Then, a very thin silicon film implements the transistor channel. Thanks to its thinness, there is no need to dope the channel, thus making the transistor fully depleted. The combination of these two innovations is called “ultra-thin body and buried oxide Fully Depleted SOI” or UTBB-FDSOI.
Back in 2013, CEA-Leti had deployed a first compact model, but working in close cooperation with STMicroelectronics, the research lab understood that more subtle back gate channelling effects had to be addressed to fully exploit the benefits of UTBB-FDSOI and to explore the transistors’ behaviour in more details.
New analytical equations were written from scratch for the Leti-UTSOI2.1 compact model, improving on the predictability and accuracy capabilities of the previous version, Leti-UTSOI2.
To date, other models from the University of Hiroshima, and from the University of Berkeley fail to account for inversion effects at the back interface, when a strong forward back bias (FBB) is applied, told us Thierry Poiroux, Leti research engineer and model co-developer.
More specifically, the French lab used a unique analytical resolution scheme for the calculation of surface potentials at both interfaces of the transistor body, offering a refined description of narrow-channel effects, with an improved accuracy of moderate inversion regime and gate tunnelling current modelling.
Because the model is analytical, it is much faster than any numerical simulation. It is now available in all major SPICE and Fast SPICE simulators through licences with EDA vendors and will allow fabless companies and IC designers to virtually explore different UTBB-FDSOI parameters within a given foundry process node. The new model can also be used by foundries and fabless companies to perform a predictive analysis of future nodes to come, in order to orient their ongoing process optimization.
for more information visit CEA-Leti at www.leti.fr