H. Seo

Thermal evolution and electrical correlation of defect states in Hf-based high-κ dielectrics on n-type Ge (100): Local atomic bonding symmetry

The crystal field splittings and Jahn–Teller (J-T) distortions in Hf-based high-κ dielectric oxides on n-type Ge (100) substrates were investigated through the examination of Ou2009K1 edge spectra, obtained via x-ray absorption spectroscopy. Second derivative analysis of these Ou2009K1 edge spectra provided unambiguous evidence of J-T d-state degeneracy removal, resulting from the symmetry of the local atomic bonding environment. Additionally, two distinct defect states were found below the conduction band edge. The conduction band’s molecular orbital energy structure, including defect states, was determined based on the results of these investigations. Moreover, the thermal evolution of the defect states was found to be dependent on both postdeposition annealing temperature and Hf-based high-κ dielectric oxides. These subband-edge defect states were determined to be electrically active, and their density and the local atomic bonding symmetry were found to be correlated with the effective electron charge trapping...

Suppression of defect states in HfSiON gate dielectric films on n-type Ge(100) substrates

Defect states in HfO2 and HfSiON films deposited on Ge(100) substrates were studied by spectroscopic ellipsometry (SE) and x-ray absorption spectroscopy (XAS). In addition, structural and compositional changes in these films were examined via medium energy ion scattering (MEIS). SE and XAS experiments revealed two distinct band edge defect states, located at 1.7±0.1eV and at 2.7±0.1 below the conduction band edges of these films. The number of defect states in HfO2 increased noticeably following postdeposition annealing (PDA), whereas in HfSiON, it showed only small increases following the same treatment. MEIS measurements showed that Ge diffusion into HfO2 films was enhanced significantly by PDA as well; however, this effect was less pronounced in the HfSiON films. The suppression of defect state enhancement in HfSiON films was correlated with lower levels of Ge diffusion and increased structural stability with respect to HfO2.

Characterization of remote inductively coupled CH4-N2 plasma for carbon nitride thin-film deposition

We investigated reaction characteristics in a CH4∕N2 plasma for deposition of amorphous CNx thin films (a-CNx) by evaluating the change in electron density using the wave cutoff method, and the behavior of ions and radicals with an optical emission spectroscopy (OES). An inductively coupled plasma source that was 30cm away from the substrate stage was used for the discharge. The change in electron density in the substrate region and OES spectra in the plasma-source region were evaluated to investigate both the reaction mechanism and the remote effect while varying process conditions such as rf power, pressure, and gas-mixing ratio. We found that the electron density in the remote CH4∕N2 plasma was closely related to recombination reactions of major ions such as N2+, CH4+, CH3+, and H2+ during diffusion from the plasma source to the substrate. The electron density and optical emission of major ions and radicals in the CH4∕N2 plasma increase at higher rf power. The ratio [N]∕([N]+[C]) in a-CNx films, as mea...

Intrinsic bonding defects in transition metal elemental oxides

Gate dielectrics comprised of nanocrystalline HfO2 in gate stacks with thin SiO2/SiON interfacial transition regions display significant asymmetries with respect to trapping of Si substrate injected holes and electrons. Based on spectroscopic studies, and guided by ab initio theory, electron and hole traps in HfO2 and other transition metal elemental oxides are assigned to O-atom divacancies, clustered at internal grain boundaries. Three engineering solutions for defect reduction are identified: i) deposition of ultra-thin, < 2 nm, HfO2 dielectric layers, in which grain boundary formation is suppressed by effectively eliminating inter-primitive unit cell π-bonding interactions, ii) chemically phase separated high HfO2 silicates in which inter-primitive unit cell p-bonding interactions are suppressed by the two nanocrystalline grain size limitations resulting from SiO2 inclusions, and iii) non-crystalline Zr/Hf Si oxynitrides without grain boundary defects.

