[paper] DC, LF noise and TID mechanisms in 16nm FinFETs

Stefano Bonaldo^ab, Teng Ma^ab, Serena Mattiazzo^bc, Andrea Baschirotto^de, Christian Enz^f, Daniel M.Fleetwood^g, Alessandro Paccagnella^ab, Simone Gerardin^ab

DC response, low-frequency noise, and TID-induced mechanisms in 16-nm FinFETs for high-energy physics experiments

J. NIMA Section A; available online 18 April 2022, 166727

DOI: j.nima.2022.166727

     
a University of Padova (I)
b INFN Padova (I)
c University of Padova (I)
d INFN Milano (I)
e University of Milano Bicocca (I)
f ICLab, EPFL, Lausanne (CH)
g Vanderbilt University, Nashville (USA)

Abstract: Total-ionizing-dose (TID) mechanisms are evaluated in 16nm Si bulk FinFETs at doses up to 1 Grad (SiO₂) for applications in high-energy physics experiments. The TID effects are evaluated through DC and low-frequency noise measurements by varying irradiation bias conditions, transistor channel lengths, and fin/finger layouts. The TID response of nFinFETs irradiated under positive gate bias at ultrahigh doses shows a rebound of threshold voltage with significant increase in the 1/f noise amplitude. The degradation is related to the generation of border and interface traps at the upper corners of STI oxides and at the gate oxide/channel interfaces. In contrast, pFinFETs have the worst degradation due to positive charge trapping in STI oxides, which severely degrades the device transconductance and total drain current, while negligible effects are visible in the threshold voltage and 1/f noise. The TID sensitivity depends strongly on the transistor layout. Short-channel devices have the best TID tolerance thanks to the influence of halo implantation, while pFinFETs designed with low number of fins have the worst degradation because of high densities of positive charge in the surrounding thick STI oxides. As a guideline for IC design, short-channel transistors with more than 4-fins may be preferred in order to facilitate circuit qualification.

Fig: Low-frequency noise measured at |Vds|=50mV and |Vgs|=0.85V at room temperature for pFinFET with Nfin=2 and L=16 nm, irradiated up to 1Grad (SiO2) in the ON condition

Acknowledgment: This work has been carried out within the FinFET16v2 experiment funded by the National Institute for Nuclear Physics - INFN, Italy.

[paper] Generalized Devices for SPICE Simulation of Soft Errors

Chiara Rossi, André Chatel and Jean-Michel Sallese*

Modeling Funneling Effect With Generalized Devices for SPICE Simulation of Soft Errors

in IEEE Transactions on Electron Devices,

doi: 10.1109/TED.2021.3076028 

* EPFL, 1015 Lausanne (CH)

Abstract: Recent advances in CMOS scaling have made circuits more and more sensitive to errors and dysfunction caused by ionizing radiation, even at ground level, requiring accurate modeling of such effects. Besides generation, transport, and collection of radiation-induced excess carriers, another phenomenon, called funneling, has to be modeled for an accurate prediction of soft errors. The funneling effect occurs when the radiation track crosses a space charge region and generates excess carriers with a density higher than the doping close to it. These carriers distort the electric field of the space charge region, deeply changing the transport mechanism, from diffusion in a field-free semiconductor to drift. The objective of this work is to include funneling as part of the generalized lumped devices model in order to obtain a complete tool for SPICE-compatible simulations of single-event effects (SEEs). The latter approach has been recently proposed to simulate radiation-induced charges in the silicon substrate and is based on the so-called generalized lumped devices that simulate charge generation, propagation, and collection using standard circuit simulators. The generalized devices are here extended to include funneling and used to simulate an alpha particle impinging on the bulk of nMOS and pMOS transistors. The results obtained are validated with TCAD numerical simulations. Finally, a static random-access memory (SRAM) struck by an alpha particle is analyzed. The model predicts that the occurrence of a soft error, i.e., flipping of memory state, may depend on whether or not there is funneling. This justifies the need for accurate modeling of funneling phenomena to predict SEEs in ICs.

FIG: Generalized devices network obtained for the pMOS substrate. The mesh is drawn in gray dashed lines. The network is not shown around the radiation track; only the mesh is reported, which is denser to linearize the generation profile and excess carrier gradients.

Aknowlwdgement: This work was supported by the Swiss National Science Foundation (NSF) under Grant 200021_165773.