On the other hand, the interfacial layer under the high-permittivity (high-κ) film remained almost the same for HfO2 on Ge stack, resulting in a relatively large CET of 1.6 nm. Together with the fact that the leakage current is lower for the ZrO2 stack than that for the HfO2 stack, ZrO2 is considered to be preferable to HfO2.

Comprehensive Study of V FB Shift in High-k CMOS - Dipole Formation, Fermi-level Pinning and Oxygen Vacancy Effect

We have quantitatively investigated effective work function (Phi_m,eff) shift, and experimentally demonstrated that high-k/SiO₂ dipole and Si-based gate/high-k contribution are critically important for understanding anomalous V_FB shift. Furthermore, we have also found that annealing of metal/high-k gate stack in the reduction ambient induces another dipole formation at the high-k/Si02 interface. Finally, by using the AI₂O₃ and Y₂O₃ layer as a bottom high-k, the symmetric V_TH CMOS is successfully achieved with a single metal gate electrode.

Dielectric properties of noncrystalline HfSiON

The dielectric properties of noncrystalline hafnium silicon oxynitride (HfSiON) films with a variety of atomic compositions were investigated. The films were deposited by reactive sputtering of Hf and Si in an O, N, and Ar mixture ambient. The bonding states, band-gap energies, atomic compositions, and crystallinities were confirmed by X-ray photoelectron spectroscopy (XPS), reflection electron energy loss spectroscopy (REELS), Rutherford backscattering spectrometry (RBS), and X-ray diffractometry (XRD), respectively. The optical (high-frequency) dielectric constants were optically determined by the square of the reflective indexes measured by ellipsometry. The static dielectric constants were electrically estimated by the capacitance of Au/HfSiON/Si(100) structures. It was observed that low N incorporation in the films led to the formation of only Si-N bonds without Hf-N bonds. An abrupt decrease in band-gap energies was observed at atomic compositions corresponding to the boundary where Hf-N bonds start to form. By combining the data for the atomic concentrations and bonding states, we found that HfSiON can be regarded as a pseudo-quaternary alloy consisting of four insulating components: SiO

Determination of Band Alignment of Hafnium Silicon Oxynitride/Silicon (HfSiON/Si) Structures using Electron Spectroscopy

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Careful examination on the asymmetric Vfb shift problem for poly-Si/HfSiON gate stack and its solution by the Hf concentration control in the dielectric near the poly-Si interface with small EOT expense

, HfO

High-performance poly-Ge short-channel metal–oxide–semiconductor field-effect transistors formed on SiO2 layer by flash lamp annealing

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Re-examination of Flat-Band Voltage Shift for High-k MOS Devices

, Si

Dielectric Constant Behavior of Hf–O–N System

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