Olivier Nier

Quantum calculations of the carrier mobility: Methodology, Matthiessen's rule, and comparison with semi-classical approaches

We discuss carrier mobilities in the quantum Non-Equilibrium Greens Functions (NEGF) framework. We introduce a method for the extraction of the mobility that is free from contact resistance contamination and with minimal needs for ensemble averages. We focus on silicon thin films as an illustration, although the method can be applied to various materials such as semiconductor nanowires or carbon nanostructures. We then introduce a new paradigm for the definition of the partial mobility μM associated with a given elastic scattering mechanism “M,” taking phonons (PH) as a reference (μM−1=μPH+M−1−μPH−1). We argue that this definition makes better sense in a quantum transport framework as it is free from long range interference effects that can appear in purely ballistic calculations. As a matter of fact, these mobilities satisfy Matthiessens rule for three mechanisms [e.g., surface roughness (SR), remote Coulomb scattering (RCS) and phonons] much better than the usual, single mechanism calculations. We als...

Strain and layout management in dual channel (sSOI substrate, SiGe channel) planar FDSOI MOSFETs

We fabricated Fully-Depleted (FD) nMOSFETs on strain-SOI substrates (sSOI), exceeding regular FDSOI devices by +20% in nMOS ON-state current (ION) and +18% in SRAM read current. For pMOSFETs on sSOI, the integration of Si0.57Ge0.43 by the Ge-enrichment technique (in so-called sSGOI) is the solution to reach the performance of Si0.78Ge0.22 channels built on SOI (SGOI) in terms of short channel hole mobility and ION. We analyse the layout effects in sSOI/sSGOI transistors, ring oscillators (ROs) and SRAMs for different Ge amounts and strains and report for the first time the carrier mobility in sSOI/sSGOI vs. the active length (Lac). Through a layout optimization, a high uniaxial strain can be created, boosting the carrier mobility in both sSOI/sSGOI by 10/20% and ensuring the scalability of the planar FDSOI architecture for the 10nm node.

Quantum Modeling of the Carrier Mobility in FDSOI Devices

We compute the electron and hole mobilities in ultrathin body and buried oxide, fully depleted silicon on insulator devices with various high-\(\kappa \) metal gate-stacks using nonequilibrium Greens functions (NEGF). We compare our results with experimental data at different back gate biases and temperatures. That way, we are able to deembed the different contributions to the carrier mobility in the films (phonons, front and back interface roughness, and remote Coulomb scattering). We discuss the role played by each mechanism in the front and back interface inversion regimes. We draw attention, in particular, to the clear enhancement of electron- and hole-phonons interactions in the films. These results show that FDSOI devices are a foremost tool to sort out the different scattering mechanisms in Si devices, and that NEGF can provide valuable inputs to technology computer aided design.

Mobility in high-K metal gate UTBB-FDSOI devices: From NEGF to TCAD perspectives

This paper aims to review important theoretical and experimental aspects of both electrostatics and channel mobility in High-K Metal Gate UTBB-FDSOI MOSFETs. A simulation chain, including advanced quantum solvers, and semi-empirical Technology Computer Assisted Design (TCAD) tools is presented.

Modeling study of the mobility in FDSOI devices with a focus on near-spacer-region

We have studied the mobility in the FDSOI devices as a function of silicon thickness, doping, surface orientation and applying different back biases. This study is also done in the near-spacer-region that is partially inverted. Simulations have been obtained with a self-consistent Poisson-Schrödinger which provides a precise energy distribution of carriers and, allied to a Kubo-Greenwood carrier mobility solver, performs a quantum corrected drift diffusion (QCDD) model, capable of capturing non local effects on transport (tunneling) and mobility (influence of geometry).

Limits and improvements of TCAD piezoresistive models in FDSOI transistors

The usefulness for technology computer-aided design (TCAD) tools of the bulk linear piezoresistive theory is limited for two reasons. The first is that the normal effective field breaks piezoresistive tensor symmetries increasing the number of independent coefficients from three to six. The second reason is due to the non-linear behavior of the mobility change at high stress values. In this paper, we investigated the six-order polynomial piezoresistive model recently published by Synopsys (MCmob) [16,17]. We demonstrated that a 3D k-space Monte-Carlo solver cannot be used for MCmob parameters calibration (as initially proposed in [16]) as it does not account for quantum confinement. Instead, using self-consistent k.p Poisson-Schrodinger solvers (Kubo-2Dk Greenwood formalism [14, 15] for mobility), we determined a set of parameters for MCmob in the case of p-type FDSOI MOSFETs with <;100> and <;110>-oriented silicon channels on (100)-oriented wafers.

TCAD modeling challenges for 14nm FullyDepleted SOI technology performance assessment

This paper reviews the main challenges for the TCAD of 14nm Fully-Depleted Silicon-On-Insulator (FDSOI) technology performance assessment. Thanks to a multi-scale approach combining extensive electrical characterization and advanced solvers simulations, ensuring deep physical insight, we provide TCAD simulation framework for device layout optimization, strain engineering and device reliability assessment.

Effective field and universal mobility in high-k metal gate UTBB-FDSOI devices

This paper aims at reviewing experimental and theoretical behaviors of universal mobility in high-k metal gate UTBB-FDSOI devices. Based on split-CV mobility measurements, the parameter η characterizing the effective field, has been extracted for a large range of back voltages and temperatures in devices with various equivalent oxide thicknesses. We demonstrated that a nearly universal trend for the mobility with respect to the effective field can be obtained in the front inversion regime but is difficult to obtain in the back channel inversion regime.