Surface characteristics of indium-tin oxide cleaned by remote plasma

We investigated the remote oxygen and hydrogen plasma cleaning of indium-tin oxide and its surface electronic properties. Samples cleaned by hydrogen plasma after oxygen plasma cleaning showed the complete absence of surface contaminants while samples cleaned by only hydrogen or oxygen plasma showed some residual contaminants. Work function is mainly affected by oxygen plasma treatments while sheet resistance is more closely related to the removal of surface carbon contaminants. This study revealed that surface dipoles due to the O- ions are believed to have a more significant contribution to the change in work function than the reduction of Sn4+.

Suppression of Ge–O and Ge–N bonding at Ge–HfO2 and Ge–TiO2 interfaces by deposition onto plasma-nitrided passivated Ge substrates: Integration issues Ge gate stacks into advanced devices

A study of changes in nano-scale morphology of thin films of nano-crystalline transition metal (TM) elemental oxides, HfO{sub 2} and TiO{sub 2}, on plasma-nitrided Ge(100) substrates, and Si(100) substrates with ultra-thin (-0.8 nm) plasma-nitrided Si suboxide, SiO{sub x}, x < 2, or SiON interfacial layers is presented. Near edge X-ray absorption spectroscopy (NEXAS) has been used to determine nano-scale morphology of these films by Jahn-Teller distortion removal of band edge d-state degeneracies. These results identify a new and novel application for NEXAS based on the resonant character of the respective O K{sub 1} and N K{sub 1} edge absorptions. This paper also includes a brief discussion of the integration issues for the introduction of this Ge breakthrough into advanced semiconductor circuits and systems. This includes a comparison of nano-crystalline and non-crystalline dielectrics, as well as issues relative to metal gates.

XAS Studies of Chemical Bonding of Nitrogen and Oxygen Atoms in Ti/Zr/Hf High‐K Gate Dielectrics

Near edge x‐ray absorption spectroscopy (NEXAS) has been used to study bonding in Ti/Zr/Hf (hereafter TM) Si oxynitrides and silicates. Comparisons between O K1 and N K1 spectra are particularly informative since O and N anti‐bonding molecular orbitals (MO) display distinct features from nearest‐ and next‐nearest‐neighbor TM and Si atoms. MO TM‐atom spectral features are qualitatively different in TM silicates and Si oxynitrides. NEXAS studies of TM silicates identity chemical phase separation (CPS) into TM‐dioxides and SiO2 for annealing to 900°C.

Spectroscopic detection of (i) intrinsic band edge defects, and (ii) transition metal (TM) and rare earth lanthanide (REL) atom occupied states in elemental and complex oxides: A novel pathway to (i) device reliability and (ii) increased functionality in ULSI CMOS

A novel application of synchrotron soft-X-ray spectroscopy is applied to (i) the detection of intrinsic bonding defects, and (ii) partially occupied TM and REL atom valence band edge dand d- and f-states. Spectroscopic identification and correlation with electrical performance is crucial for the identification and optimization of TM/REL elemental and complex oxides for advanced ULSI devices.

Spectroscopic Studies of Band Edge Electronic States in Elemental High‐k Oxide Dielectrics on Si and Ge Substrates

This paper uses X‐ray absorption spectroscopy, and vacuum ultra‐violet spectroscopic ellipsometry to distinguish between i) non‐crystallinity, and ii) nano‐crystallinity in transition metal (TM) elemental oxides. Near edge X‐ray absorption spectroscopy is used to distinguish between two different scales of nano‐crystalline order. The observation of band edge Jahn‐Teller splittings in anti‐bonding states with TM p‐character correlate with the observation of nano‐crystalline‐order that can be detected by X‐ray diffraction, and establish a length scale for order, λs>3 to 4 nm, The suppression of J‐T splittings, and a spectral broadening is associated with reduced nano‐crystalline order that can be detected by atomic‐scale imaging and/or extended X‐ray absorption spectroscopy for λs<∼2.5u2009nm. These different states of nano‐crystalline grain‐size order for addressed in elemental transition metal oxides on both Si and Ge substrates.