Luis Miguel Procel

Origins and implications of increased channel hot carrier variability in nFinFETs

Channel hot carrier (CHC) stress is observed to result in higher variability of degradation in deeply-scaled nFinFETs than bias temperature instability (BTI) stress. Potential sources of this increased variation are discussed and the intrinsic time-dependent variability component is extracted using a novel methodology based on matched pairs. It is concluded that in deeply-scaled devices, CHC-induced time-dependent distributions will be bimodal, pertaining to bulk charging and to interface defect generation, respectively. The latter, high-impact mode will control circuit failure fractions at high percentiles.

Defect-Centric Distribution of Channel Hot Carrier Degradation in Nano-MOSFETs

The defect-centric distribution is used, for the first time, to study the channel hot carrier (CHC) degradation. This distribution has been recently proposed for bias temperature instability (BTI) shift and we show that it also successfully describes the CHC behavior. This distribution has the advantage of being described by two physics-based parameters, the average threshold voltage shift produced by a single charge η and the number of stress-induced charged traps Nt. We study the behavior of η and Nt on nFETs with different geometries for different CHC stress times. As in the case of BTI, we observe that: 1) during the CHC stress, η is constant and Nt increases at the same rate of ΔVth and 2) η scales as 1/Area. We show that the density of charged traps induced by CHC stress strongly increases with reducing channel length, in contrast to BTI, where the density of charged traps is independent of the device geometry. The defect analysis enabled by the defect-centric statistics can be used to deepen our understanding of CHC degradation in nanoscale MOSFETs, where the defects are reduced to a numerable level.

Hydrogen impurity in SrTiO3: structure, electronic properties and migration

The present paper reports a computational investigation of the geometry and electronic structure as well as the migration of a hydrogen impurity in the cubic SrTiO3 crystal. The study is done using an approach based on the Hartree–Fock theory and developed for periodic systems. It is found that the H impurity forms the so-called OH group at the equilibrium. Analysis of electron density within the defective region implies the enhancement in covalent chemical bonding. A possible defect migration has been also investigated.

Structural and electronic properties of PZT

The structural and electronic properties of Zr-doped PbTiO3 crystals are investigated. A quantum-chemical INDO method based on the Hartree-Fock theory is employed, along with a periodic large unit cell (LUC) model, as implemented into the computational program SYM-SYM. The most stable defect configurations found to be those that allow the maximum displacements of oxygen atoms -- and the atomic relaxation around the Zr impurity are described for different impurity concentrations. Results are compared with those from various theoretical and experimental studies.

Quantum-chemical study of excitons in tetragobnal BaTiO3 and SrTiO3 crystals

Using a quantum-chemical INDO method based on the Hartree-Fock formalism and the periodic large unit cell (LUC) model we present a theoretical interpretation of the structural and electronic properties of triplet excitons in the tetragonal BaTiO3 and SrTiO3 crystals. Our study demonstrates that the exciton structure has particularities in each material. In the BaTiO3 the defect structure corresponds to the so-called Mott-Wannier-type exciton having a considerable separation, 7.0 Å, between the hole and the electron. Meanwhile, in SrTiO3 the structural and electronic features of the triplet exciton are quite different. The hole-electron distance is about 2.14 Å and the defect is well localized in two contiguous atoms: the hole on one of the O atoms and the electron on the neighbor Ti atom. The calculated luminescence energy using the so-called ΔSCF method is found to be equal to 0.94 eV and 1.13 eV for BaTiO3 and SrTiO3, respectively. Since it falls within the infrared part of the spectrum, the experimentally detected green luminescence due to photo-excited states should be attributed to the singlet excitons.

Study of the scaling and the temperature for RERAM cells using the QPC model

This article describes the OXRAM cell operation for different areas and temperatures using the Quantum Point Contact (QPC) model. Based on the QPC model the RERAM cell is described by a potential barrier variation using 2 parameters. The systematic extraction of this parameter for experimental I-V curves leads to conclude that the OXRAM cell does not depend on the scaling area cell but the temperature seems to degrade the performance cell above all for RERAM cell with dimension under 100nm. Further the needed energy to form the cells is increasing with the area scaling.