Multi-scale strategy for high-k/metal-gate UTBB-FDSOI devices modeling with emphasis on back bias impact on mobility

Abstract

scale strategy for high-k/metal-gate UTBB-FDSOI devices modeling with emphasis on back bias impact on mobility. Journal of Computational Electronics, Springer Verlag, 2013, 12, pp.675-684. 10.1007 Multi-scale analysis of the mobility in high-k UTBB-FDSOI Devices and comparison to split-CV measurements. Abstract-A rigorous study of the mobility in high-k metal gate Ultra-Thin Body and Box Fully Depleted SOI (UTBB-FDSOI) devices is done by means of split C-V measurements and advanced simulations. Measurements have been performed for various Interfacial Layer (IL)Equivalent Oxide Thickness (EOT) allowing an investigation of the physical mechanisms responsible for the mobility degradation at high-k/IL interface. The impact of the back bias on transport properties is investigated and mobility enhancement in the forward regime (back gate inversion) is demonstrated. A multi-scale simulation approach is performed and we compared simulated mobility using quantum Non-Equilibrium Green's Functions (NEGF) to semi-classical solvers results using the Kubo Greenwood (KG) approach. We demonstrated good correlations between these solvers comparing phonon and remote Coulomb-limited mobility. However, a clear overestimation of the surface roughnesslimited mobility determined using semi-classical solvers is shown compared to NEGF results. These advanced solvers have been used to reproduce mobility measurements allowing us to calibrate Technology computer aided design (TCAD) mobility models.

TCAD modeling challenges for 14nm FullyDepleted SOI technology performance assessment

“…6 for RC in n and p-devices featuring various IL thicknesses [13]. Such a multi-scale approach [13] leads to TCAD models in agreement with split-CV mobility measurements performed in nMOS and pMOS for various interfacial charge densities, IL thicknesses and temperatures as summarized in Fig. 7 and Fig.…”

“…In backward regime (VB<0 for nMOS and VB>0 for pMOS), it increases the threshold voltage and reduce the leakage current. Additionally, front and back interfaces inversion can be controlled by the back-bias [13], [14]. Fig.…”

“…For the high value of stress applied in 14FD devices, nonlinear piezo approach such as MCMob is required [13] [16]. It is a stress-dependent mobility model implemented in Sentaurus Device simulator using a six-order polynomial fit of the electron and hole mobility variation along the channel direction.…”

“…Significant dependencies on the normal electric field on the mobility variation vs. strain are indeed observable for electrons and holes both in measurements and using advanced solved as described in [5]. For that reason, it is preferable to use Kubo-Greenwood mobility calculations based on 1D self-consistent Poisson k.p Schrödinger simulations as reported in [13]. In strained SiGe materials, Kubo Greenwood simulations accounting for alloyscattering and strain can also be used.…”

“…5. Full quantum NEGF solvers, describing scattering sources geometrically, have been used to confirm the validity of KG solvers applied to highly confined FDSOI structures [13]. Based on these much faster KG simulations, each TCAD mobility model parameters can be adjusted on a large set of geometries, temperatures, and scattering mechanisms as presented e.g.…”