Large Injection Velocities in Highly Scaled, Fully Depleted Silicon on Insulator Transistors

Abstract

State-of-the-art Fully-Depleted Silicon-on-Insulator Transistors of different gate lengths were measured down to <inline-formula> <tex-math notation="LaTeX">${\text{L}}_{G}=20$ </tex-math></inline-formula> nm. A quasi-ballistic virtual source model was found to be in good agreement with the observed data for both NFET and PFET. The extracted injection velocity increases with decreasing channel length, as expected, reaching <inline-formula> <tex-math notation="LaTeX">${9.51}\times {10}^{{6}}\text {cm/s}$ </tex-math></inline-formula> for electrons and <inline-formula> <tex-math notation="LaTeX">${7.16}\times {10}^{{6}}\textit {cm/s}$ </tex-math></inline-formula> for holes at <inline-formula> <tex-math notation="LaTeX">${\text{L}}_{G}=20$ </tex-math></inline-formula> nm. These values are more than 80&#x0025; of the thermal velocity in lightly-doped bulk silicon. Analysis shows that quantum confinement in the thin SOI channel as well as strain effects are potentially responsible for such ultra-high velocity. These results indicate that further scaling of the channel length could make it possible to approach the non-degenerate thermal velocity.